[PATCH v4] f2fs: introduce discard_granularity sysfs entry

[PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Chao Yu]

From: Chao Yu <yuchao0@huawei.com>

Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
f2fs to issue 4K size discard in real-time discard mode. However, issuing
smaller discard may cost more lifetime but releasing less free space in
flash device. Since f2fs has ability of separating hot/cold data and
garbage collection, we can expect that small-sized invalid region would
expand soon with OPU, deletion or garbage collection on valid datas, so
it's better to delay or skip issuing smaller size discards, it could help
to reduce overmuch consumption of IO bandwidth and lifetime of flash
storage.

This patch makes f2fs selectng 64K size as its default minimal
granularity, and issue discard with the size which is not smaller than
minimal granularity. Also it exposes discard granularity as sysfs entry
for configuration in different scenario.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
v4: minor change in commit log.
 Documentation/ABI/testing/sysfs-fs-f2fs |  9 +++++++++
 fs/f2fs/f2fs.h                          |  4 ++++
 fs/f2fs/segment.c                       | 23 ++++++++++++++++++++++-
 fs/f2fs/sysfs.c                         |  7 +++++++
 4 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 84c606fb3ca4..c579ce5e0ef5 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -57,6 +57,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
 Description:
 		 Controls the issue rate of small discard commands.
 
+What:          /sys/fs/f2fs/<disk>/discard_granularity
+Date:          July 2017
+Contact:       "Chao Yu" <yuchao0@huawei.com>
+Description:
+		Controls discard granularity of inner discard thread, inner thread
+		will not issue discards with size that is smaller than granularity.
+		The unit size is one block, now only support configuring in range
+		of [1, 512].
+
 What:		/sys/fs/f2fs/<disk>/max_victim_search
 Date:		January 2014
 Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 0ccccbfdeeab..1bcaa93bfed7 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -195,6 +195,9 @@ struct discard_entry {
 	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
 };
 
+/* default discard granularity of inner discard thread, unit: block count */
+#define DEFAULT_DISCARD_GRANULARITY		16
+
 /* max discard pend list number */
 #define MAX_PLIST_NUM		512
 #define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
@@ -240,6 +243,7 @@ struct discard_cmd_control {
 	struct mutex cmd_lock;
 	unsigned int nr_discards;		/* # of discards in the list */
 	unsigned int max_discards;		/* max. discards to be issued */
+	unsigned int discard_granularity;	/* discard granularity */
 	unsigned int undiscard_blks;		/* # of undiscard blocks */
 	atomic_t issued_discard;		/* # of issued discard */
 	atomic_t issing_discard;		/* # of issing discard */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 71c2e0ac13d7..f336f8c541f0 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1019,7 +1019,8 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
 	f2fs_bug_on(sbi,
 		!__check_rb_tree_consistence(sbi, &dcc->root));
 	blk_start_plug(&plug);
-	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+	for (i = MAX_PLIST_NUM - 1; i >= 0 &&
+			i >= dcc->discard_granularity - 1; i--) {
 		pend_list = &dcc->pend_list[i];
 		list_for_each_entry_safe(dc, tmp, pend_list, list) {
 			f2fs_bug_on(sbi, dc->state != D_PREP);
@@ -1035,6 +1036,24 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
 	mutex_unlock(&dcc->cmd_lock);
 }
 
+static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
+{
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	struct list_head *pend_list;
+	struct discard_cmd *dc, *tmp;
+	int i;
+
+	mutex_lock(&dcc->cmd_lock);
+	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+		pend_list = &dcc->pend_list[i];
+		list_for_each_entry_safe(dc, tmp, pend_list, list) {
+			f2fs_bug_on(sbi, dc->state != D_PREP);
+			__remove_discard_cmd(sbi, dc);
+		}
+	}
+	mutex_unlock(&dcc->cmd_lock);
+}
+
 static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
 							struct discard_cmd *dc)
 {
@@ -1117,6 +1136,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
 void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
 {
 	__issue_discard_cmd(sbi, false);
+	__drop_discard_cmd(sbi);
 	__wait_discard_cmd(sbi, false);
 }
 
@@ -1449,6 +1469,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 	atomic_set(&dcc->discard_cmd_cnt, 0);
 	dcc->nr_discards = 0;
 	dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
+	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
 	dcc->undiscard_blks = 0;
 	dcc->root = RB_ROOT;
 
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 045b948c7466..4e5a95e9e666 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -152,6 +152,11 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 		spin_unlock(&sbi->stat_lock);
 		return count;
 	}
+
+	if (!strcmp(a->attr.name, "discard_granularity") &&
+					(t == 0 || t > MAX_PLIST_NUM))
+		return -EINVAL;
+
 	*ui = t;
 
 	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
@@ -241,6 +246,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
+F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
 F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
@@ -281,6 +287,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(gc_idle),
 	ATTR_LIST(reclaim_segments),
 	ATTR_LIST(max_small_discards),
+	ATTR_LIST(discard_granularity),
 	ATTR_LIST(batched_trim_sections),
 	ATTR_LIST(ipu_policy),
 	ATTR_LIST(min_ipu_util),
-- 
2.14.0

Re: [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Jaegeuk Kim]

On 08/07, Chao Yu wrote:
> From: Chao Yu <yuchao0@huawei.com>
> 
> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
> f2fs to issue 4K size discard in real-time discard mode. However, issuing
> smaller discard may cost more lifetime but releasing less free space in
> flash device. Since f2fs has ability of separating hot/cold data and
> garbage collection, we can expect that small-sized invalid region would
> expand soon with OPU, deletion or garbage collection on valid datas, so
> it's better to delay or skip issuing smaller size discards, it could help
> to reduce overmuch consumption of IO bandwidth and lifetime of flash
> storage.
> 
> This patch makes f2fs selectng 64K size as its default minimal
> granularity, and issue discard with the size which is not smaller than
> minimal granularity. Also it exposes discard granularity as sysfs entry
> for configuration in different scenario.

Hi Chao,

I'd like to change the default value to 1 in order to keep the original
behavior, since we must avoid performance fluctuation after this single
patch. Instead, you probably can change the value through sysfs.

Thanks,

> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
> v4: minor change in commit log.
>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 +++++++++
>  fs/f2fs/f2fs.h                          |  4 ++++
>  fs/f2fs/segment.c                       | 23 ++++++++++++++++++++++-
>  fs/f2fs/sysfs.c                         |  7 +++++++
>  4 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 84c606fb3ca4..c579ce5e0ef5 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -57,6 +57,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>  Description:
>  		 Controls the issue rate of small discard commands.
>  
> +What:          /sys/fs/f2fs/<disk>/discard_granularity
> +Date:          July 2017
> +Contact:       "Chao Yu" <yuchao0@huawei.com>
> +Description:
> +		Controls discard granularity of inner discard thread, inner thread
> +		will not issue discards with size that is smaller than granularity.
> +		The unit size is one block, now only support configuring in range
> +		of [1, 512].
> +
>  What:		/sys/fs/f2fs/<disk>/max_victim_search
>  Date:		January 2014
>  Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 0ccccbfdeeab..1bcaa93bfed7 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -195,6 +195,9 @@ struct discard_entry {
>  	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
>  };
>  
> +/* default discard granularity of inner discard thread, unit: block count */
> +#define DEFAULT_DISCARD_GRANULARITY		16
> +
>  /* max discard pend list number */
>  #define MAX_PLIST_NUM		512
>  #define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
> @@ -240,6 +243,7 @@ struct discard_cmd_control {
>  	struct mutex cmd_lock;
>  	unsigned int nr_discards;		/* # of discards in the list */
>  	unsigned int max_discards;		/* max. discards to be issued */
> +	unsigned int discard_granularity;	/* discard granularity */
>  	unsigned int undiscard_blks;		/* # of undiscard blocks */
>  	atomic_t issued_discard;		/* # of issued discard */
>  	atomic_t issing_discard;		/* # of issing discard */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 71c2e0ac13d7..f336f8c541f0 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1019,7 +1019,8 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>  	f2fs_bug_on(sbi,
>  		!__check_rb_tree_consistence(sbi, &dcc->root));
>  	blk_start_plug(&plug);
> -	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> +	for (i = MAX_PLIST_NUM - 1; i >= 0 &&
> +			i >= dcc->discard_granularity - 1; i--) {
>  		pend_list = &dcc->pend_list[i];
>  		list_for_each_entry_safe(dc, tmp, pend_list, list) {
>  			f2fs_bug_on(sbi, dc->state != D_PREP);
> @@ -1035,6 +1036,24 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>  	mutex_unlock(&dcc->cmd_lock);
>  }
>  
> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
> +{
> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +	struct list_head *pend_list;
> +	struct discard_cmd *dc, *tmp;
> +	int i;
> +
> +	mutex_lock(&dcc->cmd_lock);
> +	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> +		pend_list = &dcc->pend_list[i];
> +		list_for_each_entry_safe(dc, tmp, pend_list, list) {
> +			f2fs_bug_on(sbi, dc->state != D_PREP);
> +			__remove_discard_cmd(sbi, dc);
> +		}
> +	}
> +	mutex_unlock(&dcc->cmd_lock);
> +}
> +
>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>  							struct discard_cmd *dc)
>  {
> @@ -1117,6 +1136,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>  {
>  	__issue_discard_cmd(sbi, false);
> +	__drop_discard_cmd(sbi);
>  	__wait_discard_cmd(sbi, false);
>  }
>  
> @@ -1449,6 +1469,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>  	atomic_set(&dcc->discard_cmd_cnt, 0);
>  	dcc->nr_discards = 0;
>  	dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
> +	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>  	dcc->undiscard_blks = 0;
>  	dcc->root = RB_ROOT;
>  
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 045b948c7466..4e5a95e9e666 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -152,6 +152,11 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>  		spin_unlock(&sbi->stat_lock);
>  		return count;
>  	}
> +
> +	if (!strcmp(a->attr.name, "discard_granularity") &&
> +					(t == 0 || t > MAX_PLIST_NUM))
> +		return -EINVAL;
> +
>  	*ui = t;
>  
>  	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
> @@ -241,6 +246,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
> @@ -281,6 +287,7 @@ static struct attribute *f2fs_attrs[] = {
>  	ATTR_LIST(gc_idle),
>  	ATTR_LIST(reclaim_segments),
>  	ATTR_LIST(max_small_discards),
> +	ATTR_LIST(discard_granularity),
>  	ATTR_LIST(batched_trim_sections),
>  	ATTR_LIST(ipu_policy),
>  	ATTR_LIST(min_ipu_util),
> -- 
> 2.14.0

Re: [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Chao Yu]

On 2017/8/15 11:45, Jaegeuk Kim wrote:
> On 08/07, Chao Yu wrote:
>> From: Chao Yu <yuchao0@huawei.com>
>>
>> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
>> f2fs to issue 4K size discard in real-time discard mode. However, issuing
>> smaller discard may cost more lifetime but releasing less free space in
>> flash device. Since f2fs has ability of separating hot/cold data and
>> garbage collection, we can expect that small-sized invalid region would
>> expand soon with OPU, deletion or garbage collection on valid datas, so
>> it's better to delay or skip issuing smaller size discards, it could help
>> to reduce overmuch consumption of IO bandwidth and lifetime of flash
>> storage.
>>
>> This patch makes f2fs selectng 64K size as its default minimal
>> granularity, and issue discard with the size which is not smaller than
>> minimal granularity. Also it exposes discard granularity as sysfs entry
>> for configuration in different scenario.
> 
> Hi Chao,
> 
> I'd like to change the default value to 1 in order to keep the original
> behavior, since we must avoid performance fluctuation after this single
> patch. Instead, you probably can change the value through sysfs.

As I know, in fragmented filesystem space, there are may dozens of thousand
discard, in scenario of cellphone user are using, 30% is above 64K size, but
occupy 75% space of all undiscard space, so I changed discard_granularity to 64K
just to release bulk space in device. For other small-sized discards, I expect
that they may extend and cross the granularity threshold soon, and fstrim of
android could cover them in the night.

Do you encounter performance degression due to holding 64k-below size discard?

thank,

> 
> Thanks,
> 
>>
>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>> ---
>> v4: minor change in commit log.
>>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 +++++++++
>>  fs/f2fs/f2fs.h                          |  4 ++++
>>  fs/f2fs/segment.c                       | 23 ++++++++++++++++++++++-
>>  fs/f2fs/sysfs.c                         |  7 +++++++
>>  4 files changed, 42 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>> index 84c606fb3ca4..c579ce5e0ef5 100644
>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>> @@ -57,6 +57,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>>  Description:
>>  		 Controls the issue rate of small discard commands.
>>  
>> +What:          /sys/fs/f2fs/<disk>/discard_granularity
>> +Date:          July 2017
>> +Contact:       "Chao Yu" <yuchao0@huawei.com>
>> +Description:
>> +		Controls discard granularity of inner discard thread, inner thread
>> +		will not issue discards with size that is smaller than granularity.
>> +		The unit size is one block, now only support configuring in range
>> +		of [1, 512].
>> +
>>  What:		/sys/fs/f2fs/<disk>/max_victim_search
>>  Date:		January 2014
>>  Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 0ccccbfdeeab..1bcaa93bfed7 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -195,6 +195,9 @@ struct discard_entry {
>>  	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
>>  };
>>  
>> +/* default discard granularity of inner discard thread, unit: block count */
>> +#define DEFAULT_DISCARD_GRANULARITY		16
>> +
>>  /* max discard pend list number */
>>  #define MAX_PLIST_NUM		512
>>  #define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
>> @@ -240,6 +243,7 @@ struct discard_cmd_control {
>>  	struct mutex cmd_lock;
>>  	unsigned int nr_discards;		/* # of discards in the list */
>>  	unsigned int max_discards;		/* max. discards to be issued */
>> +	unsigned int discard_granularity;	/* discard granularity */
>>  	unsigned int undiscard_blks;		/* # of undiscard blocks */
>>  	atomic_t issued_discard;		/* # of issued discard */
>>  	atomic_t issing_discard;		/* # of issing discard */
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 71c2e0ac13d7..f336f8c541f0 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -1019,7 +1019,8 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>  	f2fs_bug_on(sbi,
>>  		!__check_rb_tree_consistence(sbi, &dcc->root));
>>  	blk_start_plug(&plug);
>> -	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>> +	for (i = MAX_PLIST_NUM - 1; i >= 0 &&
>> +			i >= dcc->discard_granularity - 1; i--) {
>>  		pend_list = &dcc->pend_list[i];
>>  		list_for_each_entry_safe(dc, tmp, pend_list, list) {
>>  			f2fs_bug_on(sbi, dc->state != D_PREP);
>> @@ -1035,6 +1036,24 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>  	mutex_unlock(&dcc->cmd_lock);
>>  }
>>  
>> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
>> +{
>> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>> +	struct list_head *pend_list;
>> +	struct discard_cmd *dc, *tmp;
>> +	int i;
>> +
>> +	mutex_lock(&dcc->cmd_lock);
>> +	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>> +		pend_list = &dcc->pend_list[i];
>> +		list_for_each_entry_safe(dc, tmp, pend_list, list) {
>> +			f2fs_bug_on(sbi, dc->state != D_PREP);
>> +			__remove_discard_cmd(sbi, dc);
>> +		}
>> +	}
>> +	mutex_unlock(&dcc->cmd_lock);
>> +}
>> +
>>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>>  							struct discard_cmd *dc)
>>  {
>> @@ -1117,6 +1136,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>>  {
>>  	__issue_discard_cmd(sbi, false);
>> +	__drop_discard_cmd(sbi);
>>  	__wait_discard_cmd(sbi, false);
>>  }
>>  
>> @@ -1449,6 +1469,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>  	atomic_set(&dcc->discard_cmd_cnt, 0);
>>  	dcc->nr_discards = 0;
>>  	dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
>> +	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>>  	dcc->undiscard_blks = 0;
>>  	dcc->root = RB_ROOT;
>>  
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index 045b948c7466..4e5a95e9e666 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -152,6 +152,11 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>  		spin_unlock(&sbi->stat_lock);
>>  		return count;
>>  	}
>> +
>> +	if (!strcmp(a->attr.name, "discard_granularity") &&
>> +					(t == 0 || t > MAX_PLIST_NUM))
>> +		return -EINVAL;
>> +
>>  	*ui = t;
>>  
>>  	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
>> @@ -241,6 +246,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
>>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
>> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
>> @@ -281,6 +287,7 @@ static struct attribute *f2fs_attrs[] = {
>>  	ATTR_LIST(gc_idle),
>>  	ATTR_LIST(reclaim_segments),
>>  	ATTR_LIST(max_small_discards),
>> +	ATTR_LIST(discard_granularity),
>>  	ATTR_LIST(batched_trim_sections),
>>  	ATTR_LIST(ipu_policy),
>>  	ATTR_LIST(min_ipu_util),
>> -- 
>> 2.14.0
> 
> .
> 

Re: [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Jaegeuk Kim]

On 08/15, Chao Yu wrote:
> On 2017/8/15 11:45, Jaegeuk Kim wrote:
> > On 08/07, Chao Yu wrote:
> >> From: Chao Yu <yuchao0@huawei.com>
> >>
> >> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
> >> f2fs to issue 4K size discard in real-time discard mode. However, issuing
> >> smaller discard may cost more lifetime but releasing less free space in
> >> flash device. Since f2fs has ability of separating hot/cold data and
> >> garbage collection, we can expect that small-sized invalid region would
> >> expand soon with OPU, deletion or garbage collection on valid datas, so
> >> it's better to delay or skip issuing smaller size discards, it could help
> >> to reduce overmuch consumption of IO bandwidth and lifetime of flash
> >> storage.
> >>
> >> This patch makes f2fs selectng 64K size as its default minimal
> >> granularity, and issue discard with the size which is not smaller than
> >> minimal granularity. Also it exposes discard granularity as sysfs entry
> >> for configuration in different scenario.
> > 
> > Hi Chao,
> > 
> > I'd like to change the default value to 1 in order to keep the original
> > behavior, since we must avoid performance fluctuation after this single
> > patch. Instead, you probably can change the value through sysfs.
> 
> As I know, in fragmented filesystem space, there are may dozens of thousand
> discard, in scenario of cellphone user are using, 30% is above 64K size, but
> occupy 75% space of all undiscard space, so I changed discard_granularity to 64K
> just to release bulk space in device. For other small-sized discards, I expect
> that they may extend and cross the granularity threshold soon, and fstrim of
> android could cover them in the night.

Yup, I thought that, but this patch prevents fstrim from issuing small discards
due to the granularity check. And, low-end device likes to issue small discards
much more. How about this?

>From a0f38a8574a35995ba9e9e81ae5138919bb672a8 Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@huawei.com>
Date: Mon, 7 Aug 2017 23:09:56 +0800
Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry

Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
f2fs to issue 4K size discard in real-time discard mode. However, issuing
smaller discard may cost more lifetime but releasing less free space in
flash device. Since f2fs has ability of separating hot/cold data and
garbage collection, we can expect that small-sized invalid region would
expand soon with OPU, deletion or garbage collection on valid datas, so
it's better to delay or skip issuing smaller size discards, it could help
to reduce overmuch consumption of IO bandwidth and lifetime of flash
storage.

This patch makes f2fs selectng 64K size as its default minimal
granularity, and issue discard with the size which is not smaller than
minimal granularity. Also it exposes discard granularity as sysfs entry
for configuration in different scenario.

Jaegeuk Kim:
 We must issue all the accumulated discard commands when fstrim is called.
 So, I've added pend_list_tag[] to indicate whether we should issue the
 commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
 P_TRIM is set once at a time, given fstrim trigger.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 Documentation/ABI/testing/sysfs-fs-f2fs |  9 +++++++
 fs/f2fs/f2fs.h                          |  9 +++++++
 fs/f2fs/segment.c                       | 43 +++++++++++++++++++++++++++++++--
 fs/f2fs/sysfs.c                         | 23 ++++++++++++++++++
 4 files changed, 82 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 621da3fc56c5..11b7f4ebea7c 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -57,6 +57,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
 Description:
 		 Controls the issue rate of small discard commands.
 
