Re: [f2fs-dev] Writes stoped working on f2fs after the compression support was added

[Chao Yu <yuchao0@huawei.com>]

On 2020/2/25 20:27, Ondřej Jirman wrote:
> On Tue, Feb 25, 2020 at 01:08:14PM +0100, megi xff wrote:
>> Hello,
>>
>> On Tue, Feb 25, 2020 at 07:24:12PM +0800, Chao Yu wrote:
>>> On 2020/2/24 22:31, Ondřej Jirman wrote:
>>>>> Just by a looks of it:
>>>>>
>>>>> root@tbs2[/proc/sys/kernel] # dmesg | grep up_write | wc -l
>>>>> 324
>>>>> root@tbs2[/proc/sys/kernel] # dmesg | grep down_write | wc -l
>>>>> 347
>>>>>
>>>>> there seems to be a mismatch of lock/unlock counts.
>>>>  
>>>> Sorry, a wrong grep expression.
>>>>
>>>> root@tbs2[~] # dmesg | grep inode_down_write | wc -l
>>>> 357
>>>> root@tbs2[~] # dmesg | grep inode_up_write | wc -l
>>>> 357
>>>> root@tbs2[~] # dmesg | grep inode_up_read | wc -l
>>>> 16
>>>> root@tbs2[~] # dmesg | grep inode_down_read | wc -l
>>>> 16
>>>
>>> I don't know why we have consistent down/up pair, but through disassembled
>>> code, I doubt it's the f2fs_inode->i_sem.
>>
>> Because we were counting attempts, and not a successful lock. ;)

[  214.508943] inode_down_write from f2fs_write_cache_pages+0x2b4/0x7c4
[  306.213325] inode_down_write from f2fs_write_cache_pages+0x2b4/0x7c4

Actually, down_write count is 320, up_write count is 319, kworker didn't call
up_write at 214.508943.

>>
>>> c0435d7c:       ebf54af8        bl      c0188964 <printk>
>>> c0435d80:       e1a00006        mov     r0, r6
>>> c0435d84:       eb138135        bl      c0916260 <down_write>
>>>
>>> inode_down_write()
>>>
>>> c0435d88