+What:          /sys/fs/f2fs/<disk>/discard_granularity
+Date:          July 2017
+Contact:       "Chao Yu" <yuchao0@huawei.com>
+Description:
+		Controls discard granularity of inner discard thread, inner thread
+		will not issue discards with size that is smaller than granularity.
+		The unit size is one block, now only support configuring in range
+		of [1, 512].
+
 What:		/sys/fs/f2fs/<disk>/max_victim_search
 Date:		January 2014
 Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e252e5bf9791..336021b9b93e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -196,11 +196,18 @@ struct discard_entry {
 	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
 };
 
+/* default discard granularity of inner discard thread, unit: block count */
+#define DEFAULT_DISCARD_GRANULARITY		16
+
 /* max discard pend list number */
 #define MAX_PLIST_NUM		512
 #define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
 					(MAX_PLIST_NUM - 1) : (blk_num - 1))
 
+#define P_ACTIVE	0x01
+#define P_TRIM		0x02
+#define plist_issue(tag)	(((tag) & P_ACTIVE) || ((tag) & P_TRIM))
+
 enum {
 	D_PREP,
 	D_SUBMIT,
@@ -236,11 +243,13 @@ struct discard_cmd_control {
 	struct task_struct *f2fs_issue_discard;	/* discard thread */
 	struct list_head entry_list;		/* 4KB discard entry list */
 	struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
+	unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
 	struct list_head wait_list;		/* store on-flushing entries */
 	wait_queue_head_t discard_wait_queue;	/* waiting queue for wake-up */
 	struct mutex cmd_lock;
 	unsigned int nr_discards;		/* # of discards in the list */
 	unsigned int max_discards;		/* max. discards to be issued */
+	unsigned int discard_granularity;	/* discard granularity */
 	unsigned int undiscard_blks;		/* # of undiscard blocks */
 	atomic_t issued_discard;		/* # of issued discard */
 	atomic_t issing_discard;		/* # of issing discard */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 05144b3a7f62..8c90b69dcd6d 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1028,22 +1028,49 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
 	f2fs_bug_on(sbi,
 		!__check_rb_tree_consistence(sbi, &dcc->root));
 	blk_start_plug(&plug);
-	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+	for (i = MAX_PLIST_NUM - 1;
+			i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
 		pend_list = &dcc->pend_list[i];
 		list_for_each_entry_safe(dc, tmp, pend_list, list) {
 			f2fs_bug_on(sbi, dc->state != D_PREP);
 
+			/* Hurry up to finish fstrim */
+			if (dcc->pend_list_tag[i] & P_TRIM) {
+				__submit_discard_cmd(sbi, dc);
+				continue;
+			}
+
 			if (!issue_cond || is_idle(sbi))
 				__submit_discard_cmd(sbi, dc);
 			if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
 				goto out;
 		}
+		if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
+			dcc->pend_list_tag[i] &= (~P_TRIM);
 	}
 out:
 	blk_finish_plug(&plug);
 	mutex_unlock(&dcc->cmd_lock);
 }
 
+static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
+{
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	struct list_head *pend_list;
+	struct discard_cmd *dc, *tmp;
+	int i;
+
+	mutex_lock(&dcc->cmd_lock);
+	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+		pend_list = &dcc->pend_list[i];
+		list_for_each_entry_safe(dc, tmp, pend_list, list) {
+			f2fs_bug_on(sbi, dc->state != D_PREP);
+			__remove_discard_cmd(sbi, dc);
+		}
+	}
+	mutex_unlock(&dcc->cmd_lock);
+}
+
 static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
 							struct discard_cmd *dc)
 {
@@ -1126,6 +1153,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
 void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
 {
 	__issue_discard_cmd(sbi, false);
+	__drop_discard_cmd(sbi);
 	__wait_discard_cmd(sbi, false);
 }
 
@@ -1448,9 +1476,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 	if (!dcc)
 		return -ENOMEM;
 
+	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
 	INIT_LIST_HEAD(&dcc->entry_list);
-	for (i = 0; i < MAX_PLIST_NUM; i++)
+	for (i = 0; i < MAX_PLIST_NUM; i++) {
 		INIT_LIST_HEAD(&dcc->pend_list[i]);
+		if (i >= dcc->discard_granularity - 1)
+			dcc->pend_list_tag[i] |= P_ACTIVE;
+	}
 	INIT_LIST_HEAD(&dcc->wait_list);
 	mutex_init(&dcc->cmd_lock);
 	atomic_set(&dcc->issued_discard, 0);
@@ -2079,11 +2111,13 @@ bool exist_trim_candidates(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
 int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 {
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 	__u64 start = F2FS_BYTES_TO_BLK(range->start);
 	__u64 end = start + F2FS_BYTES_TO_BLK(range->len) - 1;
 	unsigned int start_segno, end_segno;
 	struct cp_control cpc;
 	int err = 0;
+	int i;
 
 	if (start >= MAX_BLKADDR(sbi) || range->len < sbi->blocksize)
 		return -EINVAL;
@@ -2127,6 +2161,11 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 
 		schedule();
 	}
+	/* It's time to issue all the filed discards */
+	mutex_lock(&dcc->cmd_lock);
+	for (i = 0; i < MAX_PLIST_NUM; i++)
+		dcc->pend_list_tag[i] |= P_TRIM;
+	mutex_unlock(&dcc->cmd_lock);
 out:
 	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
 	return err;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index c40e5d24df9f..4bcaa9059026 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 		spin_unlock(&sbi->stat_lock);
 		return count;
 	}
+
+	if (!strcmp(a->attr.name, "discard_granularity")) {
+		struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+		int i;
+
+		if (t == 0 || t > MAX_PLIST_NUM)
+			return -EINVAL;
+		if (t == *ui)
+			return count;
+
+		mutex_lock(&dcc->cmd_lock);
+		for (i = 0; i < MAX_PLIST_NUM; i++) {
+			if (i >= t - 1)
+				dcc->pend_list_tag[i] |= P_ACTIVE;
+			else
+				dcc->pend_list_tag[i] &= (~P_ACTIVE);
+		}
+		mutex_unlock(&dcc->cmd_lock);
+		return count;
+	}
+
 	*ui = t;
 
 	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
@@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
+F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
 F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
@@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(gc_urgent),
 	ATTR_LIST(reclaim_segments),
 	ATTR_LIST(max_small_discards),
+	ATTR_LIST(discard_granularity),
 	ATTR_LIST(batched_trim_sections),
 	ATTR_LIST(ipu_policy),
 	ATTR_LIST(min_ipu_util),
-- 
2.14.0.rc1.383.gd1ce394fe2-goog

Re: [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Chao Yu]

Hi Jaegeuk,

Sorry for the delay, the modification looks good to me. ;)

Thanks,

On 2017/8/16 1:54, Jaegeuk Kim wrote:
> On 08/15, Chao Yu wrote:
>> On 2017/8/15 11:45, Jaegeuk Kim wrote:
>>> On 08/07, Chao Yu wrote:
>>>> From: Chao Yu <yuchao0@huawei.com>
>>>>
>>>> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
>>>> f2fs to issue 4K size discard in real-time discard mode. However, issuing
>>>> smaller discard may cost more lifetime but releasing less free space in
>>>> flash device. Since f2fs has ability of separating hot/cold data and
>>>> garbage collection, we can expect that small-sized invalid region would
>>>> expand soon with OPU, deletion or garbage collection on valid datas, so
>>>> it's better to delay or skip issuing smaller size discards, it could help
>>>> to reduce overmuch consumption of IO bandwidth and lifetime of flash
>>>> storage.
>>>>
>>>> This patch makes f2fs selectng 64K size as its default minimal
>>>> granularity, and issue discard with the size which is not smaller than
>>>> minimal granularity. Also it exposes discard granularity as sysfs entry
>>>> for configuration in different scenario.
>>>
>>> Hi Chao,
>>>
>>> I'd like to change the default value to 1 in order to keep the original
>>> behavior, since we must avoid performance fluctuation after this single
>>> patch. Instead, you probably can change the value through sysfs.
>>
>> As I know, in fragmented filesystem space, there are may dozens of thousand
>> discard, in scenario of cellphone user are using, 30% is above 64K size, but
>> occupy 75% space of all undiscard space, so I changed discard_granularity to 64K
>> just to release bulk space in device. For other small-sized discards, I expect
>> that they may extend and cross the granularity threshold soon, and fstrim of
>> android could cover them in the night.
> 
> Yup, I thought that, but this patch prevents fstrim from issuing small discards
> due to the granularity check. And, low-end device likes to issue small discards
> much more. How about this?
> 
> From a0f38a8574a35995ba9e9e81ae5138919bb672a8 Mon Sep 17 00:00:00 2001
> From: Chao Yu <yuchao0@huawei.com>
> Date: Mon, 7 Aug 2017 23:09:56 +0800
> Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry
> 
> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
> f2fs to issue 4K size discard in real-time discard mode. However, issuing
> smaller discard may cost more lifetime but releasing less free space in
> flash device. Since f2fs has ability of separating hot/cold data and
> garbage collection, we can expect that small-sized invalid region would
> expand soon with OPU, deletion or garbage collection on valid datas, so
> it's better to delay or skip issuing smaller size discards, it could help
> to reduce overmuch consumption of IO bandwidth and lifetime of flash
> storage.
> 
> This patch makes f2fs selectng 64K size as its default minimal
> granularity, and issue discard with the size which is not smaller than
> minimal granularity. Also it exposes discard granularity as sysfs entry
> for configuration in different scenario.
> 
> Jaegeuk Kim:
>  We must issue all the accumulated discard commands when fstrim is called.
>  So, I've added pend_list_tag[] to indicate whether we should issue the
>  commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
>  P_TRIM is set once at a time, given fstrim trigger.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 +++++++
>  fs/f2fs/f2fs.h                          |  9 +++++++
>  fs/f2fs/segment.c                       | 43 +++++++++++++++++++++++++++++++--
>  fs/f2fs/sysfs.c                         | 23 ++++++++++++++++++
>  4 files changed, 82 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 621da3fc56c5..11b7f4ebea7c 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -57,6 +57,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>  Description:
>  		 Controls the issue rate of small discard commands.
>  
> +What:          /sys/fs/f2fs/<disk>/discard_granularity
> +Date:          July 2017
> +Contact:       "Chao Yu" <yuchao0@huawei.com>
> +Description:
> +		Controls discard granularity of inner discard thread, inner thread
> +		will not issue discards with size that is smaller than granularity.
> +		The unit size is one block, now only support configuring in range
> +		of [1, 512].
> +
>  What:		/sys/fs/f2fs/<disk>/max_victim_search
>  Date:		January 2014
>  Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e252e5bf9791..336021b9b93e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -196,11 +196,18 @@ struct discard_entry {
>  	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
>  };
>  
> +/* default discard granularity of inner discard thread, unit: block count */
> +#define DEFAULT_DISCARD_GRANULARITY		16
> +
>  /* max discard pend list number */
>  #define MAX_PLIST_NUM		512
>  #define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
>  					(MAX_PLIST_NUM - 1) : (blk_num - 1))
>  
> +#define P_ACTIVE	0x01
> +#define P_TRIM		0x02
> +#define plist_issue(tag)	(((tag) & P_ACTIVE) || ((tag) & P_TRIM))
> +
>  enum {
>  	D_PREP,
>  	D_SUBMIT,
> @@ -236,11 +243,13 @@ struct discard_cmd_control {
>  	struct task_struct *f2fs_issue_discard;	/* discard thread */
>  	struct list_head entry_list;		/* 4KB discard entry list */
>  	struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
> +	unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
>  	struct list_head wait_list;		/* store on-flushing entries */
>  	wait_queue_head_t discard_wait_queue;	/* waiting queue for wake-up */
>  	struct mutex cmd_lock;
>  	unsigned int nr_discards;		/* # of discards in the list */
>  	unsigned int max_discards;		/* max. discards to be issued */
> +	unsigned int discard_granularity;	/* discard granularity */
>  	unsigned int undiscard_blks;		/* # of undiscard blocks */
>  	atomic_t issued_discard;		/* # of issued discard */
>  	atomic_t issing_discard;		/* # of issing discard */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 05144b3a7f62..8c90b69dcd6d 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1028,22 +1028,49 @@ static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>  	f2fs_bug_on(sbi,
>  		!__check_rb_tree_consistence(sbi, &dcc->root));
>  	blk_start_plug(&plug);
> -	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> +	for (i = MAX_PLIST_NUM - 1;
> +			i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
>  		pend_list = &dcc->pend_list[i];
>  		list_for_each_entry_safe(dc, tmp, pend_list, list) {
>  			f2fs_bug_on(sbi, dc->state != D_PREP);
>  
> +			/* Hurry up to finish fstrim */
> +			if (dcc->pend_list_tag[i] & P_TRIM) {
> +				__submit_discard_cmd(sbi, dc);
> +				continue;
> +			}
> +
>  			if (!issue_cond || is_idle(sbi))
>  				__submit_discard_cmd(sbi, dc);
>  			if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
>  				goto out;
>  		}
> +		if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
> +			dcc->pend_list_tag[i] &= (~P_TRIM);
>  	}
>  out:
>  	blk_finish_plug(&plug);
>  	mutex_unlock(&dcc->cmd_lock);
>  }
>  
> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
> +{
> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +	struct list_head *pend_list;
> +	struct discard_cmd *dc, *tmp;
> +	int i;
> +
> +	mutex_lock(&dcc->cmd_lock);
> +	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> +		pend_list = &dcc->pend_list[i];
> +		list_for_each_entry_safe(dc, tmp, pend_list, list) {
> +			f2fs_bug_on(sbi, dc->state != D_PREP);
> +			__remove_discard_cmd(sbi, dc);
> +		}
> +	}
> +	mutex_unlock(&dcc->cmd_lock);
> +}
> +
>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>  							struct discard_cmd *dc)
>  {
> @@ -1126,6 +1153,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>  {
>  	__issue_discard_cmd(sbi, false);
> +	__drop_discard_cmd(sbi);
>  	__wait_discard_cmd(sbi, false);
>  }
>  
> @@ -1448,9 +1476,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>  	if (!dcc)
>  		return -ENOMEM;
>  
> +	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>  	INIT_LIST_HEAD(&dcc->entry_list);
> -	for (i = 0; i < MAX_PLIST_NUM; i++)
> +	for (i = 0; i < MAX_PLIST_NUM; i++) {
>  		INIT_LIST_HEAD(&dcc->pend_list[i]);
> +		if (i >= dcc->discard_granularity - 1)
> +			dcc->pend_list_tag[i] |= P_ACTIVE;
> +	}
>  	INIT_LIST_HEAD(&dcc->wait_list);
>  	mutex_init(&dcc->cmd_lock);
>  	atomic_set(&dcc->issued_discard, 0);
> @@ -2079,11 +2111,13 @@ bool exist_trim_candidates(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  
>  int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  {
> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>  	__u64 start = F2FS_BYTES_TO_BLK(range->start);
>  	__u64 end = start + F2FS_BYTES_TO_BLK(range->len) - 1;
>  	unsigned int start_segno, end_segno;
>  	struct cp_control cpc;
>  	int err = 0;
> +	int i;
>  
>  	if (start >= MAX_BLKADDR(sbi) || range->len < sbi->blocksize)
>  		return -EINVAL;
> @@ -2127,6 +2161,11 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  
>  		schedule();
>  	}
> +	/* It's time to issue all the filed discards */
> +	mutex_lock(&dcc->cmd_lock);
> +	for (i = 0; i < MAX_PLIST_NUM; i++)
> +		dcc->pend_list_tag[i] |= P_TRIM;
> +	mutex_unlock(&dcc->cmd_lock);
>  out:
>  	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>  	return err;
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index c40e5d24df9f..4bcaa9059026 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>  		spin_unlock(&sbi->stat_lock);
>  		return count;
>  	}
> +
> +	if (!strcmp(a->attr.name, "discard_granularity")) {
> +		struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +		int i;
> +
> +		if (t == 0 || t > MAX_PLIST_NUM)
> +			return -EINVAL;
> +		if (t == *ui)
> +			return count;
> +
> +		mutex_lock(&dcc->cmd_lock);
> +		for (i = 0; i < MAX_PLIST_NUM; i++) {
> +			if (i >= t - 1)
> +				dcc->pend_list_tag[i] |= P_ACTIVE;
> +			else
> +				dcc->pend_list_tag[i] &= (~P_ACTIVE);
> +		}
> +		mutex_unlock(&dcc->cmd_lock);
> +		return count;
> +	}
> +
>  	*ui = t;
>  
>  	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
> @@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
> @@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
>  	ATTR_LIST(gc_urgent),
>  	ATTR_LIST(reclaim_segments),
>  	ATTR_LIST(max_small_discards),
> +	ATTR_LIST(discard_granularity),
>  	ATTR_LIST(batched_trim_sections),
>  	ATTR_LIST(ipu_policy),
>  	ATTR_LIST(min_ipu_util),
> 

Re: [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Jaegeuk Kim]

On 08/18, Chao Yu wrote:
> Hi Jaegeuk,
> 
> Sorry for the delay, the modification looks good to me. ;)

We must avoid waking up discard thread caused by # of pending commands
which are never issued.

>From a73f8807248c2f42328a2204eab16a3b8d32c83e Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@huawei.com>
Date: Mon, 7 Aug 2017 23:09:56 +0800
Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry

Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
f2fs to issue 4K size discard in real-time discard mode. However, issuing
smaller discard may cost more lifetime but releasing less free space in
flash device. Since f2fs has ability of separating hot/cold data and
garbage collection, we can expect that small-sized invalid region would
expand soon with OPU, deletion or garbage collection on valid datas, so
it's better to delay or skip issuing smaller size discards, it could help
to reduce overmuch consumption of IO bandwidth and lifetime of flash
storage.

This patch makes f2fs selectng 64K size as its default minimal
granularity, and issue discard with the size which is not smaller than
minimal granularity. Also it exposes discard granularity as sysfs entry
for configuration in different scenario.

Jaegeuk Kim:
 We must issue all the accumulated discard commands when fstrim is called.
 So, I've added pend_list_tag[] to indicate whether we should issue the
 commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
 P_TRIM is set once at a time, given fstrim trigger.
 In addition, issue_discard_thread is calling too much due to the number of
 discard commands remaining in the pending list. I added a timer to control
 it likewise gc_thread.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 Documentation/ABI/testing/sysfs-fs-f2fs |  9 ++++
 fs/f2fs/f2fs.h                          | 12 +++++
 fs/f2fs/segment.c                       | 91 ++++++++++++++++++++++++++++-----
 fs/f2fs/sysfs.c                         | 23 +++++++++
 4 files changed, 121 insertions(+), 14 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 621da3fc56c5..11b7f4ebea7c 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -57,6 +57,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
 Description:
 		 Controls the issue rate of small discard commands.
 
+What:          /sys/fs/f2fs/<disk>/discard_granularity
+Date:          July 2017
+Contact:       "Chao Yu" <yuchao0@huawei.com>
+Description:
+		Controls discard granularity of inner discard thread, inner thread
+		will not issue discards with size that is smaller than granularity.
+		The unit size is one block, now only support configuring in range
+		of [1, 512].
+
 What:		/sys/fs/f2fs/<disk>/max_victim_search
 Date:		January 2014
 Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e252e5bf9791..4b993961d81d 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -148,6 +148,8 @@ enum {
 		(BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
 #define MAX_DISCARD_BLOCKS(sbi)		BLKS_PER_SEC(sbi)
 #define DISCARD_ISSUE_RATE		8
+#define DEF_MIN_DISCARD_ISSUE_TIME	50	/* 50 ms, if exists */
+#define DEF_MAX_DISCARD_ISSUE_TIME	60000	/* 60 s, if no candidates */
 #define DEF_CP_INTERVAL			60	/* 60 secs */
 #define DEF_IDLE_INTERVAL		5	/* 5 secs */
 
@@ -196,11 +198,18 @@ struct discard_entry {
 	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
 };
 
+/* default discard granularity of inner discard thread, unit: block count */
+#define DEFAULT_DISCARD_GRANULARITY		16
+
 /* max discard pend list number */
 #define MAX_PLIST_NUM		512
 #define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
 					(MAX_PLIST_NUM - 1) : (blk_num - 1))
 
+#define P_ACTIVE	0x01
+#define P_TRIM		0x02
+#define plist_issue(tag)	(((tag) & P_ACTIVE) || ((tag) & P_TRIM))
+
 enum {
 	D_PREP,
 	D_SUBMIT,
@@ -236,11 +245,14 @@ struct discard_cmd_control {
 	struct task_struct *f2fs_issue_discard;	/* discard thread */
 	struct list_head entry_list;		/* 4KB discard entry list */
 	struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
+	unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
 	struct list_head wait_list;		/* store on-flushing entries */
 	wait_queue_head_t discard_wait_queue;	/* waiting queue for wake-up */
+	unsigned int discard_wake;		/* to wake up discard thread */
 	struct mutex cmd_lock;
 	unsigned int nr_discards;		/* # of discards in the list */
 	unsigned int max_discards;		/* max. discards to be issued */
+	unsigned int discard_granularity;	/* discard granularity */
 	unsigned int undiscard_blks;		/* # of undiscard blocks */
 	atomic_t issued_discard;		/* # of issued discard */
 	atomic_t issing_discard;		/* # of issing discard */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 05144b3a7f62..1387925a0d83 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1016,32 +1016,65 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
 	return 0;
 }
 
-static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
+static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
 {
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 	struct list_head *pend_list;
 	struct discard_cmd *dc, *tmp;
 	struct blk_plug plug;
-	int i, iter = 0;
+	int iter = 0, issued = 0;
+	int i;
 
 	mutex_lock(&dcc->cmd_lock);
 	f2fs_bug_on(sbi,
 		!__check_rb_tree_consistence(sbi, &dcc->root));
 	blk_start_plug(&plug);
-	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+	for (i = MAX_PLIST_NUM - 1;
+			i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
 		pend_list = &dcc->pend_list[i];
 		list_for_each_entry_safe(dc, tmp, pend_list, list) {
 			f2fs_bug_on(sbi, dc->state != D_PREP);
 
-			if (!issue_cond || is_idle(sbi))
+			/* Hurry up to finish fstrim */
+			if (dcc->pend_list_tag[i] & P_TRIM) {
+				__submit_discard_cmd(sbi, dc);
+				issued++;
+				continue;
+			}
+
+			if (!issue_cond || is_idle(sbi)) {
+				issued++;
 				__submit_discard_cmd(sbi, dc);
+			}
 			if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
 				goto out;
 		}
+		if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
+			dcc->pend_list_tag[i] &= (~P_TRIM);
 	}
 out:
 	blk_finish_plug(&plug);
 	mutex_unlock(&dcc->cmd_lock);
+
+	return issued;
+}
+
+static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
+{
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	struct list_head *pend_list;
+	struct discard_cmd *dc, *tmp;
+	int i;
+
+	mutex_lock(&dcc->cmd_lock);
+	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
+		pend_list = &dcc->pend_list[i];
+		list_for_each_entry_safe(dc, tmp, pend_list, list) {
+			f2fs_bug_on(sbi, dc->state != D_PREP);
+			__remove_discard_cmd(sbi, dc);
+		}
+	}
+	mutex_unlock(&dcc->cmd_lock);
 }
 
 static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
@@ -1126,34 +1159,56 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
 void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
 {
 	__issue_discard_cmd(sbi, false);
+	__drop_discard_cmd(sbi);
 	__wait_discard_cmd(sbi, false);
 }
 
+static void mark_discard_range_all(struct f2fs_sb_info *sbi)
+{
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	int i;
+
+	mutex_lock(&dcc->cmd_lock);
+	for (i = 0; i < MAX_PLIST_NUM; i++)
+		dcc->pend_list_tag[i] |= P_TRIM;
+	mutex_unlock(&dcc->cmd_lock);
+}
+
 static int issue_discard_thread(void *data)
 {
 	struct f2fs_sb_info *sbi = data;
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 	wait_queue_head_t *q = &dcc->discard_wait_queue;
+	unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
+	int issued;
 
 	set_freezable();
 
 	do {
-		wait_event_interruptible(*q, kthread_should_stop() ||
-					freezing(current) ||
-					atomic_read(&dcc->discard_cmd_cnt));
+		wait_event_interruptible_timeout(*q,
+				kthread_should_stop() || freezing(current) ||
+				dcc->discard_wake,
+				msecs_to_jiffies(wait_ms));
 		if (try_to_freeze())
 			continue;
 		if (kthread_should_stop())
 			return 0;
 
+		if (dcc->discard_wake)
+			dcc->discard_wake = 0;
+
 		sb_start_intwrite(sbi->sb);
 
-		__issue_discard_cmd(sbi, true);
-		__wait_discard_cmd(sbi, true);
+		issued = __issue_discard_cmd(sbi, true);
+		if (issued) {
+			__wait_discard_cmd(sbi, true);
+			wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
+		} else {
+			wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
+		}
 
 		sb_end_intwrite(sbi->sb);
 
-		congestion_wait(BLK_RW_SYNC, HZ/50);
 	} while (!kthread_should_stop());
 	return 0;
 }
@@ -1344,7 +1399,8 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
 
 void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 {
-	struct list_head *head = &(SM_I(sbi)->dcc_info->entry_list);
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	struct list_head *head = &dcc->entry_list;
 	struct discard_entry *entry, *this;
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
@@ -1426,11 +1482,12 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 			goto find_next;
 
 		list_del(&entry->list);
-		SM_I(sbi)->dcc_info->nr_discards -= total_len;
+		dcc->nr_discards -= total_len;
 		kmem_cache_free(discard_entry_slab, entry);
 	}
 
-	wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
+	dcc->discard_wake = 1;
+	wake_up_interruptible_all(&dcc->discard_wait_queue);
 }
 
 static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
@@ -1448,9 +1505,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 	if (!dcc)
 		return -ENOMEM;
 
+	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
 	INIT_LIST_HEAD(&dcc->entry_list);
-	for (i = 0; i < MAX_PLIST_NUM; i++)
+	for (i = 0; i < MAX_PLIST_NUM; i++) {
 		INIT_LIST_HEAD(&dcc->pend_list[i]);
+		if (i >= dcc->discard_granularity - 1)
+			dcc->pend_list_tag[i] |= P_ACTIVE;
+	}
 	INIT_LIST_HEAD(&dcc->wait_list);
 	mutex_init(&dcc->cmd_lock);
 	atomic_set(&dcc->issued_discard, 0);
@@ -2127,6 +2188,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 
 		schedule();
 	}
+	/* It's time to issue all the filed discards */
+	mark_discard_range_all(sbi);
 out:
 	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
 	return err;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index c40e5d24df9f..4bcaa9059026 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 		spin_unlock(&sbi->stat_lock);
 		return count;
 	}
+
+	if (!strcmp(a->attr.name, "discard_granularity")) {
+		struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+		int i;
+
+		if (t == 0 || t > MAX_PLIST_NUM)
+			return -EINVAL;
+		if (t == *ui)
+			return count;
+
+		mutex_lock(&dcc->cmd_lock);
+		for (i = 0; i < MAX_PLIST_NUM; i++) {
+			if (i >= t - 1)
+				dcc->pend_list_tag[i] |= P_ACTIVE;
+			else
+				dcc->pend_list_tag[i] &= (~P_ACTIVE);
+		}
+		mutex_unlock(&dcc->cmd_lock);
+		return count;
+	}
+
 	*ui = t;
 
 	if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
@@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
+F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
 F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
@@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(gc_urgent),
 	ATTR_LIST(reclaim_segments),
 	ATTR_LIST(max_small_discards),
+	ATTR_LIST(discard_granularity),
 	ATTR_LIST(batched_trim_sections),
 	ATTR_LIST(ipu_policy),
 	ATTR_LIST(min_ipu_util),
-- 
2.14.0.rc1.383.gd1ce394fe2-goog

Re: [f2fs-dev] [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Ju Hyung Park]

When 'fstrim' is called for manual trim, a BUG() can be triggered
randomly with this patch.

I'm seeing this issue on both x86 Desktop and arm64 Android phone.

On x86 Desktop, this was caused during Ubuntu boot-up. I have a
cronjob installed
which calls 'fstrim -v /' during boot.
On arm64 Android, this was caused during GC looping with
1ms gc_min_sleep_time & gc_max_sleep_time.

Thanks.

[26671.666421] ------------[ cut here ]------------
[26671.666426] WARNING: CPU: 8 PID: 103479 at fs/f2fs/segment.c:797
__remove_discard_cmd+0xb9/0xd0
[26671.666427] Modules linked in: ftdi_sio usbserial uas usb_storage
vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
snd_seq_device
[26671.666450]  snd_timer snd soundcore k10temp i2c_piix4
nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
async_pq async_xor async_tx raid1 multipath linear hid_generic
hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
[26671.666471] CPU: 8 PID: 103479 Comm: fstrim Tainted: P           O
  4.13.4-zen+ #1
[26671.666472] Hardware name: System manufacturer System Product
Name/PRIME X399-A, BIOS 0318 08/11/2017
[26671.666472] task: ffff8804ad535800 task.stack: ffff88047ee38000
[26671.666474] RIP: 0010:__remove_discard_cmd+0xb9/0xd0
[26671.666474] RSP: 0018:ffff88047ee3bd00 EFLAGS: 00010202
[26671.666475] RAX: ffff88081801a500 RBX: ffff88047eeaed00 RCX: ffff88047eeaedf8
[26671.666475] RDX: 0000000000000001 RSI: ffff88047eeaed00 RDI: ffff880802555800
[26671.666476] RBP: ffff8808134d0000 R08: ffff8804ad535800 R09: 0000000000000001
[26671.666476] R10: ffff88047ee3bd18 R11: 0000000000000000 R12: ffff880802555800
[26671.666476] R13: 0000000000000000 R14: ffff88047eeaedd0 R15: ffff8808134d0000
[26671.666477] FS:  00007f44cddad2c0(0000) GS:ffff88081ca00000(0000)
knlGS:0000000000000000
[26671.666478] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[26671.666478] CR2: 00007f88f5776328 CR3: 000000058ce4a000 CR4: 00000000003406e0
[26671.666479] Call Trace:
[26671.666481]  ? __wait_discard_cmd+0x7a/0xc0
[26671.666482]  ? f2fs_trim_fs+0x1c1/0x210
[26671.666484]  ? f2fs_ioctl+0x75a/0x2320
[26671.666486]  ? do_filp_open+0x99/0xe0
[26671.666487]  ? cp_new_stat+0x138/0x150
[26671.666489]  ? do_vfs_ioctl+0x88/0x5c0
[26671.666490]  ? SyS_newfstat+0x29/0x40
[26671.666491]  ? SyS_ioctl+0x6f/0x80
[26671.666493]  ? entry_SYSCALL_64_fastpath+0x1e/0xa9
[26671.666493] Code: 48 89 de 8b 43 1c 48 8b 3d 4d 8c 31 01 29 85 74
22 00 00 e8 fa 01 d5 ff f0 ff 8d 80 22 00 00 5b 5d c3 c7 43 64 00 00
00 00 eb 92 <0f> ff f0 80 4f 20 04 e9 53 ff ff ff 90 66 2e 0f 1f 84 00
00 00
[26671.666506] ---[ end trace 613553f7a4728b5a ]---
[26672.553742] general protection fault: 0000 [#1] PREEMPT SMP
[26672.553746] Modules linked in: ftdi_sio usbserial uas usb_storage
vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
snd_seq_device
[26672.553771]  snd_timer snd soundcore k10temp i2c_piix4
nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
async_pq async_xor async_tx raid1 multipath linear hid_generic
hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
[26672.553792] CPU: 10 PID: 1287 Comm: f2fs_discard-25 Tainted: P
  W  O    4.13.4-zen+ #1
[26672.553793] Hardware name: System manufacturer System Product
Name/PRIME X399-A, BIOS 0318 08/11/2017
[26672.553794] task: ffff8808159c1600 task.stack: ffff880813304000
[26672.553798] RIP: 0010:__remove_discard_cmd+0x6a/0xd0
[26672.553799] RSP: 0018:ffff880813307e20 EFLAGS: 00010296
[26672.553800] RAX: dead000000000200 RBX: ffff88047eeaed00 RCX: ffff8808159c1601
[26672.553801] RDX: dead000000000100 RSI: ffff8808134d2288 RDI: ffff88047eeaed00
[26672.553801] RBP: ffff8808134d0000 R08: 0000184230172c00 R09: 0000000000000006
[26672.553802] R10: ffff880813307e38 R11: 0000000000000023 R12: ffff880802555800
[26672.553803] R13: 0000000000000001 R14: ffff88047eeaed00 R15: ffff8808134d0000
[26672.553804] FS:  0000000000000000(0000) GS:ffff88081ca80000(0000)
knlGS:0000000000000000
[26672.553805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[26672.553805] CR2: 00007f88f2f71328 CR3: 000000048be79000 CR4: 00000000003406e0
[26672.553806] Call Trace:
[26672.553808]  ? __wait_one_discard_bio+0x41/0x60
[26672.553809]  ? __wait_discard_cmd+0xbb/0xc0
[26672.553811]  ? issue_discard_thread+0x196/0x200
[26672.553813]  ? wait_woken+0x80/0x80
[26672.553814]  ? mark_discard_range_all.isra.11+0x40/0x40
[26672.553816]  ? kthread+0x112/0x130
[26672.553817]  ? kthread_create_on_node+0x40/0x40
[26672.553818]  ? do_group_exit+0x2e/0xa0
[26672.553820]  ? ret_from_fork+0x25/0x30
[26672.553821] Code: 8b 43 20 48 8b 3f e8 56 6c fe ff 58 80 7b 62 02
75 07 f0 ff 8d 7c 22 00 00 48 8b 53 28 48 8b 43 30 48 8d b5 88 22 00
00 48 89 df <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89
43 28
[26672.553835] RIP: __remove_discard_cmd+0x6a/0xd0 RSP: ffff880813307e20
[26672.553836] ---[ end trace 613553f7a4728b5b ]---

On Tue, Aug 22, 2017 at 5:42 AM, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
> On 08/18, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> Sorry for the delay, the modification looks good to me. ;)
>
> We must avoid waking up discard thread caused by # of pending commands
> which are never issued.
>
> From a73f8807248c2f42328a2204eab16a3b8d32c83e Mon Sep 17 00:00:00 2001
> From: Chao Yu <yuchao0@huawei.com>
> Date: Mon, 7 Aug 2017 23:09:56 +0800
> Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry
>
> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
> f2fs to issue 4K size discard in real-time discard mode. However, issuing
> smaller discard may cost more lifetime but releasing less free space in
> flash device. Since f2fs has ability of separating hot/cold data and
> garbage collection, we can expect that small-sized invalid region would
> expand soon with OPU, deletion or garbage collection on valid datas, so
> it's better to delay or skip issuing smaller size discards, it could help
> to reduce overmuch consumption of IO bandwidth and lifetime of flash
> storage.
>
> This patch makes f2fs selectng 64K size as its default minimal
> granularity, and issue discard with the size which is not smaller than
> minimal granularity. Also it exposes discard granularity as sysfs entry
> for configuration in different scenario.
>
> Jaegeuk Kim:
>  We must issue all the accumulated discard commands when fstrim is called.
>  So, I've added pend_list_tag[] to indicate whether we should issue the
>  commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
>  P_TRIM is set once at a time, given fstrim trigger.
>  In addition, issue_discard_thread is calling too much due to the number of
>  discard commands remaining in the pending list. I added a timer to control
>  it likewise gc_thread.
>
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 ++++
>  fs/f2fs/f2fs.h                          | 12 +++++
>  fs/f2fs/segment.c                       | 91 ++++++++++++++++++++++++++++-----
>  fs/f2fs/sysfs.c                         | 23 +++++++++
>  4 files changed, 121 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 621da3fc56c5..11b7f4ebea7c 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -57,6 +57,15 @@ Contact:     "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>  Description:
>                  Controls the issue rate of small discard commands.
>
> +What:          /sys/fs/f2fs/<disk>/discard_granularity
> +Date:          July 2017
> +Contact:       "Chao Yu" <yuchao0@huawei.com>
> +Description:
> +               Controls discard granularity of inner discard thread, inner thread
> +               will not issue discards with size that is smaller than granularity.
> +               The unit size is one block, now only support configuring in range
> +               of [1, 512].
> +
>  What:          /sys/fs/f2fs/<disk>/max_victim_search
>  Date:          January 2014
>  Contact:       "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e252e5bf9791..4b993961d81d 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -148,6 +148,8 @@ enum {
>                 (BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
>  #define MAX_DISCARD_BLOCKS(sbi)                BLKS_PER_SEC(sbi)
>  #define DISCARD_ISSUE_RATE             8
> +#define DEF_MIN_DISCARD_ISSUE_TIME     50      /* 50 ms, if exists */
> +#define DEF_MAX_DISCARD_ISSUE_TIME     60000   /* 60 s, if no candidates */
>  #define DEF_CP_INTERVAL                        60      /* 60 secs */
>  #define DEF_IDLE_INTERVAL              5       /* 5 secs */
>
> @@ -196,11 +198,18 @@ struct discard_entry {
>         unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard bitmap */
>  };
>
> +/* default discard granularity of inner discard thread, unit: block count */
> +#define DEFAULT_DISCARD_GRANULARITY            16
> +
>  /* max discard pend list number */
>  #define MAX_PLIST_NUM          512
>  #define plist_idx(blk_num)     ((blk_num) >= MAX_PLIST_NUM ?           \
>                                         (MAX_PLIST_NUM - 1) : (blk_num - 1))
>
> +#define P_ACTIVE       0x01
> +#define P_TRIM         0x02
> +#define plist_issue(tag)       (((tag) & P_ACTIVE) || ((tag) & P_TRIM))
> +
>  enum {
>         D_PREP,
>         D_SUBMIT,
> @@ -236,11 +245,14 @@ struct discard_cmd_control {
>         struct task_struct *f2fs_issue_discard; /* discard thread */
>         struct list_head entry_list;            /* 4KB discard entry list */
>         struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
> +       unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
>         struct list_head wait_list;             /* store on-flushing entries */
>         wait_queue_head_t discard_wait_queue;   /* waiting queue for wake-up */
> +       unsigned int discard_wake;              /* to wake up discard thread */
>         struct mutex cmd_lock;
>         unsigned int nr_discards;               /* # of discards in the list */
>         unsigned int max_discards;              /* max. discards to be issued */
> +       unsigned int discard_granularity;       /* discard granularity */
>         unsigned int undiscard_blks;            /* # of undiscard blocks */
>         atomic_t issued_discard;                /* # of issued discard */
>         atomic_t issing_discard;                /* # of issing discard */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 05144b3a7f62..1387925a0d83 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1016,32 +1016,65 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
>         return 0;
>  }
>
> -static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
> +static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>  {
>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>         struct list_head *pend_list;
>         struct discard_cmd *dc, *tmp;
>         struct blk_plug plug;
> -       int i, iter = 0;
> +       int iter = 0, issued = 0;
> +       int i;
>
>         mutex_lock(&dcc->cmd_lock);
>         f2fs_bug_on(sbi,
>                 !__check_rb_tree_consistence(sbi, &dcc->root));
>         blk_start_plug(&plug);
> -       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> +       for (i = MAX_PLIST_NUM - 1;
> +                       i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
>                 pend_list = &dcc->pend_list[i];
>                 list_for_each_entry_safe(dc, tmp, pend_list, list) {
>                         f2fs_bug_on(sbi, dc->state != D_PREP);
>
> -                       if (!issue_cond || is_idle(sbi))
> +                       /* Hurry up to finish fstrim */
> +                       if (dcc->pend_list_tag[i] & P_TRIM) {
> +                               __submit_discard_cmd(sbi, dc);
> +                               issued++;
> +                               continue;
> +                       }
> +
> +                       if (!issue_cond || is_idle(sbi)) {
> +                               issued++;
>                                 __submit_discard_cmd(sbi, dc);
> +                       }
>                         if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
>                                 goto out;
>                 }
> +               if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
> +                       dcc->pend_list_tag[i] &= (~P_TRIM);
>         }
>  out:
>         blk_finish_plug(&plug);
>         mutex_unlock(&dcc->cmd_lock);
> +
> +       return issued;
> +}
> +
> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
> +{
> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +       struct list_head *pend_list;
> +       struct discard_cmd *dc, *tmp;
> +       int i;
> +
> +       mutex_lock(&dcc->cmd_lock);
> +       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> +               pend_list = &dcc->pend_list[i];
> +               list_for_each_entry_safe(dc, tmp, pend_list, list) {
> +                       f2fs_bug_on(sbi, dc->state != D_PREP);
> +                       __remove_discard_cmd(sbi, dc);
> +               }
> +       }
> +       mutex_unlock(&dcc->cmd_lock);
>  }
>
>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
> @@ -1126,34 +1159,56 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>  {
>         __issue_discard_cmd(sbi, false);
> +       __drop_discard_cmd(sbi);
>         __wait_discard_cmd(sbi, false);
>  }
>
> +static void mark_discard_range_all(struct f2fs_sb_info *sbi)
> +{
> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +       int i;
> +
> +       mutex_lock(&dcc->cmd_lock);
> +       for (i = 0; i < MAX_PLIST_NUM; i++)
> +               dcc->pend_list_tag[i] |= P_TRIM;
> +       mutex_unlock(&dcc->cmd_lock);
> +}
> +
>  static int issue_discard_thread(void *data)
>  {
>         struct f2fs_sb_info *sbi = data;
>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>         wait_queue_head_t *q = &dcc->discard_wait_queue;
> +       unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
> +       int issued;
>
>         set_freezable();
>
>         do {
> -               wait_event_interruptible(*q, kthread_should_stop() ||
> -                                       freezing(current) ||
> -                                       atomic_read(&dcc->discard_cmd_cnt));
> +               wait_event_interruptible_timeout(*q,
> +                               kthread_should_stop() || freezing(current) ||
> +                               dcc->discard_wake,
> +                               msecs_to_jiffies(wait_ms));
>                 if (try_to_freeze())
>                         continue;
>                 if (kthread_should_stop())
>                         return 0;
>
> +               if (dcc->discard_wake)
> +                       dcc->discard_wake = 0;
> +
>                 sb_start_intwrite(sbi->sb);
>
> -               __issue_discard_cmd(sbi, true);
> -               __wait_discard_cmd(sbi, true);
> +               issued = __issue_discard_cmd(sbi, true);
> +               if (issued) {
> +                       __wait_discard_cmd(sbi, true);
> +                       wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
> +               } else {
> +                       wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
> +               }
>
>                 sb_end_intwrite(sbi->sb);
>
> -               congestion_wait(BLK_RW_SYNC, HZ/50);
>         } while (!kthread_should_stop());
>         return 0;
>  }
> @@ -1344,7 +1399,8 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
>
>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  {
> -       struct list_head *head = &(SM_I(sbi)->dcc_info->entry_list);
> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +       struct list_head *head = &dcc->entry_list;
>         struct discard_entry *entry, *this;
>         struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
>         unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
> @@ -1426,11 +1482,12 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>                         goto find_next;
>
>                 list_del(&entry->list);
> -               SM_I(sbi)->dcc_info->nr_discards -= total_len;
> +               dcc->nr_discards -= total_len;
>                 kmem_cache_free(discard_entry_slab, entry);
>         }
>
> -       wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
> +       dcc->discard_wake = 1;
> +       wake_up_interruptible_all(&dcc->discard_wait_queue);
>  }
>
>  static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
> @@ -1448,9 +1505,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>         if (!dcc)
>                 return -ENOMEM;
>
> +       dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>         INIT_LIST_HEAD(&dcc->entry_list);
> -       for (i = 0; i < MAX_PLIST_NUM; i++)
> +       for (i = 0; i < MAX_PLIST_NUM; i++) {
>                 INIT_LIST_HEAD(&dcc->pend_list[i]);
> +               if (i >= dcc->discard_granularity - 1)
> +                       dcc->pend_list_tag[i] |= P_ACTIVE;
> +       }
>         INIT_LIST_HEAD(&dcc->wait_list);
>         mutex_init(&dcc->cmd_lock);
>         atomic_set(&dcc->issued_discard, 0);
> @@ -2127,6 +2188,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>
>                 schedule();
>         }
> +       /* It's time to issue all the filed discards */
> +       mark_discard_range_all(sbi);
>  out:
>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>         return err;
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index c40e5d24df9f..4bcaa9059026 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>                 spin_unlock(&sbi->stat_lock);
>                 return count;
>         }
> +
> +       if (!strcmp(a->attr.name, "discard_granularity")) {
> +               struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +               int i;
> +
> +               if (t == 0 || t > MAX_PLIST_NUM)
> +                       return -EINVAL;
> +               if (t == *ui)
> +                       return count;
> +
> +               mutex_lock(&dcc->cmd_lock);
> +               for (i = 0; i < MAX_PLIST_NUM; i++) {
> +                       if (i >= t - 1)
> +                               dcc->pend_list_tag[i] |= P_ACTIVE;
> +                       else
> +                               dcc->pend_list_tag[i] &= (~P_ACTIVE);
> +               }
> +               mutex_unlock(&dcc->cmd_lock);
> +               return count;
> +       }
> +
>         *ui = t;
>
>         if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
> @@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
> @@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
>         ATTR_LIST(gc_urgent),
>         ATTR_LIST(reclaim_segments),
>         ATTR_LIST(max_small_discards),
> +       ATTR_LIST(discard_granularity),
>         ATTR_LIST(batched_trim_sections),
>         ATTR_LIST(ipu_policy),
>         ATTR_LIST(min_ipu_util),
> --
> 2.14.0.rc1.383.gd1ce394fe2-goog
>
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
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> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [f2fs-dev] [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Chao Yu]

Hi Park,

Thanks for the report, could have a try with below patch:

>From 5fa30e8cdcb93f210e25142c48a884be383c6121 Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@huawei.com>
Date: Mon, 2 Oct 2017 02:50:16 +0800
Subject: [PATCH] f2fs: fix potential panic during fstrim

As Ju Hyung Park reported:

"When 'fstrim' is called for manual trim, a BUG() can be triggered
randomly with this patch.

I'm seeing this issue on both x86 Desktop and arm64 Android phone.

On x86 Desktop, this was caused during Ubuntu boot-up. I have a
cronjob installed which calls 'fstrim -v /' during boot. On arm64
Android, this was caused during GC looping with 1ms gc_min_sleep_time
& gc_max_sleep_time."

Root cause of this issue is that f2fs_wait_discard_bios can only be
used by f2fs_put_super, because during put_super there must be no
other referrers, so it can ignore discard entry's reference count
when removing the entry, otherwise in other caller we will hit bug_on
in __remove_discard_cmd as there may be other issuer added reference
count in discard entry.

Thread A				Thread B
					- issue_discard_thread
- f2fs_ioc_fitrim
 - f2fs_trim_fs
  - f2fs_wait_discard_bios
   - __issue_discard_cmd
    - __submit_discard_cmd
					 - __wait_discard_cmd
					  - dc->ref++
					  - __wait_one_discard_bio
   - __wait_discard_cmd
    - __remove_discard_cmd
     - f2fs_bug_on(sbi, dc->ref)

Fixes: 969d1b180d987c2be02de890d0fff0f66a0e80de
Reported-by: Ju Hyung Park <qkrwngud825@gmail.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
 fs/f2fs/f2fs.h    | 2 +-
 fs/f2fs/segment.c | 6 +++---
 fs/f2fs/super.c   | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9a7c90386947..4b4a72f392be 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2525,7 +2525,7 @@ void invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr);
 bool is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
 void refresh_sit_entry(struct f2fs_sb_info *sbi, block_t old, block_t new);
 void stop_discard_thread(struct f2fs_sb_info *sbi);
-void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi);
+void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount);
 void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc);
 void release_discard_addrs(struct f2fs_sb_info *sbi);
 int npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index dedf0209d820..e28245b7e44e 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1210,11 +1210,11 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
 }

 /* This comes from f2fs_put_super and f2fs_trim_fs */
-void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
+void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount)
 {
 	__issue_discard_cmd(sbi, false);
 	__drop_discard_cmd(sbi);
-	__wait_discard_cmd(sbi, false);
+	__wait_discard_cmd(sbi, !umount);
 }

 static void mark_discard_range_all(struct f2fs_sb_info *sbi)
@@ -2244,7 +2244,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
 	}
 	/* It's time to issue all the filed discards */
 	mark_discard_range_all(sbi);
-	f2fs_wait_discard_bios(sbi);
+	f2fs_wait_discard_bios(sbi, false);
 out:
 	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
 	return err;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 89f61eb3d167..933c3d529e65 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -801,7 +801,7 @@ static void f2fs_put_super(struct super_block *sb)
 	}

 	/* be sure to wait for any on-going discard commands */
-	f2fs_wait_discard_bios(sbi);
+	f2fs_wait_discard_bios(sbi, true);

 	if (f2fs_discard_en(sbi) && !sbi->discard_blks) {
 		struct cp_control cpc = {
-- 
2.14.1.145.gb3622a4ee

On 2017/10/2 3:29, Ju Hyung Park wrote:
> When 'fstrim' is called for manual trim, a BUG() can be triggered
> randomly with this patch.
> 
> I'm seeing this issue on both x86 Desktop and arm64 Android phone.
> 
> On x86 Desktop, this was caused during Ubuntu boot-up. I have a
> cronjob installed
> which calls 'fstrim -v /' during boot.
> On arm64 Android, this was caused during GC looping with
> 1ms gc_min_sleep_time & gc_max_sleep_time.
> 
> Thanks.
> 
> [26671.666421] ------------[ cut here ]------------
> [26671.666426] WARNING: CPU: 8 PID: 103479 at fs/f2fs/segment.c:797
> __remove_discard_cmd+0xb9/0xd0
> [26671.666427] Modules linked in: ftdi_sio usbserial uas usb_storage
> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
> snd_seq_device
> [26671.666450]  snd_timer snd soundcore k10temp i2c_piix4
> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
> async_pq async_xor async_tx raid1 multipath linear hid_generic
> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
> [26671.666471] CPU: 8 PID: 103479 Comm: fstrim Tainted: P           O
>   4.13.4-zen+ #1
> [26671.666472] Hardware name: System manufacturer System Product
> Name/PRIME X399-A, BIOS 0318 08/11/2017
> [26671.666472] task: ffff8804ad535800 task.stack: ffff88047ee38000
> [26671.666474] RIP: 0010:__remove_discard_cmd+0xb9/0xd0
> [26671.666474] RSP: 0018:ffff88047ee3bd00 EFLAGS: 00010202
> [26671.666475] RAX: ffff88081801a500 RBX: ffff88047eeaed00 RCX: ffff88047eeaedf8
> [26671.666475] RDX: 0000000000000001 RSI: ffff88047eeaed00 RDI: ffff880802555800
> [26671.666476] RBP: ffff8808134d0000 R08: ffff8804ad535800 R09: 0000000000000001
> [26671.666476] R10: ffff88047ee3bd18 R11: 0000000000000000 R12: ffff880802555800
> [26671.666476] R13: 0000000000000000 R14: ffff88047eeaedd0 R15: ffff8808134d0000
> [26671.666477] FS:  00007f44cddad2c0(0000) GS:ffff88081ca00000(0000)
> knlGS:0000000000000000
> [26671.666478] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [26671.666478] CR2: 00007f88f5776328 CR3: 000000058ce4a000 CR4: 00000000003406e0
> [26671.666479] Call Trace:
> [26671.666481]  ? __wait_discard_cmd+0x7a/0xc0
> [26671.666482]  ? f2fs_trim_fs+0x1c1/0x210
> [26671.666484]  ? f2fs_ioctl+0x75a/0x2320
> [26671.666486]  ? do_filp_open+0x99/0xe0
> [26671.666487]  ? cp_new_stat+0x138/0x150
> [26671.666489]  ? do_vfs_ioctl+0x88/0x5c0
> [26671.666490]  ? SyS_newfstat+0x29/0x40
> [26671.666491]  ? SyS_ioctl+0x6f/0x80
> [26671.666493]  ? entry_SYSCALL_64_fastpath+0x1e/0xa9
> [26671.666493] Code: 48 89 de 8b 43 1c 48 8b 3d 4d 8c 31 01 29 85 74
> 22 00 00 e8 fa 01 d5 ff f0 ff 8d 80 22 00 00 5b 5d c3 c7 43 64 00 00
> 00 00 eb 92 <0f> ff f0 80 4f 20 04 e9 53 ff ff ff 90 66 2e 0f 1f 84 00
> 00 00
> [26671.666506] ---[ end trace 613553f7a4728b5a ]---
> [26672.553742] general protection fault: 0000 [#1] PREEMPT SMP
> [26672.553746] Modules linked in: ftdi_sio usbserial uas usb_storage
> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
> snd_seq_device
> [26672.553771]  snd_timer snd soundcore k10temp i2c_piix4
> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
> async_pq async_xor async_tx raid1 multipath linear hid_generic
> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
> [26672.553792] CPU: 10 PID: 1287 Comm: f2fs_discard-25 Tainted: P
>   W  O    4.13.4-zen+ #1
> [26672.553793] Hardware name: System manufacturer System Product
> Name/PRIME X399-A, BIOS 0318 08/11/2017
> [26672.553794] task: ffff8808159c1600 task.stack: ffff880813304000
> [26672.553798] RIP: 0010:__remove_discard_cmd+0x6a/0xd0
> [26672.553799] RSP: 0018:ffff880813307e20 EFLAGS: 00010296
> [26672.553800] RAX: dead000000000200 RBX: ffff88047eeaed00 RCX: ffff8808159c1601
> [26672.553801] RDX: dead000000000100 RSI: ffff8808134d2288 RDI: ffff88047eeaed00
> [26672.553801] RBP: ffff8808134d0000 R08: 0000184230172c00 R09: 0000000000000006
> [26672.553802] R10: ffff880813307e38 R11: 0000000000000023 R12: ffff880802555800
> [26672.553803] R13: 0000000000000001 R14: ffff88047eeaed00 R15: ffff8808134d0000
> [26672.553804] FS:  0000000000000000(0000) GS:ffff88081ca80000(0000)
> knlGS:0000000000000000
> [26672.553805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [26672.553805] CR2: 00007f88f2f71328 CR3: 000000048be79000 CR4: 00000000003406e0
> [26672.553806] Call Trace:
> [26672.553808]  ? __wait_one_discard_bio+0x41/0x60
> [26672.553809]  ? __wait_discard_cmd+0xbb/0xc0
> [26672.553811]  ? issue_discard_thread+0x196/0x200
> [26672.553813]  ? wait_woken+0x80/0x80
> [26672.553814]  ? mark_discard_range_all.isra.11+0x40/0x40
> [26672.553816]  ? kthread+0x112/0x130
> [26672.553817]  ? kthread_create_on_node+0x40/0x40
> [26672.553818]  ? do_group_exit+0x2e/0xa0
> [26672.553820]  ? ret_from_fork+0x25/0x30
> [26672.553821] Code: 8b 43 20 48 8b 3f e8 56 6c fe ff 58 80 7b 62 02
> 75 07 f0 ff 8d 7c 22 00 00 48 8b 53 28 48 8b 43 30 48 8d b5 88 22 00
> 00 48 89 df <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89
> 43 28
> [26672.553835] RIP: __remove_discard_cmd+0x6a/0xd0 RSP: ffff880813307e20
> [26672.553836] ---[ end trace 613553f7a4728b5b ]---
> 
> On Tue, Aug 22, 2017 at 5:42 AM, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
>> On 08/18, Chao Yu wrote:
>>> Hi Jaegeuk,
>>>
>>> Sorry for the delay, the modification looks good to me. ;)
>>
>> We must avoid waking up discard thread caused by # of pending commands
>> which are never issued.
>>
>> From a73f8807248c2f42328a2204eab16a3b8d32c83e Mon Sep 17 00:00:00 2001
>> From: Chao Yu <yuchao0@huawei.com>
>> Date: Mon, 7 Aug 2017 23:09:56 +0800
>> Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry
>>
>> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
>> f2fs to issue 4K size discard in real-time discard mode. However, issuing
>> smaller discard may cost more lifetime but releasing less free space in
>> flash device. Since f2fs has ability of separating hot/cold data and
>> garbage collection, we can expect that small-sized invalid region would
>> expand soon with OPU, deletion or garbage collection on valid datas, so
>> it's better to delay or skip issuing smaller size discards, it could help
>> to reduce overmuch consumption of IO bandwidth and lifetime of flash
>> storage.
>>
>> This patch makes f2fs selectng 64K size as its default minimal
>> granularity, and issue discard with the size which is not smaller than
>> minimal granularity. Also it exposes discard granularity as sysfs entry
>> for configuration in different scenario.
>>
>> Jaegeuk Kim:
>>  We must issue all the accumulated discard commands when fstrim is called.
>>  So, I've added pend_list_tag[] to indicate whether we should issue the
>>  commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
>>  P_TRIM is set once at a time, given fstrim trigger.
>>  In addition, issue_discard_thread is calling too much due to the number of
>>  discard commands remaining in the pending list. I added a timer to control
>>  it likewise gc_thread.
>>
>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>> ---
>>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 ++++
>>  fs/f2fs/f2fs.h                          | 12 +++++
>>  fs/f2fs/segment.c                       | 91 ++++++++++++++++++++++++++++-----
>>  fs/f2fs/sysfs.c                         | 23 +++++++++
>>  4 files changed, 121 insertions(+), 14 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>> index 621da3fc56c5..11b7f4ebea7c 100644
>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>> @@ -57,6 +57,15 @@ Contact:     "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>>  Description:
>>                  Controls the issue rate of small discard commands.
>>
>> +What:          /sys/fs/f2fs/<disk>/discard_granularity
>> +Date:          July 2017
>> +Contact:       "Chao Yu" <yuchao0@huawei.com>
>> +Description:
>> +               Controls discard granularity of inner discard thread, inner thread
>> +               will not issue discards with size that is smaller than granularity.
>> +               The unit size is one block, now only support configuring in range
>> +               of [1, 512].
>> +
>>  What:          /sys/fs/f2fs/<disk>/max_victim_search
>>  Date:          January 2014
>>  Contact:       "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index e252e5bf9791..4b993961d81d 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -148,6 +148,8 @@ enum {
>>                 (BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
>>  #define MAX_DISCARD_BLOCKS(sbi)                BLKS_PER_SEC(sbi)
>>  #define DISCARD_ISSUE_RATE             8
>> +#define DEF_MIN_DISCARD_ISSUE_TIME     50      /* 50 ms, if exists */
>> +#define DEF_MAX_DISCARD_ISSUE_TIME     60000   /* 60 s, if no candidates */
>>  #define DEF_CP_INTERVAL                        60      /* 60 secs */
>>  #define DEF_IDLE_INTERVAL              5       /* 5 secs */
>>
>> @@ -196,11 +198,18 @@ struct discard_entry {
>>         unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard bitmap */
>>  };
>>
>> +/* default discard granularity of inner discard thread, unit: block count */
>> +#define DEFAULT_DISCARD_GRANULARITY            16
>> +
>>  /* max discard pend list number */
>>  #define MAX_PLIST_NUM          512
>>  #define plist_idx(blk_num)     ((blk_num) >= MAX_PLIST_NUM ?           \
>>                                         (MAX_PLIST_NUM - 1) : (blk_num - 1))
>>
>> +#define P_ACTIVE       0x01
>> +#define P_TRIM         0x02
>> +#define plist_issue(tag)       (((tag) & P_ACTIVE) || ((tag) & P_TRIM))
>> +
>>  enum {
>>         D_PREP,
>>         D_SUBMIT,
>> @@ -236,11 +245,14 @@ struct discard_cmd_control {
>>         struct task_struct *f2fs_issue_discard; /* discard thread */
>>         struct list_head entry_list;            /* 4KB discard entry list */
>>         struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
>> +       unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
>>         struct list_head wait_list;             /* store on-flushing entries */
>>         wait_queue_head_t discard_wait_queue;   /* waiting queue for wake-up */
>> +       unsigned int discard_wake;              /* to wake up discard thread */
>>         struct mutex cmd_lock;
>>         unsigned int nr_discards;               /* # of discards in the list */
>>         unsigned int max_discards;              /* max. discards to be issued */
>> +       unsigned int discard_granularity;       /* discard granularity */
>>         unsigned int undiscard_blks;            /* # of undiscard blocks */
>>         atomic_t issued_discard;                /* # of issued discard */
>>         atomic_t issing_discard;                /* # of issing discard */
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 05144b3a7f62..1387925a0d83 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -1016,32 +1016,65 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
>>         return 0;
>>  }
>>
>> -static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>> +static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>  {
>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>         struct list_head *pend_list;
>>         struct discard_cmd *dc, *tmp;
>>         struct blk_plug plug;
>> -       int i, iter = 0;
>> +       int iter = 0, issued = 0;
>> +       int i;
>>
>>         mutex_lock(&dcc->cmd_lock);
>>         f2fs_bug_on(sbi,
>>                 !__check_rb_tree_consistence(sbi, &dcc->root));
>>         blk_start_plug(&plug);
>> -       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>> +       for (i = MAX_PLIST_NUM - 1;
>> +                       i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
>>                 pend_list = &dcc->pend_list[i];
>>                 list_for_each_entry_safe(dc, tmp, pend_list, list) {
>>                         f2fs_bug_on(sbi, dc->state != D_PREP);
>>
>> -                       if (!issue_cond || is_idle(sbi))
>> +                       /* Hurry up to finish fstrim */
>> +                       if (dcc->pend_list_tag[i] & P_TRIM) {
>> +                               __submit_discard_cmd(sbi, dc);
>> +                               issued++;
>> +                               continue;
>> +                       }
>> +
>> +                       if (!issue_cond || is_idle(sbi)) {
>> +                               issued++;
>>                                 __submit_discard_cmd(sbi, dc);
>> +                       }
>>                         if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
>>                                 goto out;
>>                 }
>> +               if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
>> +                       dcc->pend_list_tag[i] &= (~P_TRIM);
>>         }
>>  out:
>>         blk_finish_plug(&plug);
>>         mutex_unlock(&dcc->cmd_lock);
>> +
>> +       return issued;
>> +}
>> +
>> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
>> +{
>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>> +       struct list_head *pend_list;
>> +       struct discard_cmd *dc, *tmp;
>> +       int i;
>> +
>> +       mutex_lock(&dcc->cmd_lock);
>> +       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>> +               pend_list = &dcc->pend_list[i];
>> +               list_for_each_entry_safe(dc, tmp, pend_list, list) {
>> +                       f2fs_bug_on(sbi, dc->state != D_PREP);
>> +                       __remove_discard_cmd(sbi, dc);
>> +               }
>> +       }
>> +       mutex_unlock(&dcc->cmd_lock);
>>  }
>>
>>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>> @@ -1126,34 +1159,56 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>>  {
>>         __issue_discard_cmd(sbi, false);
>> +       __drop_discard_cmd(sbi);
>>         __wait_discard_cmd(sbi, false);
>>  }
>>
>> +static void mark_discard_range_all(struct f2fs_sb_info *sbi)
>> +{
>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>> +       int i;
>> +
>> +       mutex_lock(&dcc->cmd_lock);
>> +       for (i = 0; i < MAX_PLIST_NUM; i++)
>> +               dcc->pend_list_tag[i] |= P_TRIM;
>> +       mutex_unlock(&dcc->cmd_lock);
>> +}
>> +
>>  static int issue_discard_thread(void *data)
>>  {
>>         struct f2fs_sb_info *sbi = data;
>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>         wait_queue_head_t *q = &dcc->discard_wait_queue;
>> +       unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>> +       int issued;
>>
>>         set_freezable();
>>
>>         do {
>> -               wait_event_interruptible(*q, kthread_should_stop() ||
>> -                                       freezing(current) ||
>> -                                       atomic_read(&dcc->discard_cmd_cnt));
>> +               wait_event_interruptible_timeout(*q,
>> +                               kthread_should_stop() || freezing(current) ||
>> +                               dcc->discard_wake,
>> +                               msecs_to_jiffies(wait_ms));
>>                 if (try_to_freeze())
>>                         continue;
>>                 if (kthread_should_stop())
>>                         return 0;
>>
>> +               if (dcc->discard_wake)
>> +                       dcc->discard_wake = 0;
>> +
>>                 sb_start_intwrite(sbi->sb);
>>
>> -               __issue_discard_cmd(sbi, true);
>> -               __wait_discard_cmd(sbi, true);
>> +               issued = __issue_discard_cmd(sbi, true);
>> +               if (issued) {
>> +                       __wait_discard_cmd(sbi, true);
>> +                       wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>> +               } else {
>> +                       wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
>> +               }
>>
>>                 sb_end_intwrite(sbi->sb);
>>
>> -               congestion_wait(BLK_RW_SYNC, HZ/50);
>>         } while (!kthread_should_stop());
>>         return 0;
>>  }
>> @@ -1344,7 +1399,8 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
>>
>>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>  {
>> -       struct list_head *head = &(SM_I(sbi)->dcc_info->entry_list);
>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>> +       struct list_head *head = &dcc->entry_list;
>>         struct discard_entry *entry, *this;
>>         struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
>>         unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
>> @@ -1426,11 +1482,12 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>                         goto find_next;
>>
>>                 list_del(&entry->list);
>> -               SM_I(sbi)->dcc_info->nr_discards -= total_len;
>> +               dcc->nr_discards -= total_len;
>>                 kmem_cache_free(discard_entry_slab, entry);
>>         }
>>
>> -       wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
>> +       dcc->discard_wake = 1;
>> +       wake_up_interruptible_all(&dcc->discard_wait_queue);
>>  }
>>
>>  static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>> @@ -1448,9 +1505,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>         if (!dcc)
>>                 return -ENOMEM;
>>
>> +       dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>>         INIT_LIST_HEAD(&dcc->entry_list);
>> -       for (i = 0; i < MAX_PLIST_NUM; i++)
>> +       for (i = 0; i < MAX_PLIST_NUM; i++) {
>>                 INIT_LIST_HEAD(&dcc->pend_list[i]);
>> +               if (i >= dcc->discard_granularity - 1)
>> +                       dcc->pend_list_tag[i] |= P_ACTIVE;
>> +       }
>>         INIT_LIST_HEAD(&dcc->wait_list);
>>         mutex_init(&dcc->cmd_lock);
>>         atomic_set(&dcc->issued_discard, 0);
>> @@ -2127,6 +2188,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>>
>>                 schedule();
>>         }
>> +       /* It's time to issue all the filed discards */
>> +       mark_discard_range_all(sbi);
>>  out:
>>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>>         return err;
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index c40e5d24df9f..4bcaa9059026 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>                 spin_unlock(&sbi->stat_lock);
>>                 return count;
>>         }
>> +
>> +       if (!strcmp(a->attr.name, "discard_granularity")) {
>> +               struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>> +               int i;
>> +
>> +               if (t == 0 || t > MAX_PLIST_NUM)
>> +                       return -EINVAL;
>> +               if (t == *ui)
>> +                       return count;
>> +
>> +               mutex_lock(&dcc->cmd_lock);
>> +               for (i = 0; i < MAX_PLIST_NUM; i++) {
>> +                       if (i >= t - 1)
>> +                               dcc->pend_list_tag[i] |= P_ACTIVE;
>> +                       else
>> +                               dcc->pend_list_tag[i] &= (~P_ACTIVE);
>> +               }
>> +               mutex_unlock(&dcc->cmd_lock);
>> +               return count;
>> +       }
>> +
>>         *ui = t;
>>
>>         if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
>> @@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
>> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
>> @@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
>>         ATTR_LIST(gc_urgent),
>>         ATTR_LIST(reclaim_segments),
>>         ATTR_LIST(max_small_discards),
>> +       ATTR_LIST(discard_granularity),
>>         ATTR_LIST(batched_trim_sections),
>>         ATTR_LIST(ipu_policy),
>>         ATTR_LIST(min_ipu_util),
>> --
>> 2.14.0.rc1.383.gd1ce394fe2-goog
>>
>>
>> ------------------------------------------------------------------------------
>> Check out the vibrant tech community on one of the world's most
>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [f2fs-dev] [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Ju Hyung Park]

Hi Chao.

Yep, that patch seems to have fixed it.
Doing "while true; do fstrim -v /; done" while "rm -rf"ing a 2GB
kbuild directory
(with lots of small .o files and stuff) ended flawlessly.

I hope to see this patch merged with next 4.14 merge cycle.

Thanks :)

On Tue, Oct 3, 2017 at 12:59 AM, Chao Yu <chao@kernel.org> wrote:
> Hi Park,
>
> Thanks for the report, could have a try with below patch:
>
> From 5fa30e8cdcb93f210e25142c48a884be383c6121 Mon Sep 17 00:00:00 2001
> From: Chao Yu <yuchao0@huawei.com>
> Date: Mon, 2 Oct 2017 02:50:16 +0800
> Subject: [PATCH] f2fs: fix potential panic during fstrim
>
> As Ju Hyung Park reported:
>
> "When 'fstrim' is called for manual trim, a BUG() can be triggered
> randomly with this patch.
>
> I'm seeing this issue on both x86 Desktop and arm64 Android phone.
>
> On x86 Desktop, this was caused during Ubuntu boot-up. I have a
> cronjob installed which calls 'fstrim -v /' during boot. On arm64
> Android, this was caused during GC looping with 1ms gc_min_sleep_time
> & gc_max_sleep_time."
>
> Root cause of this issue is that f2fs_wait_discard_bios can only be
> used by f2fs_put_super, because during put_super there must be no
> other referrers, so it can ignore discard entry's reference count
> when removing the entry, otherwise in other caller we will hit bug_on
> in __remove_discard_cmd as there may be other issuer added reference
> count in discard entry.
>
> Thread A                                Thread B
>                                         - issue_discard_thread
> - f2fs_ioc_fitrim
>  - f2fs_trim_fs
>   - f2fs_wait_discard_bios
>    - __issue_discard_cmd
>     - __submit_discard_cmd
>                                          - __wait_discard_cmd
>                                           - dc->ref++
>                                           - __wait_one_discard_bio
>    - __wait_discard_cmd
>     - __remove_discard_cmd
>      - f2fs_bug_on(sbi, dc->ref)
>
> Fixes: 969d1b180d987c2be02de890d0fff0f66a0e80de
> Reported-by: Ju Hyung Park <qkrwngud825@gmail.com>
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/f2fs/f2fs.h    | 2 +-
>  fs/f2fs/segment.c | 6 +++---
>  fs/f2fs/super.c   | 2 +-
>  3 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9a7c90386947..4b4a72f392be 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2525,7 +2525,7 @@ void invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr);
>  bool is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
>  void refresh_sit_entry(struct f2fs_sb_info *sbi, block_t old, block_t new);
>  void stop_discard_thread(struct f2fs_sb_info *sbi);
> -void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi);
> +void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount);
>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc);
>  void release_discard_addrs(struct f2fs_sb_info *sbi);
>  int npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index dedf0209d820..e28245b7e44e 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1210,11 +1210,11 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>  }
>
>  /* This comes from f2fs_put_super and f2fs_trim_fs */
> -void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
> +void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount)
>  {
>         __issue_discard_cmd(sbi, false);
>         __drop_discard_cmd(sbi);
> -       __wait_discard_cmd(sbi, false);
> +       __wait_discard_cmd(sbi, !umount);
>  }
>
>  static void mark_discard_range_all(struct f2fs_sb_info *sbi)
> @@ -2244,7 +2244,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>         }
>         /* It's time to issue all the filed discards */
>         mark_discard_range_all(sbi);
> -       f2fs_wait_discard_bios(sbi);
> +       f2fs_wait_discard_bios(sbi, false);
>  out:
>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>         return err;
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 89f61eb3d167..933c3d529e65 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -801,7 +801,7 @@ static void f2fs_put_super(struct super_block *sb)
>         }
>
>         /* be sure to wait for any on-going discard commands */
> -       f2fs_wait_discard_bios(sbi);
> +       f2fs_wait_discard_bios(sbi, true);
>
>         if (f2fs_discard_en(sbi) && !sbi->discard_blks) {
>                 struct cp_control cpc = {
> --
> 2.14.1.145.gb3622a4ee
>
> On 2017/10/2 3:29, Ju Hyung Park wrote:
>> When 'fstrim' is called for manual trim, a BUG() can be triggered
>> randomly with this patch.
>>
>> I'm seeing this issue on both x86 Desktop and arm64 Android phone.
>>
>> On x86 Desktop, this was caused during Ubuntu boot-up. I have a
>> cronjob installed
>> which calls 'fstrim -v /' during boot.
>> On arm64 Android, this was caused during GC looping with
>> 1ms gc_min_sleep_time & gc_max_sleep_time.
>>
>> Thanks.
>>
>> [26671.666421] ------------[ cut here ]------------
>> [26671.666426] WARNING: CPU: 8 PID: 103479 at fs/f2fs/segment.c:797
>> __remove_discard_cmd+0xb9/0xd0
>> [26671.666427] Modules linked in: ftdi_sio usbserial uas usb_storage
>> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
>> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
>> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
>> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
>> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
>> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
>> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
>> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
>> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
>> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
>> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
>> snd_seq_device
>> [26671.666450]  snd_timer snd soundcore k10temp i2c_piix4
>> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
>> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
>> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
>> async_pq async_xor async_tx raid1 multipath linear hid_generic
>> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
>> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
>> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
>> [26671.666471] CPU: 8 PID: 103479 Comm: fstrim Tainted: P           O
>>   4.13.4-zen+ #1
>> [26671.666472] Hardware name: System manufacturer System Product
>> Name/PRIME X399-A, BIOS 0318 08/11/2017
>> [26671.666472] task: ffff8804ad535800 task.stack: ffff88047ee38000
>> [26671.666474] RIP: 0010:__remove_discard_cmd+0xb9/0xd0
>> [26671.666474] RSP: 0018:ffff88047ee3bd00 EFLAGS: 00010202
>> [26671.666475] RAX: ffff88081801a500 RBX: ffff88047eeaed00 RCX: ffff88047eeaedf8
>> [26671.666475] RDX: 0000000000000001 RSI: ffff88047eeaed00 RDI: ffff880802555800
>> [26671.666476] RBP: ffff8808134d0000 R08: ffff8804ad535800 R09: 0000000000000001
>> [26671.666476] R10: ffff88047ee3bd18 R11: 0000000000000000 R12: ffff880802555800
>> [26671.666476] R13: 0000000000000000 R14: ffff88047eeaedd0 R15: ffff8808134d0000
>> [26671.666477] FS:  00007f44cddad2c0(0000) GS:ffff88081ca00000(0000)
>> knlGS:0000000000000000
>> [26671.666478] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [26671.666478] CR2: 00007f88f5776328 CR3: 000000058ce4a000 CR4: 00000000003406e0
>> [26671.666479] Call Trace:
>> [26671.666481]  ? __wait_discard_cmd+0x7a/0xc0
>> [26671.666482]  ? f2fs_trim_fs+0x1c1/0x210
>> [26671.666484]  ? f2fs_ioctl+0x75a/0x2320
>> [26671.666486]  ? do_filp_open+0x99/0xe0
>> [26671.666487]  ? cp_new_stat+0x138/0x150
>> [26671.666489]  ? do_vfs_ioctl+0x88/0x5c0
>> [26671.666490]  ? SyS_newfstat+0x29/0x40
>> [26671.666491]  ? SyS_ioctl+0x6f/0x80
>> [26671.666493]  ? entry_SYSCALL_64_fastpath+0x1e/0xa9
>> [26671.666493] Code: 48 89 de 8b 43 1c 48 8b 3d 4d 8c 31 01 29 85 74
>> 22 00 00 e8 fa 01 d5 ff f0 ff 8d 80 22 00 00 5b 5d c3 c7 43 64 00 00
>> 00 00 eb 92 <0f> ff f0 80 4f 20 04 e9 53 ff ff ff 90 66 2e 0f 1f 84 00
>> 00 00
>> [26671.666506] ---[ end trace 613553f7a4728b5a ]---
>> [26672.553742] general protection fault: 0000 [#1] PREEMPT SMP
>> [26672.553746] Modules linked in: ftdi_sio usbserial uas usb_storage
>> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
>> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
>> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
>> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
>> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
>> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
>> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
>> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
>> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
>> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
>> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
>> snd_seq_device
>> [26672.553771]  snd_timer snd soundcore k10temp i2c_piix4
>> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
>> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
>> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
>> async_pq async_xor async_tx raid1 multipath linear hid_generic
>> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
>> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
>> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
>> [26672.553792] CPU: 10 PID: 1287 Comm: f2fs_discard-25 Tainted: P
>>   W  O    4.13.4-zen+ #1
>> [26672.553793] Hardware name: System manufacturer System Product
>> Name/PRIME X399-A, BIOS 0318 08/11/2017
>> [26672.553794] task: ffff8808159c1600 task.stack: ffff880813304000
>> [26672.553798] RIP: 0010:__remove_discard_cmd+0x6a/0xd0
>> [26672.553799] RSP: 0018:ffff880813307e20 EFLAGS: 00010296
>> [26672.553800] RAX: dead000000000200 RBX: ffff88047eeaed00 RCX: ffff8808159c1601
>> [26672.553801] RDX: dead000000000100 RSI: ffff8808134d2288 RDI: ffff88047eeaed00
>> [26672.553801] RBP: ffff8808134d0000 R08: 0000184230172c00 R09: 0000000000000006
>> [26672.553802] R10: ffff880813307e38 R11: 0000000000000023 R12: ffff880802555800
>> [26672.553803] R13: 0000000000000001 R14: ffff88047eeaed00 R15: ffff8808134d0000
>> [26672.553804] FS:  0000000000000000(0000) GS:ffff88081ca80000(0000)
>> knlGS:0000000000000000
>> [26672.553805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [26672.553805] CR2: 00007f88f2f71328 CR3: 000000048be79000 CR4: 00000000003406e0
>> [26672.553806] Call Trace:
>> [26672.553808]  ? __wait_one_discard_bio+0x41/0x60
>> [26672.553809]  ? __wait_discard_cmd+0xbb/0xc0
>> [26672.553811]  ? issue_discard_thread+0x196/0x200
>> [26672.553813]  ? wait_woken+0x80/0x80
>> [26672.553814]  ? mark_discard_range_all.isra.11+0x40/0x40
>> [26672.553816]  ? kthread+0x112/0x130
>> [26672.553817]  ? kthread_create_on_node+0x40/0x40
>> [26672.553818]  ? do_group_exit+0x2e/0xa0
>> [26672.553820]  ? ret_from_fork+0x25/0x30
>> [26672.553821] Code: 8b 43 20 48 8b 3f e8 56 6c fe ff 58 80 7b 62 02
>> 75 07 f0 ff 8d 7c 22 00 00 48 8b 53 28 48 8b 43 30 48 8d b5 88 22 00
>> 00 48 89 df <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89
>> 43 28
>> [26672.553835] RIP: __remove_discard_cmd+0x6a/0xd0 RSP: ffff880813307e20
>> [26672.553836] ---[ end trace 613553f7a4728b5b ]---
>>
>> On Tue, Aug 22, 2017 at 5:42 AM, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
>>> On 08/18, Chao Yu wrote:
>>>> Hi Jaegeuk,
>>>>
>>>> Sorry for the delay, the modification looks good to me. ;)
>>>
>>> We must avoid waking up discard thread caused by # of pending commands
>>> which are never issued.
>>>
>>> From a73f8807248c2f42328a2204eab16a3b8d32c83e Mon Sep 17 00:00:00 2001
>>> From: Chao Yu <yuchao0@huawei.com>
>>> Date: Mon, 7 Aug 2017 23:09:56 +0800
>>> Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry
>>>
>>> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
>>> f2fs to issue 4K size discard in real-time discard mode. However, issuing
>>> smaller discard may cost more lifetime but releasing less free space in
>>> flash device. Since f2fs has ability of separating hot/cold data and
>>> garbage collection, we can expect that small-sized invalid region would
>>> expand soon with OPU, deletion or garbage collection on valid datas, so
>>> it's better to delay or skip issuing smaller size discards, it could help
>>> to reduce overmuch consumption of IO bandwidth and lifetime of flash
>>> storage.
>>>
>>> This patch makes f2fs selectng 64K size as its default minimal
>>> granularity, and issue discard with the size which is not smaller than
>>> minimal granularity. Also it exposes discard granularity as sysfs entry
>>> for configuration in different scenario.
>>>
>>> Jaegeuk Kim:
>>>  We must issue all the accumulated discard commands when fstrim is called.
>>>  So, I've added pend_list_tag[] to indicate whether we should issue the
>>>  commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
>>>  P_TRIM is set once at a time, given fstrim trigger.
>>>  In addition, issue_discard_thread is calling too much due to the number of
>>>  discard commands remaining in the pending list. I added a timer to control
>>>  it likewise gc_thread.
>>>
>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>> ---
>>>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 ++++
>>>  fs/f2fs/f2fs.h                          | 12 +++++
>>>  fs/f2fs/segment.c                       | 91 ++++++++++++++++++++++++++++-----
>>>  fs/f2fs/sysfs.c                         | 23 +++++++++
>>>  4 files changed, 121 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>>> index 621da3fc56c5..11b7f4ebea7c 100644
>>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>>> @@ -57,6 +57,15 @@ Contact:     "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>>>  Description:
>>>                  Controls the issue rate of small discard commands.
>>>
>>> +What:          /sys/fs/f2fs/<disk>/discard_granularity
>>> +Date:          July 2017
>>> +Contact:       "Chao Yu" <yuchao0@huawei.com>
>>> +Description:
>>> +               Controls discard granularity of inner discard thread, inner thread
>>> +               will not issue discards with size that is smaller than granularity.
>>> +               The unit size is one block, now only support configuring in range
>>> +               of [1, 512].
>>> +
>>>  What:          /sys/fs/f2fs/<disk>/max_victim_search
>>>  Date:          January 2014
>>>  Contact:       "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index e252e5bf9791..4b993961d81d 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -148,6 +148,8 @@ enum {
>>>                 (BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
>>>  #define MAX_DISCARD_BLOCKS(sbi)                BLKS_PER_SEC(sbi)
>>>  #define DISCARD_ISSUE_RATE             8
>>> +#define DEF_MIN_DISCARD_ISSUE_TIME     50      /* 50 ms, if exists */
>>> +#define DEF_MAX_DISCARD_ISSUE_TIME     60000   /* 60 s, if no candidates */
>>>  #define DEF_CP_INTERVAL                        60      /* 60 secs */
>>>  #define DEF_IDLE_INTERVAL              5       /* 5 secs */
>>>
>>> @@ -196,11 +198,18 @@ struct discard_entry {
>>>         unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard bitmap */
>>>  };
>>>
>>> +/* default discard granularity of inner discard thread, unit: block count */
>>> +#define DEFAULT_DISCARD_GRANULARITY            16
>>> +
>>>  /* max discard pend list number */
>>>  #define MAX_PLIST_NUM          512
>>>  #define plist_idx(blk_num)     ((blk_num) >= MAX_PLIST_NUM ?           \
>>>                                         (MAX_PLIST_NUM - 1) : (blk_num - 1))
>>>
>>> +#define P_ACTIVE       0x01
>>> +#define P_TRIM         0x02
>>> +#define plist_issue(tag)       (((tag) & P_ACTIVE) || ((tag) & P_TRIM))
>>> +
>>>  enum {
>>>         D_PREP,
>>>         D_SUBMIT,
>>> @@ -236,11 +245,14 @@ struct discard_cmd_control {
>>>         struct task_struct *f2fs_issue_discard; /* discard thread */
>>>         struct list_head entry_list;            /* 4KB discard entry list */
>>>         struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
>>> +       unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
>>>         struct list_head wait_list;             /* store on-flushing entries */
>>>         wait_queue_head_t discard_wait_queue;   /* waiting queue for wake-up */
>>> +       unsigned int discard_wake;              /* to wake up discard thread */
>>>         struct mutex cmd_lock;
>>>         unsigned int nr_discards;               /* # of discards in the list */
>>>         unsigned int max_discards;              /* max. discards to be issued */
>>> +       unsigned int discard_granularity;       /* discard granularity */
>>>         unsigned int undiscard_blks;            /* # of undiscard blocks */
>>>         atomic_t issued_discard;                /* # of issued discard */
>>>         atomic_t issing_discard;                /* # of issing discard */
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index 05144b3a7f62..1387925a0d83 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -1016,32 +1016,65 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
>>>         return 0;
>>>  }
>>>
>>> -static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>> +static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>>  {
>>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>         struct list_head *pend_list;
>>>         struct discard_cmd *dc, *tmp;
>>>         struct blk_plug plug;
>>> -       int i, iter = 0;
>>> +       int iter = 0, issued = 0;
>>> +       int i;
>>>
>>>         mutex_lock(&dcc->cmd_lock);
>>>         f2fs_bug_on(sbi,
>>>                 !__check_rb_tree_consistence(sbi, &dcc->root));
>>>         blk_start_plug(&plug);
>>> -       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>>> +       for (i = MAX_PLIST_NUM - 1;
>>> +                       i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
>>>                 pend_list = &dcc->pend_list[i];
>>>                 list_for_each_entry_safe(dc, tmp, pend_list, list) {
>>>                         f2fs_bug_on(sbi, dc->state != D_PREP);
>>>
>>> -                       if (!issue_cond || is_idle(sbi))
>>> +                       /* Hurry up to finish fstrim */
>>> +                       if (dcc->pend_list_tag[i] & P_TRIM) {
>>> +                               __submit_discard_cmd(sbi, dc);
>>> +                               issued++;
>>> +                               continue;
>>> +                       }
>>> +
>>> +                       if (!issue_cond || is_idle(sbi)) {
>>> +                               issued++;
>>>                                 __submit_discard_cmd(sbi, dc);
>>> +                       }
>>>                         if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
>>>                                 goto out;
>>>                 }
>>> +               if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
>>> +                       dcc->pend_list_tag[i] &= (~P_TRIM);
>>>         }
>>>  out:
>>>         blk_finish_plug(&plug);
>>>         mutex_unlock(&dcc->cmd_lock);
>>> +
>>> +       return issued;
>>> +}
>>> +
>>> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
>>> +{
>>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>> +       struct list_head *pend_list;
>>> +       struct discard_cmd *dc, *tmp;
>>> +       int i;
>>> +
>>> +       mutex_lock(&dcc->cmd_lock);
>>> +       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>>> +               pend_list = &dcc->pend_list[i];
>>> +               list_for_each_entry_safe(dc, tmp, pend_list, list) {
>>> +                       f2fs_bug_on(sbi, dc->state != D_PREP);
>>> +                       __remove_discard_cmd(sbi, dc);
>>> +               }
>>> +       }
>>> +       mutex_unlock(&dcc->cmd_lock);
>>>  }
>>>
>>>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>>> @@ -1126,34 +1159,56 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>>>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>>>  {
>>>         __issue_discard_cmd(sbi, false);
>>> +       __drop_discard_cmd(sbi);
>>>         __wait_discard_cmd(sbi, false);
>>>  }
>>>
>>> +static void mark_discard_range_all(struct f2fs_sb_info *sbi)
>>> +{
>>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>> +       int i;
>>> +
>>> +       mutex_lock(&dcc->cmd_lock);
>>> +       for (i = 0; i < MAX_PLIST_NUM; i++)
>>> +               dcc->pend_list_tag[i] |= P_TRIM;
>>> +       mutex_unlock(&dcc->cmd_lock);
>>> +}
>>> +
>>>  static int issue_discard_thread(void *data)
>>>  {
>>>         struct f2fs_sb_info *sbi = data;
>>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>         wait_queue_head_t *q = &dcc->discard_wait_queue;
>>> +       unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>>> +       int issued;
>>>
>>>         set_freezable();
>>>
>>>         do {
>>> -               wait_event_interruptible(*q, kthread_should_stop() ||
>>> -                                       freezing(current) ||
>>> -                                       atomic_read(&dcc->discard_cmd_cnt));
>>> +               wait_event_interruptible_timeout(*q,
>>> +                               kthread_should_stop() || freezing(current) ||
>>> +                               dcc->discard_wake,
>>> +                               msecs_to_jiffies(wait_ms));
>>>                 if (try_to_freeze())
>>>                         continue;
>>>                 if (kthread_should_stop())
>>>                         return 0;
>>>
>>> +               if (dcc->discard_wake)
>>> +                       dcc->discard_wake = 0;
>>> +
>>>                 sb_start_intwrite(sbi->sb);
>>>
>>> -               __issue_discard_cmd(sbi, true);
>>> -               __wait_discard_cmd(sbi, true);
>>> +               issued = __issue_discard_cmd(sbi, true);
>>> +               if (issued) {
>>> +                       __wait_discard_cmd(sbi, true);
>>> +                       wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>>> +               } else {
>>> +                       wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
>>> +               }
>>>
>>>                 sb_end_intwrite(sbi->sb);
>>>
>>> -               congestion_wait(BLK_RW_SYNC, HZ/50);
>>>         } while (!kthread_should_stop());
>>>         return 0;
>>>  }
>>> @@ -1344,7 +1399,8 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
>>>
>>>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>  {
>>> -       struct list_head *head = &(SM_I(sbi)->dcc_info->entry_list);
>>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>> +       struct list_head *head = &dcc->entry_list;
>>>         struct discard_entry *entry, *this;
>>>         struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
>>>         unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
>>> @@ -1426,11 +1482,12 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>                         goto find_next;
>>>
>>>                 list_del(&entry->list);
>>> -               SM_I(sbi)->dcc_info->nr_discards -= total_len;
>>> +               dcc->nr_discards -= total_len;
>>>                 kmem_cache_free(discard_entry_slab, entry);
>>>         }
>>>
>>> -       wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
>>> +       dcc->discard_wake = 1;
>>> +       wake_up_interruptible_all(&dcc->discard_wait_queue);
>>>  }
>>>
>>>  static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>> @@ -1448,9 +1505,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>>         if (!dcc)
>>>                 return -ENOMEM;
>>>
>>> +       dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>>>         INIT_LIST_HEAD(&dcc->entry_list);
>>> -       for (i = 0; i < MAX_PLIST_NUM; i++)
>>> +       for (i = 0; i < MAX_PLIST_NUM; i++) {
>>>                 INIT_LIST_HEAD(&dcc->pend_list[i]);
>>> +               if (i >= dcc->discard_granularity - 1)
>>> +                       dcc->pend_list_tag[i] |= P_ACTIVE;
>>> +       }
>>>         INIT_LIST_HEAD(&dcc->wait_list);
>>>         mutex_init(&dcc->cmd_lock);
>>>         atomic_set(&dcc->issued_discard, 0);
>>> @@ -2127,6 +2188,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>>>
>>>                 schedule();
>>>         }
>>> +       /* It's time to issue all the filed discards */
>>> +       mark_discard_range_all(sbi);
>>>  out:
>>>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>>>         return err;
>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>> index c40e5d24df9f..4bcaa9059026 100644
>>> --- a/fs/f2fs/sysfs.c
>>> +++ b/fs/f2fs/sysfs.c
>>> @@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>>                 spin_unlock(&sbi->stat_lock);
>>>                 return count;
>>>         }
>>> +
>>> +       if (!strcmp(a->attr.name, "discard_granularity")) {
>>> +               struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>> +               int i;
>>> +
>>> +               if (t == 0 || t > MAX_PLIST_NUM)
>>> +                       return -EINVAL;
>>> +               if (t == *ui)
>>> +                       return count;
>>> +
>>> +               mutex_lock(&dcc->cmd_lock);
>>> +               for (i = 0; i < MAX_PLIST_NUM; i++) {
>>> +                       if (i >= t - 1)
>>> +                               dcc->pend_list_tag[i] |= P_ACTIVE;
>>> +                       else
>>> +                               dcc->pend_list_tag[i] &= (~P_ACTIVE);
>>> +               }
>>> +               mutex_unlock(&dcc->cmd_lock);
>>> +               return count;
>>> +       }
>>> +
>>>         *ui = t;
>>>
>>>         if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
>>> @@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>>>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
>>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>>>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
>>> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>>>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
>>> @@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
>>>         ATTR_LIST(gc_urgent),
>>>         ATTR_LIST(reclaim_segments),
>>>         ATTR_LIST(max_small_discards),
>>> +       ATTR_LIST(discard_granularity),
>>>         ATTR_LIST(batched_trim_sections),
>>>         ATTR_LIST(ipu_policy),
>>>         ATTR_LIST(min_ipu_util),
>>> --
>>> 2.14.0.rc1.383.gd1ce394fe2-goog
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Check out the vibrant tech community on one of the world's most
>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>> _______________________________________________
>>> Linux-f2fs-devel mailing list
>>> Linux-f2fs-devel@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [f2fs-dev] [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Jaegeuk Kim]

On 10/04, Ju Hyung Park wrote:
> Hi Chao.
> 
> Yep, that patch seems to have fixed it.
> Doing "while true; do fstrim -v /; done" while "rm -rf"ing a 2GB
> kbuild directory
> (with lots of small .o files and stuff) ended flawlessly.
> 
> I hope to see this patch merged with next 4.14 merge cycle.

Cool! I'll merge this patch and submit for 4.14. :)

Thanks,

> 
> Thanks :)
> 
> On Tue, Oct 3, 2017 at 12:59 AM, Chao Yu <chao@kernel.org> wrote:
> > Hi Park,
> >
> > Thanks for the report, could have a try with below patch:
> >
> > From 5fa30e8cdcb93f210e25142c48a884be383c6121 Mon Sep 17 00:00:00 2001
> > From: Chao Yu <yuchao0@huawei.com>
> > Date: Mon, 2 Oct 2017 02:50:16 +0800
> > Subject: [PATCH] f2fs: fix potential panic during fstrim
> >
> > As Ju Hyung Park reported:
> >
> > "When 'fstrim' is called for manual trim, a BUG() can be triggered
> > randomly with this patch.
> >
> > I'm seeing this issue on both x86 Desktop and arm64 Android phone.
> >
> > On x86 Desktop, this was caused during Ubuntu boot-up. I have a
> > cronjob installed which calls 'fstrim -v /' during boot. On arm64
> > Android, this was caused during GC looping with 1ms gc_min_sleep_time
> > & gc_max_sleep_time."
> >
> > Root cause of this issue is that f2fs_wait_discard_bios can only be
> > used by f2fs_put_super, because during put_super there must be no
> > other referrers, so it can ignore discard entry's reference count
> > when removing the entry, otherwise in other caller we will hit bug_on
> > in __remove_discard_cmd as there may be other issuer added reference
> > count in discard entry.
> >
> > Thread A                                Thread B
> >                                         - issue_discard_thread
> > - f2fs_ioc_fitrim
> >  - f2fs_trim_fs
> >   - f2fs_wait_discard_bios
> >    - __issue_discard_cmd
> >     - __submit_discard_cmd
> >                                          - __wait_discard_cmd
> >                                           - dc->ref++
> >                                           - __wait_one_discard_bio
> >    - __wait_discard_cmd
> >     - __remove_discard_cmd
> >      - f2fs_bug_on(sbi, dc->ref)
> >
> > Fixes: 969d1b180d987c2be02de890d0fff0f66a0e80de
> > Reported-by: Ju Hyung Park <qkrwngud825@gmail.com>
> > Signed-off-by: Chao Yu <yuchao0@huawei.com>
> > ---
> >  fs/f2fs/f2fs.h    | 2 +-
> >  fs/f2fs/segment.c | 6 +++---
> >  fs/f2fs/super.c   | 2 +-
> >  3 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 9a7c90386947..4b4a72f392be 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -2525,7 +2525,7 @@ void invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr);
> >  bool is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
> >  void refresh_sit_entry(struct f2fs_sb_info *sbi, block_t old, block_t new);
> >  void stop_discard_thread(struct f2fs_sb_info *sbi);
> > -void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi);
> > +void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount);
> >  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc);
> >  void release_discard_addrs(struct f2fs_sb_info *sbi);
> >  int npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index dedf0209d820..e28245b7e44e 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1210,11 +1210,11 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
> >  }
> >
> >  /* This comes from f2fs_put_super and f2fs_trim_fs */
> > -void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
> > +void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount)
> >  {
> >         __issue_discard_cmd(sbi, false);
> >         __drop_discard_cmd(sbi);
> > -       __wait_discard_cmd(sbi, false);
> > +       __wait_discard_cmd(sbi, !umount);
> >  }
> >
> >  static void mark_discard_range_all(struct f2fs_sb_info *sbi)
> > @@ -2244,7 +2244,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
> >         }
> >         /* It's time to issue all the filed discards */
> >         mark_discard_range_all(sbi);
> > -       f2fs_wait_discard_bios(sbi);
> > +       f2fs_wait_discard_bios(sbi, false);
> >  out:
> >         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
> >         return err;
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 89f61eb3d167..933c3d529e65 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -801,7 +801,7 @@ static void f2fs_put_super(struct super_block *sb)
> >         }
> >
> >         /* be sure to wait for any on-going discard commands */
> > -       f2fs_wait_discard_bios(sbi);
> > +       f2fs_wait_discard_bios(sbi, true);
> >
> >         if (f2fs_discard_en(sbi) && !sbi->discard_blks) {
> >                 struct cp_control cpc = {
> > --
> > 2.14.1.145.gb3622a4ee
> >
> > On 2017/10/2 3:29, Ju Hyung Park wrote:
> >> When 'fstrim' is called for manual trim, a BUG() can be triggered
> >> randomly with this patch.
> >>
> >> I'm seeing this issue on both x86 Desktop and arm64 Android phone.
> >>
> >> On x86 Desktop, this was caused during Ubuntu boot-up. I have a
> >> cronjob installed
> >> which calls 'fstrim -v /' during boot.
> >> On arm64 Android, this was caused during GC looping with
> >> 1ms gc_min_sleep_time & gc_max_sleep_time.
> >>
> >> Thanks.
> >>
> >> [26671.666421] ------------[ cut here ]------------
> >> [26671.666426] WARNING: CPU: 8 PID: 103479 at fs/f2fs/segment.c:797
> >> __remove_discard_cmd+0xb9/0xd0
> >> [26671.666427] Modules linked in: ftdi_sio usbserial uas usb_storage
> >> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
> >> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
> >> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
> >> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
> >> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
> >> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
> >> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
> >> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
> >> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
> >> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
> >> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
> >> snd_seq_device
> >> [26671.666450]  snd_timer snd soundcore k10temp i2c_piix4
> >> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
> >> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
> >> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
> >> async_pq async_xor async_tx raid1 multipath linear hid_generic
> >> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
> >> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
> >> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
> >> [26671.666471] CPU: 8 PID: 103479 Comm: fstrim Tainted: P           O
> >>   4.13.4-zen+ #1
> >> [26671.666472] Hardware name: System manufacturer System Product
> >> Name/PRIME X399-A, BIOS 0318 08/11/2017
> >> [26671.666472] task: ffff8804ad535800 task.stack: ffff88047ee38000
> >> [26671.666474] RIP: 0010:__remove_discard_cmd+0xb9/0xd0
> >> [26671.666474] RSP: 0018:ffff88047ee3bd00 EFLAGS: 00010202
> >> [26671.666475] RAX: ffff88081801a500 RBX: ffff88047eeaed00 RCX: ffff88047eeaedf8
> >> [26671.666475] RDX: 0000000000000001 RSI: ffff88047eeaed00 RDI: ffff880802555800
> >> [26671.666476] RBP: ffff8808134d0000 R08: ffff8804ad535800 R09: 0000000000000001
> >> [26671.666476] R10: ffff88047ee3bd18 R11: 0000000000000000 R12: ffff880802555800
> >> [26671.666476] R13: 0000000000000000 R14: ffff88047eeaedd0 R15: ffff8808134d0000
> >> [26671.666477] FS:  00007f44cddad2c0(0000) GS:ffff88081ca00000(0000)
> >> knlGS:0000000000000000
> >> [26671.666478] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> [26671.666478] CR2: 00007f88f5776328 CR3: 000000058ce4a000 CR4: 00000000003406e0
> >> [26671.666479] Call Trace:
> >> [26671.666481]  ? __wait_discard_cmd+0x7a/0xc0
> >> [26671.666482]  ? f2fs_trim_fs+0x1c1/0x210
> >> [26671.666484]  ? f2fs_ioctl+0x75a/0x2320
> >> [26671.666486]  ? do_filp_open+0x99/0xe0
> >> [26671.666487]  ? cp_new_stat+0x138/0x150
> >> [26671.666489]  ? do_vfs_ioctl+0x88/0x5c0
> >> [26671.666490]  ? SyS_newfstat+0x29/0x40
> >> [26671.666491]  ? SyS_ioctl+0x6f/0x80
> >> [26671.666493]  ? entry_SYSCALL_64_fastpath+0x1e/0xa9
> >> [26671.666493] Code: 48 89 de 8b 43 1c 48 8b 3d 4d 8c 31 01 29 85 74
> >> 22 00 00 e8 fa 01 d5 ff f0 ff 8d 80 22 00 00 5b 5d c3 c7 43 64 00 00
> >> 00 00 eb 92 <0f> ff f0 80 4f 20 04 e9 53 ff ff ff 90 66 2e 0f 1f 84 00
> >> 00 00
> >> [26671.666506] ---[ end trace 613553f7a4728b5a ]---
> >> [26672.553742] general protection fault: 0000 [#1] PREEMPT SMP
> >> [26672.553746] Modules linked in: ftdi_sio usbserial uas usb_storage
> >> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
> >> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
> >> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
> >> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
> >> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
> >> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
> >> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
> >> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
> >> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
> >> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
> >> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
> >> snd_seq_device
> >> [26672.553771]  snd_timer snd soundcore k10temp i2c_piix4
> >> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
> >> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
> >> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
> >> async_pq async_xor async_tx raid1 multipath linear hid_generic
> >> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
> >> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
> >> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
> >> [26672.553792] CPU: 10 PID: 1287 Comm: f2fs_discard-25 Tainted: P
> >>   W  O    4.13.4-zen+ #1
> >> [26672.553793] Hardware name: System manufacturer System Product
> >> Name/PRIME X399-A, BIOS 0318 08/11/2017
> >> [26672.553794] task: ffff8808159c1600 task.stack: ffff880813304000
> >> [26672.553798] RIP: 0010:__remove_discard_cmd+0x6a/0xd0
> >> [26672.553799] RSP: 0018:ffff880813307e20 EFLAGS: 00010296
> >> [26672.553800] RAX: dead000000000200 RBX: ffff88047eeaed00 RCX: ffff8808159c1601
> >> [26672.553801] RDX: dead000000000100 RSI: ffff8808134d2288 RDI: ffff88047eeaed00
> >> [26672.553801] RBP: ffff8808134d0000 R08: 0000184230172c00 R09: 0000000000000006
> >> [26672.553802] R10: ffff880813307e38 R11: 0000000000000023 R12: ffff880802555800
> >> [26672.553803] R13: 0000000000000001 R14: ffff88047eeaed00 R15: ffff8808134d0000
> >> [26672.553804] FS:  0000000000000000(0000) GS:ffff88081ca80000(0000)
> >> knlGS:0000000000000000
> >> [26672.553805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> [26672.553805] CR2: 00007f88f2f71328 CR3: 000000048be79000 CR4: 00000000003406e0
> >> [26672.553806] Call Trace:
> >> [26672.553808]  ? __wait_one_discard_bio+0x41/0x60
> >> [26672.553809]  ? __wait_discard_cmd+0xbb/0xc0
> >> [26672.553811]  ? issue_discard_thread+0x196/0x200
> >> [26672.553813]  ? wait_woken+0x80/0x80
> >> [26672.553814]  ? mark_discard_range_all.isra.11+0x40/0x40
> >> [26672.553816]  ? kthread+0x112/0x130
> >> [26672.553817]  ? kthread_create_on_node+0x40/0x40
> >> [26672.553818]  ? do_group_exit+0x2e/0xa0
> >> [26672.553820]  ? ret_from_fork+0x25/0x30
> >> [26672.553821] Code: 8b 43 20 48 8b 3f e8 56 6c fe ff 58 80 7b 62 02
> >> 75 07 f0 ff 8d 7c 22 00 00 48 8b 53 28 48 8b 43 30 48 8d b5 88 22 00
> >> 00 48 89 df <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89
> >> 43 28
> >> [26672.553835] RIP: __remove_discard_cmd+0x6a/0xd0 RSP: ffff880813307e20
> >> [26672.553836] ---[ end trace 613553f7a4728b5b ]---
> >>
> >> On Tue, Aug 22, 2017 at 5:42 AM, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
> >>> On 08/18, Chao Yu wrote:
> >>>> Hi Jaegeuk,
> >>>>
> >>>> Sorry for the delay, the modification looks good to me. ;)
> >>>
> >>> We must avoid waking up discard thread caused by # of pending commands
> >>> which are never issued.
> >>>
> >>> From a73f8807248c2f42328a2204eab16a3b8d32c83e Mon Sep 17 00:00:00 2001
> >>> From: Chao Yu <yuchao0@huawei.com>
> >>> Date: Mon, 7 Aug 2017 23:09:56 +0800
> >>> Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry
> >>>
> >>> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
> >>> f2fs to issue 4K size discard in real-time discard mode. However, issuing
> >>> smaller discard may cost more lifetime but releasing less free space in
> >>> flash device. Since f2fs has ability of separating hot/cold data and
> >>> garbage collection, we can expect that small-sized invalid region would
> >>> expand soon with OPU, deletion or garbage collection on valid datas, so
> >>> it's better to delay or skip issuing smaller size discards, it could help
> >>> to reduce overmuch consumption of IO bandwidth and lifetime of flash
> >>> storage.
> >>>
> >>> This patch makes f2fs selectng 64K size as its default minimal
> >>> granularity, and issue discard with the size which is not smaller than
> >>> minimal granularity. Also it exposes discard granularity as sysfs entry
> >>> for configuration in different scenario.
> >>>
> >>> Jaegeuk Kim:
> >>>  We must issue all the accumulated discard commands when fstrim is called.
> >>>  So, I've added pend_list_tag[] to indicate whether we should issue the
> >>>  commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
> >>>  P_TRIM is set once at a time, given fstrim trigger.
> >>>  In addition, issue_discard_thread is calling too much due to the number of
> >>>  discard commands remaining in the pending list. I added a timer to control
> >>>  it likewise gc_thread.
> >>>
> >>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> >>> ---
> >>>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 ++++
> >>>  fs/f2fs/f2fs.h                          | 12 +++++
> >>>  fs/f2fs/segment.c                       | 91 ++++++++++++++++++++++++++++-----
> >>>  fs/f2fs/sysfs.c                         | 23 +++++++++
> >>>  4 files changed, 121 insertions(+), 14 deletions(-)
> >>>
> >>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> >>> index 621da3fc56c5..11b7f4ebea7c 100644
> >>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> >>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> >>> @@ -57,6 +57,15 @@ Contact:     "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
> >>>  Description:
> >>>                  Controls the issue rate of small discard commands.
> >>>
> >>> +What:          /sys/fs/f2fs/<disk>/discard_granularity
> >>> +Date:          July 2017
> >>> +Contact:       "Chao Yu" <yuchao0@huawei.com>
> >>> +Description:
> >>> +               Controls discard granularity of inner discard thread, inner thread
> >>> +               will not issue discards with size that is smaller than granularity.
> >>> +               The unit size is one block, now only support configuring in range
> >>> +               of [1, 512].
> >>> +
> >>>  What:          /sys/fs/f2fs/<disk>/max_victim_search
> >>>  Date:          January 2014
> >>>  Contact:       "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
> >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >>> index e252e5bf9791..4b993961d81d 100644
> >>> --- a/fs/f2fs/f2fs.h
> >>> +++ b/fs/f2fs/f2fs.h
> >>> @@ -148,6 +148,8 @@ enum {
> >>>                 (BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
> >>>  #define MAX_DISCARD_BLOCKS(sbi)                BLKS_PER_SEC(sbi)
> >>>  #define DISCARD_ISSUE_RATE             8
> >>> +#define DEF_MIN_DISCARD_ISSUE_TIME     50      /* 50 ms, if exists */
> >>> +#define DEF_MAX_DISCARD_ISSUE_TIME     60000   /* 60 s, if no candidates */
> >>>  #define DEF_CP_INTERVAL                        60      /* 60 secs */
> >>>  #define DEF_IDLE_INTERVAL              5       /* 5 secs */
> >>>
> >>> @@ -196,11 +198,18 @@ struct discard_entry {
> >>>         unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard bitmap */
> >>>  };
> >>>
> >>> +/* default discard granularity of inner discard thread, unit: block count */
> >>> +#define DEFAULT_DISCARD_GRANULARITY            16
> >>> +
> >>>  /* max discard pend list number */
> >>>  #define MAX_PLIST_NUM          512
> >>>  #define plist_idx(blk_num)     ((blk_num) >= MAX_PLIST_NUM ?           \
> >>>                                         (MAX_PLIST_NUM - 1) : (blk_num - 1))
> >>>
> >>> +#define P_ACTIVE       0x01
> >>> +#define P_TRIM         0x02
> >>> +#define plist_issue(tag)       (((tag) & P_ACTIVE) || ((tag) & P_TRIM))
> >>> +
> >>>  enum {
> >>>         D_PREP,
> >>>         D_SUBMIT,
> >>> @@ -236,11 +245,14 @@ struct discard_cmd_control {
> >>>         struct task_struct *f2fs_issue_discard; /* discard thread */
> >>>         struct list_head entry_list;            /* 4KB discard entry list */
> >>>         struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
> >>> +       unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
> >>>         struct list_head wait_list;             /* store on-flushing entries */
> >>>         wait_queue_head_t discard_wait_queue;   /* waiting queue for wake-up */
> >>> +       unsigned int discard_wake;              /* to wake up discard thread */
> >>>         struct mutex cmd_lock;
> >>>         unsigned int nr_discards;               /* # of discards in the list */
> >>>         unsigned int max_discards;              /* max. discards to be issued */
> >>> +       unsigned int discard_granularity;       /* discard granularity */
> >>>         unsigned int undiscard_blks;            /* # of undiscard blocks */
> >>>         atomic_t issued_discard;                /* # of issued discard */
> >>>         atomic_t issing_discard;                /* # of issing discard */
> >>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> >>> index 05144b3a7f62..1387925a0d83 100644
> >>> --- a/fs/f2fs/segment.c
> >>> +++ b/fs/f2fs/segment.c
> >>> @@ -1016,32 +1016,65 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
> >>>         return 0;
> >>>  }
> >>>
> >>> -static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
> >>> +static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
> >>>  {
> >>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> >>>         struct list_head *pend_list;
> >>>         struct discard_cmd *dc, *tmp;
> >>>         struct blk_plug plug;
> >>> -       int i, iter = 0;
> >>> +       int iter = 0, issued = 0;
> >>> +       int i;
> >>>
> >>>         mutex_lock(&dcc->cmd_lock);
> >>>         f2fs_bug_on(sbi,
> >>>                 !__check_rb_tree_consistence(sbi, &dcc->root));
> >>>         blk_start_plug(&plug);
> >>> -       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> >>> +       for (i = MAX_PLIST_NUM - 1;
> >>> +                       i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
> >>>                 pend_list = &dcc->pend_list[i];
> >>>                 list_for_each_entry_safe(dc, tmp, pend_list, list) {
> >>>                         f2fs_bug_on(sbi, dc->state != D_PREP);
> >>>
> >>> -                       if (!issue_cond || is_idle(sbi))
> >>> +                       /* Hurry up to finish fstrim */
> >>> +                       if (dcc->pend_list_tag[i] & P_TRIM) {
> >>> +                               __submit_discard_cmd(sbi, dc);
> >>> +                               issued++;
> >>> +                               continue;
> >>> +                       }
> >>> +
> >>> +                       if (!issue_cond || is_idle(sbi)) {
> >>> +                               issued++;
> >>>                                 __submit_discard_cmd(sbi, dc);
> >>> +                       }
> >>>                         if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
> >>>                                 goto out;
> >>>                 }
> >>> +               if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
> >>> +                       dcc->pend_list_tag[i] &= (~P_TRIM);
> >>>         }
> >>>  out:
> >>>         blk_finish_plug(&plug);
> >>>         mutex_unlock(&dcc->cmd_lock);
> >>> +
> >>> +       return issued;
> >>> +}
> >>> +
> >>> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
> >>> +{
> >>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> >>> +       struct list_head *pend_list;
> >>> +       struct discard_cmd *dc, *tmp;
> >>> +       int i;
> >>> +
> >>> +       mutex_lock(&dcc->cmd_lock);
> >>> +       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> >>> +               pend_list = &dcc->pend_list[i];
> >>> +               list_for_each_entry_safe(dc, tmp, pend_list, list) {
> >>> +                       f2fs_bug_on(sbi, dc->state != D_PREP);
> >>> +                       __remove_discard_cmd(sbi, dc);
> >>> +               }
> >>> +       }
> >>> +       mutex_unlock(&dcc->cmd_lock);
> >>>  }
> >>>
> >>>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
> >>> @@ -1126,34 +1159,56 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
> >>>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
> >>>  {
> >>>         __issue_discard_cmd(sbi, false);
> >>> +       __drop_discard_cmd(sbi);
> >>>         __wait_discard_cmd(sbi, false);
> >>>  }
> >>>
> >>> +static void mark_discard_range_all(struct f2fs_sb_info *sbi)
> >>> +{
> >>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> >>> +       int i;
> >>> +
> >>> +       mutex_lock(&dcc->cmd_lock);
> >>> +       for (i = 0; i < MAX_PLIST_NUM; i++)
> >>> +               dcc->pend_list_tag[i] |= P_TRIM;
> >>> +       mutex_unlock(&dcc->cmd_lock);
> >>> +}
> >>> +
> >>>  static int issue_discard_thread(void *data)
> >>>  {
> >>>         struct f2fs_sb_info *sbi = data;
> >>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> >>>         wait_queue_head_t *q = &dcc->discard_wait_queue;
> >>> +       unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
> >>> +       int issued;
> >>>
> >>>         set_freezable();
> >>>
> >>>         do {
> >>> -               wait_event_interruptible(*q, kthread_should_stop() ||
> >>> -                                       freezing(current) ||
> >>> -                                       atomic_read(&dcc->discard_cmd_cnt));
> >>> +               wait_event_interruptible_timeout(*q,
> >>> +                               kthread_should_stop() || freezing(current) ||
> >>> +                               dcc->discard_wake,
> >>> +                               msecs_to_jiffies(wait_ms));
> >>>                 if (try_to_freeze())
> >>>                         continue;
> >>>                 if (kthread_should_stop())
> >>>                         return 0;
> >>>
> >>> +               if (dcc->discard_wake)
> >>> +                       dcc->discard_wake = 0;
> >>> +
> >>>                 sb_start_intwrite(sbi->sb);
> >>>
> >>> -               __issue_discard_cmd(sbi, true);
> >>> -               __wait_discard_cmd(sbi, true);
> >>> +               issued = __issue_discard_cmd(sbi, true);
> >>> +               if (issued) {
> >>> +                       __wait_discard_cmd(sbi, true);
> >>> +                       wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
> >>> +               } else {
> >>> +                       wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
> >>> +               }
> >>>
> >>>                 sb_end_intwrite(sbi->sb);
> >>>
> >>> -               congestion_wait(BLK_RW_SYNC, HZ/50);
> >>>         } while (!kthread_should_stop());
> >>>         return 0;
> >>>  }
> >>> @@ -1344,7 +1399,8 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
> >>>
> >>>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> >>>  {
> >>> -       struct list_head *head = &(SM_I(sbi)->dcc_info->entry_list);
> >>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> >>> +       struct list_head *head = &dcc->entry_list;
> >>>         struct discard_entry *entry, *this;
> >>>         struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> >>>         unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
> >>> @@ -1426,11 +1482,12 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> >>>                         goto find_next;
> >>>
> >>>                 list_del(&entry->list);
> >>> -               SM_I(sbi)->dcc_info->nr_discards -= total_len;
> >>> +               dcc->nr_discards -= total_len;
> >>>                 kmem_cache_free(discard_entry_slab, entry);
> >>>         }
> >>>
> >>> -       wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
> >>> +       dcc->discard_wake = 1;
> >>> +       wake_up_interruptible_all(&dcc->discard_wait_queue);
> >>>  }
> >>>
> >>>  static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
> >>> @@ -1448,9 +1505,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
> >>>         if (!dcc)
> >>>                 return -ENOMEM;
> >>>
> >>> +       dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
> >>>         INIT_LIST_HEAD(&dcc->entry_list);
> >>> -       for (i = 0; i < MAX_PLIST_NUM; i++)
> >>> +       for (i = 0; i < MAX_PLIST_NUM; i++) {
> >>>                 INIT_LIST_HEAD(&dcc->pend_list[i]);
> >>> +               if (i >= dcc->discard_granularity - 1)
> >>> +                       dcc->pend_list_tag[i] |= P_ACTIVE;
> >>> +       }
> >>>         INIT_LIST_HEAD(&dcc->wait_list);
> >>>         mutex_init(&dcc->cmd_lock);
> >>>         atomic_set(&dcc->issued_discard, 0);
> >>> @@ -2127,6 +2188,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
> >>>
> >>>                 schedule();
> >>>         }
> >>> +       /* It's time to issue all the filed discards */
> >>> +       mark_discard_range_all(sbi);
> >>>  out:
> >>>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
> >>>         return err;
> >>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> >>> index c40e5d24df9f..4bcaa9059026 100644
> >>> --- a/fs/f2fs/sysfs.c
> >>> +++ b/fs/f2fs/sysfs.c
> >>> @@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
> >>>                 spin_unlock(&sbi->stat_lock);
> >>>                 return count;
> >>>         }
> >>> +
> >>> +       if (!strcmp(a->attr.name, "discard_granularity")) {
> >>> +               struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> >>> +               int i;
> >>> +
> >>> +               if (t == 0 || t > MAX_PLIST_NUM)
> >>> +                       return -EINVAL;
> >>> +               if (t == *ui)
> >>> +                       return count;
> >>> +
> >>> +               mutex_lock(&dcc->cmd_lock);
> >>> +               for (i = 0; i < MAX_PLIST_NUM; i++) {
> >>> +                       if (i >= t - 1)
> >>> +                               dcc->pend_list_tag[i] |= P_ACTIVE;
> >>> +                       else
> >>> +                               dcc->pend_list_tag[i] &= (~P_ACTIVE);
> >>> +               }
> >>> +               mutex_unlock(&dcc->cmd_lock);
> >>> +               return count;
> >>> +       }
> >>> +
> >>>         *ui = t;
> >>>
> >>>         if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
> >>> @@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
> >>>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
> >>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
> >>>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
> >>> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
> >>>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
> >>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
> >>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
> >>> @@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
> >>>         ATTR_LIST(gc_urgent),
> >>>         ATTR_LIST(reclaim_segments),
> >>>         ATTR_LIST(max_small_discards),
> >>> +       ATTR_LIST(discard_granularity),
> >>>         ATTR_LIST(batched_trim_sections),
> >>>         ATTR_LIST(ipu_policy),
> >>>         ATTR_LIST(min_ipu_util),
> >>> --
> >>> 2.14.0.rc1.383.gd1ce394fe2-goog
> >>>
> >>>
> >>> ------------------------------------------------------------------------------
> >>> Check out the vibrant tech community on one of the world's most
> >>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> >>> _______________________________________________
> >>> Linux-f2fs-devel mailing list
> >>> Linux-f2fs-devel@lists.sourceforge.net
> >>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [f2fs-dev] [PATCH v4] f2fs: introduce discard_granularity sysfs entry

[Chao Yu]

Hi Ju Hyung, Jaegeuk,

On 2017/10/4 4:17, Jaegeuk Kim wrote:
> On 10/04, Ju Hyung Park wrote:
>> Hi Chao.
>>
>> Yep, that patch seems to have fixed it.
>> Doing "while true; do fstrim -v /; done" while "rm -rf"ing a 2GB
>> kbuild directory
>> (with lots of small .o files and stuff) ended flawlessly.

Thanks for the test. ;)

>>
>> I hope to see this patch merged with next 4.14 merge cycle.
> 
> Cool! I'll merge this patch and submit for 4.14. :)

Thanks for the quick merging. ;)

Thanks,

> 
> Thanks,
> 
>>
>> Thanks :)
>>
>> On Tue, Oct 3, 2017 at 12:59 AM, Chao Yu <chao@kernel.org> wrote:
>>> Hi Park,
>>>
>>> Thanks for the report, could have a try with below patch:
>>>
>>> From 5fa30e8cdcb93f210e25142c48a884be383c6121 Mon Sep 17 00:00:00 2001
>>> From: Chao Yu <yuchao0@huawei.com>
>>> Date: Mon, 2 Oct 2017 02:50:16 +0800
>>> Subject: [PATCH] f2fs: fix potential panic during fstrim
>>>
>>> As Ju Hyung Park reported:
>>>
>>> "When 'fstrim' is called for manual trim, a BUG() can be triggered
>>> randomly with this patch.
>>>
>>> I'm seeing this issue on both x86 Desktop and arm64 Android phone.
>>>
>>> On x86 Desktop, this was caused during Ubuntu boot-up. I have a
>>> cronjob installed which calls 'fstrim -v /' during boot. On arm64
>>> Android, this was caused during GC looping with 1ms gc_min_sleep_time
>>> & gc_max_sleep_time."
>>>
>>> Root cause of this issue is that f2fs_wait_discard_bios can only be
>>> used by f2fs_put_super, because during put_super there must be no
>>> other referrers, so it can ignore discard entry's reference count
>>> when removing the entry, otherwise in other caller we will hit bug_on
>>> in __remove_discard_cmd as there may be other issuer added reference
>>> count in discard entry.
>>>
>>> Thread A                                Thread B
>>>                                         - issue_discard_thread
>>> - f2fs_ioc_fitrim
>>>  - f2fs_trim_fs
>>>   - f2fs_wait_discard_bios
>>>    - __issue_discard_cmd
>>>     - __submit_discard_cmd
>>>                                          - __wait_discard_cmd
>>>                                           - dc->ref++
>>>                                           - __wait_one_discard_bio
>>>    - __wait_discard_cmd
>>>     - __remove_discard_cmd
>>>      - f2fs_bug_on(sbi, dc->ref)
>>>
>>> Fixes: 969d1b180d987c2be02de890d0fff0f66a0e80de
>>> Reported-by: Ju Hyung Park <qkrwngud825@gmail.com>
>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>> ---
>>>  fs/f2fs/f2fs.h    | 2 +-
>>>  fs/f2fs/segment.c | 6 +++---
>>>  fs/f2fs/super.c   | 2 +-
>>>  3 files changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 9a7c90386947..4b4a72f392be 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -2525,7 +2525,7 @@ void invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr);
>>>  bool is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
>>>  void refresh_sit_entry(struct f2fs_sb_info *sbi, block_t old, block_t new);
>>>  void stop_discard_thread(struct f2fs_sb_info *sbi);
>>> -void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi);
>>> +void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount);
>>>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc);
>>>  void release_discard_addrs(struct f2fs_sb_info *sbi);
>>>  int npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index dedf0209d820..e28245b7e44e 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -1210,11 +1210,11 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>>>  }
>>>
>>>  /* This comes from f2fs_put_super and f2fs_trim_fs */
>>> -void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>>> +void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi, bool umount)
>>>  {
>>>         __issue_discard_cmd(sbi, false);
>>>         __drop_discard_cmd(sbi);
>>> -       __wait_discard_cmd(sbi, false);
>>> +       __wait_discard_cmd(sbi, !umount);
>>>  }
>>>
>>>  static void mark_discard_range_all(struct f2fs_sb_info *sbi)
>>> @@ -2244,7 +2244,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>>>         }
>>>         /* It's time to issue all the filed discards */
>>>         mark_discard_range_all(sbi);
>>> -       f2fs_wait_discard_bios(sbi);
>>> +       f2fs_wait_discard_bios(sbi, false);
>>>  out:
>>>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>>>         return err;
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index 89f61eb3d167..933c3d529e65 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -801,7 +801,7 @@ static void f2fs_put_super(struct super_block *sb)
>>>         }
>>>
>>>         /* be sure to wait for any on-going discard commands */
>>> -       f2fs_wait_discard_bios(sbi);
>>> +       f2fs_wait_discard_bios(sbi, true);
>>>
>>>         if (f2fs_discard_en(sbi) && !sbi->discard_blks) {
>>>                 struct cp_control cpc = {
>>> --
>>> 2.14.1.145.gb3622a4ee
>>>
>>> On 2017/10/2 3:29, Ju Hyung Park wrote:
>>>> When 'fstrim' is called for manual trim, a BUG() can be triggered
>>>> randomly with this patch.
>>>>
>>>> I'm seeing this issue on both x86 Desktop and arm64 Android phone.
>>>>
>>>> On x86 Desktop, this was caused during Ubuntu boot-up. I have a
>>>> cronjob installed
>>>> which calls 'fstrim -v /' during boot.
>>>> On arm64 Android, this was caused during GC looping with
>>>> 1ms gc_min_sleep_time & gc_max_sleep_time.
>>>>
>>>> Thanks.
>>>>
>>>> [26671.666421] ------------[ cut here ]------------
>>>> [26671.666426] WARNING: CPU: 8 PID: 103479 at fs/f2fs/segment.c:797
>>>> __remove_discard_cmd+0xb9/0xd0
>>>> [26671.666427] Modules linked in: ftdi_sio usbserial uas usb_storage
>>>> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
>>>> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
>>>> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
>>>> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
>>>> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
>>>> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
>>>> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
>>>> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
>>>> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
>>>> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
>>>> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
>>>> snd_seq_device
>>>> [26671.666450]  snd_timer snd soundcore k10temp i2c_piix4
>>>> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
>>>> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
>>>> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
>>>> async_pq async_xor async_tx raid1 multipath linear hid_generic
>>>> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
>>>> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
>>>> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
>>>> [26671.666471] CPU: 8 PID: 103479 Comm: fstrim Tainted: P           O
>>>>   4.13.4-zen+ #1
>>>> [26671.666472] Hardware name: System manufacturer System Product
>>>> Name/PRIME X399-A, BIOS 0318 08/11/2017
>>>> [26671.666472] task: ffff8804ad535800 task.stack: ffff88047ee38000
>>>> [26671.666474] RIP: 0010:__remove_discard_cmd+0xb9/0xd0
>>>> [26671.666474] RSP: 0018:ffff88047ee3bd00 EFLAGS: 00010202
>>>> [26671.666475] RAX: ffff88081801a500 RBX: ffff88047eeaed00 RCX: ffff88047eeaedf8
>>>> [26671.666475] RDX: 0000000000000001 RSI: ffff88047eeaed00 RDI: ffff880802555800
>>>> [26671.666476] RBP: ffff8808134d0000 R08: ffff8804ad535800 R09: 0000000000000001
>>>> [26671.666476] R10: ffff88047ee3bd18 R11: 0000000000000000 R12: ffff880802555800
>>>> [26671.666476] R13: 0000000000000000 R14: ffff88047eeaedd0 R15: ffff8808134d0000
>>>> [26671.666477] FS:  00007f44cddad2c0(0000) GS:ffff88081ca00000(0000)
>>>> knlGS:0000000000000000
>>>> [26671.666478] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [26671.666478] CR2: 00007f88f5776328 CR3: 000000058ce4a000 CR4: 00000000003406e0
>>>> [26671.666479] Call Trace:
>>>> [26671.666481]  ? __wait_discard_cmd+0x7a/0xc0
>>>> [26671.666482]  ? f2fs_trim_fs+0x1c1/0x210
>>>> [26671.666484]  ? f2fs_ioctl+0x75a/0x2320
>>>> [26671.666486]  ? do_filp_open+0x99/0xe0
>>>> [26671.666487]  ? cp_new_stat+0x138/0x150
>>>> [26671.666489]  ? do_vfs_ioctl+0x88/0x5c0
>>>> [26671.666490]  ? SyS_newfstat+0x29/0x40
>>>> [26671.666491]  ? SyS_ioctl+0x6f/0x80
>>>> [26671.666493]  ? entry_SYSCALL_64_fastpath+0x1e/0xa9
>>>> [26671.666493] Code: 48 89 de 8b 43 1c 48 8b 3d 4d 8c 31 01 29 85 74
>>>> 22 00 00 e8 fa 01 d5 ff f0 ff 8d 80 22 00 00 5b 5d c3 c7 43 64 00 00
>>>> 00 00 eb 92 <0f> ff f0 80 4f 20 04 e9 53 ff ff ff 90 66 2e 0f 1f 84 00
>>>> 00 00
>>>> [26671.666506] ---[ end trace 613553f7a4728b5a ]---
>>>> [26672.553742] general protection fault: 0000 [#1] PREEMPT SMP
>>>> [26672.553746] Modules linked in: ftdi_sio usbserial uas usb_storage
>>>> vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) rfcomm
>>>> xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4
>>>> iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
>>>> xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge
>>>> stp llc bnep ebtable_filter ebtables ip6table_filter ip6_tables
>>>> xt_multiport iptable_filter binfmt_misc snd_hda_codec_hdmi eeepc_wmi
>>>> asus_wmi sparse_keymap video wmi_bmof mxm_wmi nls_iso8859_1 btusb
>>>> btrtl joydev btbcm btintel input_leds bluetooth edac_mce_amd
>>>> snd_hda_codec_realtek snd_hda_codec_generic kvm_amd kvm irqbypass
>>>> snd_seq_dummy snd_hda_intel snd_hda_codec snd_seq_oss snd_seq_midi
>>>> snd_hda_core snd_seq_midi_event snd_hwdep snd_pcm snd_rawmidi snd_seq
>>>> snd_seq_device
>>>> [26672.553771]  snd_timer snd soundcore k10temp i2c_piix4
>>>> nvidia_uvm(PO) shpchp wmi 8250_dw mac_hid parport_pc ppdev nfsd lp
>>>> auth_rpcgss parport oid_registry nfs_acl lockd grace sunrpc ip_tables
>>>> x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy
>>>> async_pq async_xor async_tx raid1 multipath linear hid_generic
>>>> hid_apple usbhid nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO)
>>>> drm_kms_helper syscopyarea sysfillrect sysimgblt igb fb_sys_fops dca
>>>> ptp drm pps_core i2c_algo_bit ahci libahci gpio_amdpt gpio_generic
>>>> [26672.553792] CPU: 10 PID: 1287 Comm: f2fs_discard-25 Tainted: P
>>>>   W  O    4.13.4-zen+ #1
>>>> [26672.553793] Hardware name: System manufacturer System Product
>>>> Name/PRIME X399-A, BIOS 0318 08/11/2017
>>>> [26672.553794] task: ffff8808159c1600 task.stack: ffff880813304000
>>>> [26672.553798] RIP: 0010:__remove_discard_cmd+0x6a/0xd0
>>>> [26672.553799] RSP: 0018:ffff880813307e20 EFLAGS: 00010296
>>>> [26672.553800] RAX: dead000000000200 RBX: ffff88047eeaed00 RCX: ffff8808159c1601
>>>> [26672.553801] RDX: dead000000000100 RSI: ffff8808134d2288 RDI: ffff88047eeaed00
>>>> [26672.553801] RBP: ffff8808134d0000 R08: 0000184230172c00 R09: 0000000000000006
>>>> [26672.553802] R10: ffff880813307e38 R11: 0000000000000023 R12: ffff880802555800
>>>> [26672.553803] R13: 0000000000000001 R14: ffff88047eeaed00 R15: ffff8808134d0000
>>>> [26672.553804] FS:  0000000000000000(0000) GS:ffff88081ca80000(0000)
>>>> knlGS:0000000000000000
>>>> [26672.553805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [26672.553805] CR2: 00007f88f2f71328 CR3: 000000048be79000 CR4: 00000000003406e0
>>>> [26672.553806] Call Trace:
>>>> [26672.553808]  ? __wait_one_discard_bio+0x41/0x60
>>>> [26672.553809]  ? __wait_discard_cmd+0xbb/0xc0
>>>> [26672.553811]  ? issue_discard_thread+0x196/0x200
>>>> [26672.553813]  ? wait_woken+0x80/0x80
>>>> [26672.553814]  ? mark_discard_range_all.isra.11+0x40/0x40
>>>> [26672.553816]  ? kthread+0x112/0x130
>>>> [26672.553817]  ? kthread_create_on_node+0x40/0x40
>>>> [26672.553818]  ? do_group_exit+0x2e/0xa0
>>>> [26672.553820]  ? ret_from_fork+0x25/0x30
>>>> [26672.553821] Code: 8b 43 20 48 8b 3f e8 56 6c fe ff 58 80 7b 62 02
>>>> 75 07 f0 ff 8d 7c 22 00 00 48 8b 53 28 48 8b 43 30 48 8d b5 88 22 00
>>>> 00 48 89 df <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89
>>>> 43 28
>>>> [26672.553835] RIP: __remove_discard_cmd+0x6a/0xd0 RSP: ffff880813307e20
>>>> [26672.553836] ---[ end trace 613553f7a4728b5b ]---
>>>>
>>>> On Tue, Aug 22, 2017 at 5:42 AM, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
>>>>> On 08/18, Chao Yu wrote:
>>>>>> Hi Jaegeuk,
>>>>>>
>>>>>> Sorry for the delay, the modification looks good to me. ;)
>>>>>
>>>>> We must avoid waking up discard thread caused by # of pending commands
>>>>> which are never issued.
>>>>>
>>>>> From a73f8807248c2f42328a2204eab16a3b8d32c83e Mon Sep 17 00:00:00 2001
>>>>> From: Chao Yu <yuchao0@huawei.com>
>>>>> Date: Mon, 7 Aug 2017 23:09:56 +0800
>>>>> Subject: [PATCH] f2fs: introduce discard_granularity sysfs entry
>>>>>
>>>>> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables
>>>>> f2fs to issue 4K size discard in real-time discard mode. However, issuing
>>>>> smaller discard may cost more lifetime but releasing less free space in
>>>>> flash device. Since f2fs has ability of separating hot/cold data and
>>>>> garbage collection, we can expect that small-sized invalid region would
>>>>> expand soon with OPU, deletion or garbage collection on valid datas, so
>>>>> it's better to delay or skip issuing smaller size discards, it could help
>>>>> to reduce overmuch consumption of IO bandwidth and lifetime of flash
>>>>> storage.
>>>>>
>>>>> This patch makes f2fs selectng 64K size as its default minimal
>>>>> granularity, and issue discard with the size which is not smaller than
>>>>> minimal granularity. Also it exposes discard granularity as sysfs entry
>>>>> for configuration in different scenario.
>>>>>
>>>>> Jaegeuk Kim:
>>>>>  We must issue all the accumulated discard commands when fstrim is called.
>>>>>  So, I've added pend_list_tag[] to indicate whether we should issue the
>>>>>  commands or not. If tag sets P_ACTIVE or P_TRIM, we have to issue them.
>>>>>  P_TRIM is set once at a time, given fstrim trigger.
>>>>>  In addition, issue_discard_thread is calling too much due to the number of
>>>>>  discard commands remaining in the pending list. I added a timer to control
>>>>>  it likewise gc_thread.
>>>>>
>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>>>> ---
>>>>>  Documentation/ABI/testing/sysfs-fs-f2fs |  9 ++++
>>>>>  fs/f2fs/f2fs.h                          | 12 +++++
>>>>>  fs/f2fs/segment.c                       | 91 ++++++++++++++++++++++++++++-----
>>>>>  fs/f2fs/sysfs.c                         | 23 +++++++++
>>>>>  4 files changed, 121 insertions(+), 14 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>>> index 621da3fc56c5..11b7f4ebea7c 100644
>>>>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>>>>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>>> @@ -57,6 +57,15 @@ Contact:     "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>>>>>  Description:
>>>>>                  Controls the issue rate of small discard commands.
>>>>>
>>>>> +What:          /sys/fs/f2fs/<disk>/discard_granularity
>>>>> +Date:          July 2017
>>>>> +Contact:       "Chao Yu" <yuchao0@huawei.com>
>>>>> +Description:
>>>>> +               Controls discard granularity of inner discard thread, inner thread
>>>>> +               will not issue discards with size that is smaller than granularity.
>>>>> +               The unit size is one block, now only support configuring in range
>>>>> +               of [1, 512].
>>>>> +
>>>>>  What:          /sys/fs/f2fs/<disk>/max_victim_search
>>>>>  Date:          January 2014
>>>>>  Contact:       "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index e252e5bf9791..4b993961d81d 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -148,6 +148,8 @@ enum {
>>>>>                 (BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
>>>>>  #define MAX_DISCARD_BLOCKS(sbi)                BLKS_PER_SEC(sbi)
>>>>>  #define DISCARD_ISSUE_RATE             8
>>>>> +#define DEF_MIN_DISCARD_ISSUE_TIME     50      /* 50 ms, if exists */
>>>>> +#define DEF_MAX_DISCARD_ISSUE_TIME     60000   /* 60 s, if no candidates */
>>>>>  #define DEF_CP_INTERVAL                        60      /* 60 secs */
>>>>>  #define DEF_IDLE_INTERVAL              5       /* 5 secs */
>>>>>
>>>>> @@ -196,11 +198,18 @@ struct discard_entry {
>>>>>         unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard bitmap */
>>>>>  };
>>>>>
>>>>> +/* default discard granularity of inner discard thread, unit: block count */
>>>>> +#define DEFAULT_DISCARD_GRANULARITY            16
>>>>> +
>>>>>  /* max discard pend list number */
>>>>>  #define MAX_PLIST_NUM          512
>>>>>  #define plist_idx(blk_num)     ((blk_num) >= MAX_PLIST_NUM ?           \
>>>>>                                         (MAX_PLIST_NUM - 1) : (blk_num - 1))
>>>>>
>>>>> +#define P_ACTIVE       0x01
>>>>> +#define P_TRIM         0x02
>>>>> +#define plist_issue(tag)       (((tag) & P_ACTIVE) || ((tag) & P_TRIM))
>>>>> +
>>>>>  enum {
>>>>>         D_PREP,
>>>>>         D_SUBMIT,
>>>>> @@ -236,11 +245,14 @@ struct discard_cmd_control {
>>>>>         struct task_struct *f2fs_issue_discard; /* discard thread */
>>>>>         struct list_head entry_list;            /* 4KB discard entry list */
>>>>>         struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
>>>>> +       unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
>>>>>         struct list_head wait_list;             /* store on-flushing entries */
>>>>>         wait_queue_head_t discard_wait_queue;   /* waiting queue for wake-up */
>>>>> +       unsigned int discard_wake;              /* to wake up discard thread */
>>>>>         struct mutex cmd_lock;
>>>>>         unsigned int nr_discards;               /* # of discards in the list */
>>>>>         unsigned int max_discards;              /* max. discards to be issued */
>>>>> +       unsigned int discard_granularity;       /* discard granularity */
>>>>>         unsigned int undiscard_blks;            /* # of undiscard blocks */
>>>>>         atomic_t issued_discard;                /* # of issued discard */
>>>>>         atomic_t issing_discard;                /* # of issing discard */
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 05144b3a7f62..1387925a0d83 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -1016,32 +1016,65 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>         return 0;
>>>>>  }
>>>>>
>>>>> -static void __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>>>> +static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>>>>>  {
>>>>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>>         struct list_head *pend_list;
>>>>>         struct discard_cmd *dc, *tmp;
>>>>>         struct blk_plug plug;
>>>>> -       int i, iter = 0;
>>>>> +       int iter = 0, issued = 0;
>>>>> +       int i;
>>>>>
>>>>>         mutex_lock(&dcc->cmd_lock);
>>>>>         f2fs_bug_on(sbi,
>>>>>                 !__check_rb_tree_consistence(sbi, &dcc->root));
>>>>>         blk_start_plug(&plug);
>>>>> -       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>>>>> +       for (i = MAX_PLIST_NUM - 1;
>>>>> +                       i >= 0 && plist_issue(dcc->pend_list_tag[i]); i--) {
>>>>>                 pend_list = &dcc->pend_list[i];
>>>>>                 list_for_each_entry_safe(dc, tmp, pend_list, list) {
>>>>>                         f2fs_bug_on(sbi, dc->state != D_PREP);
>>>>>
>>>>> -                       if (!issue_cond || is_idle(sbi))
>>>>> +                       /* Hurry up to finish fstrim */
>>>>> +                       if (dcc->pend_list_tag[i] & P_TRIM) {
>>>>> +                               __submit_discard_cmd(sbi, dc);
>>>>> +                               issued++;
>>>>> +                               continue;
>>>>> +                       }
>>>>> +
>>>>> +                       if (!issue_cond || is_idle(sbi)) {
>>>>> +                               issued++;
>>>>>                                 __submit_discard_cmd(sbi, dc);
>>>>> +                       }
>>>>>                         if (issue_cond && iter++ > DISCARD_ISSUE_RATE)
>>>>>                                 goto out;
>>>>>                 }
>>>>> +               if (list_empty(pend_list) && dcc->pend_list_tag[i] & P_TRIM)
>>>>> +                       dcc->pend_list_tag[i] &= (~P_TRIM);
>>>>>         }
>>>>>  out:
>>>>>         blk_finish_plug(&plug);
>>>>>         mutex_unlock(&dcc->cmd_lock);
>>>>> +
>>>>> +       return issued;
>>>>> +}
>>>>> +
>>>>> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi)
>>>>> +{
>>>>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>> +       struct list_head *pend_list;
>>>>> +       struct discard_cmd *dc, *tmp;
>>>>> +       int i;
>>>>> +
>>>>> +       mutex_lock(&dcc->cmd_lock);
>>>>> +       for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>>>>> +               pend_list = &dcc->pend_list[i];
>>>>> +               list_for_each_entry_safe(dc, tmp, pend_list, list) {
>>>>> +                       f2fs_bug_on(sbi, dc->state != D_PREP);
>>>>> +                       __remove_discard_cmd(sbi, dc);
>>>>> +               }
>>>>> +       }
>>>>> +       mutex_unlock(&dcc->cmd_lock);
>>>>>  }
>>>>>
>>>>>  static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>>>>> @@ -1126,34 +1159,56 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>>>>>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>>>>>  {
>>>>>         __issue_discard_cmd(sbi, false);
>>>>> +       __drop_discard_cmd(sbi);
>>>>>         __wait_discard_cmd(sbi, false);
>>>>>  }
>>>>>
>>>>> +static void mark_discard_range_all(struct f2fs_sb_info *sbi)
>>>>> +{
>>>>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>> +       int i;
>>>>> +
>>>>> +       mutex_lock(&dcc->cmd_lock);
>>>>> +       for (i = 0; i < MAX_PLIST_NUM; i++)
>>>>> +               dcc->pend_list_tag[i] |= P_TRIM;
>>>>> +       mutex_unlock(&dcc->cmd_lock);
>>>>> +}
>>>>> +
>>>>>  static int issue_discard_thread(void *data)
>>>>>  {
>>>>>         struct f2fs_sb_info *sbi = data;
>>>>>         struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>>         wait_queue_head_t *q = &dcc->discard_wait_queue;
>>>>> +       unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>> +       int issued;
>>>>>
>>>>>         set_freezable();
>>>>>
>>>>>         do {
>>>>> -               wait_event_interruptible(*q, kthread_should_stop() ||
>>>>> -                                       freezing(current) ||
>>>>> -                                       atomic_read(&dcc->discard_cmd_cnt));
>>>>> +               wait_event_interruptible_timeout(*q,
>>>>> +                               kthread_should_stop() || freezing(current) ||
>>>>> +                               dcc->discard_wake,
>>>>> +                               msecs_to_jiffies(wait_ms));
>>>>>                 if (try_to_freeze())
>>>>>                         continue;
>>>>>                 if (kthread_should_stop())
>>>>>                         return 0;
>>>>>
>>>>> +               if (dcc->discard_wake)
>>>>> +                       dcc->discard_wake = 0;
>>>>> +
>>>>>                 sb_start_intwrite(sbi->sb);
>>>>>
>>>>> -               __issue_discard_cmd(sbi, true);
>>>>> -               __wait_discard_cmd(sbi, true);
>>>>> +               issued = __issue_discard_cmd(sbi, true);
>>>>> +               if (issued) {
>>>>> +                       __wait_discard_cmd(sbi, true);
>>>>> +                       wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>> +               } else {
>>>>> +                       wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
>>>>> +               }
>>>>>
>>>>>                 sb_end_intwrite(sbi->sb);
>>>>>
>>>>> -               congestion_wait(BLK_RW_SYNC, HZ/50);
>>>>>         } while (!kthread_should_stop());
>>>>>         return 0;
>>>>>  }
>>>>> @@ -1344,7 +1399,8 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)
>>>>>
>>>>>  void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>  {
>>>>> -       struct list_head *head = &(SM_I(sbi)->dcc_info->entry_list);
>>>>> +       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>> +       struct list_head *head = &dcc->entry_list;
>>>>>         struct discard_entry *entry, *this;
>>>>>         struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
>>>>>         unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
>>>>> @@ -1426,11 +1482,12 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>                         goto find_next;
>>>>>
>>>>>                 list_del(&entry->list);
>>>>> -               SM_I(sbi)->dcc_info->nr_discards -= total_len;
>>>>> +               dcc->nr_discards -= total_len;
>>>>>                 kmem_cache_free(discard_entry_slab, entry);
>>>>>         }
>>>>>
>>>>> -       wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
>>>>> +       dcc->discard_wake = 1;
>>>>> +       wake_up_interruptible_all(&dcc->discard_wait_queue);
>>>>>  }
>>>>>
>>>>>  static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>>>> @@ -1448,9 +1505,13 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>>>>         if (!dcc)
>>>>>                 return -ENOMEM;
>>>>>
>>>>> +       dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>>>>>         INIT_LIST_HEAD(&dcc->entry_list);
>>>>> -       for (i = 0; i < MAX_PLIST_NUM; i++)
>>>>> +       for (i = 0; i < MAX_PLIST_NUM; i++) {
>>>>>                 INIT_LIST_HEAD(&dcc->pend_list[i]);
>>>>> +               if (i >= dcc->discard_granularity - 1)
>>>>> +                       dcc->pend_list_tag[i] |= P_ACTIVE;
>>>>> +       }
>>>>>         INIT_LIST_HEAD(&dcc->wait_list);
>>>>>         mutex_init(&dcc->cmd_lock);
>>>>>         atomic_set(&dcc->issued_discard, 0);
>>>>> @@ -2127,6 +2188,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>>>>>
>>>>>                 schedule();
>>>>>         }
>>>>> +       /* It's time to issue all the filed discards */
>>>>> +       mark_discard_range_all(sbi);
>>>>>  out:
>>>>>         range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>>>>>         return err;
>>>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>>>> index c40e5d24df9f..4bcaa9059026 100644
>>>>> --- a/fs/f2fs/sysfs.c
>>>>> +++ b/fs/f2fs/sysfs.c
>>>>> @@ -152,6 +152,27 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>>>>                 spin_unlock(&sbi->stat_lock);
>>>>>                 return count;
>>>>>         }
>>>>> +
>>>>> +       if (!strcmp(a->attr.name, "discard_granularity")) {
>>>>> +               struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>> +               int i;
>>>>> +
>>>>> +               if (t == 0 || t > MAX_PLIST_NUM)
>>>>> +                       return -EINVAL;
>>>>> +               if (t == *ui)
>>>>> +                       return count;
>>>>> +
>>>>> +               mutex_lock(&dcc->cmd_lock);
>>>>> +               for (i = 0; i < MAX_PLIST_NUM; i++) {
>>>>> +                       if (i >= t - 1)
>>>>> +                               dcc->pend_list_tag[i] |= P_ACTIVE;
>>>>> +                       else
>>>>> +                               dcc->pend_list_tag[i] &= (~P_ACTIVE);
>>>>> +               }
>>>>> +               mutex_unlock(&dcc->cmd_lock);
>>>>> +               return count;
>>>>> +       }
>>>>> +
>>>>>         *ui = t;
>>>>>
>>>>>         if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
>>>>> @@ -248,6 +269,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
>>>>>  F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
>>>>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
>>>>>  F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
>>>>> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
>>>>>  F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
>>>>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>>>>>  F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
>>>>> @@ -290,6 +312,7 @@ static struct attribute *f2fs_attrs[] = {
>>>>>         ATTR_LIST(gc_urgent),
>>>>>         ATTR_LIST(reclaim_segments),
>>>>>         ATTR_LIST(max_small_discards),
>>>>> +       ATTR_LIST(discard_granularity),
>>>>>         ATTR_LIST(batched_trim_sections),
>>>>>         ATTR_LIST(ipu_policy),
>>>>>         ATTR_LIST(min_ipu_util),
>>>>> --
>>>>> 2.14.0.rc1.383.gd1ce394fe2-goog
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> Check out the vibrant tech community on one of the world's most
>>>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>>>> _______________________________________________
>>>>> Linux-f2fs-devel mailing list
>>>>> Linux-f2fs-devel@lists.sourceforge.net
>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> 
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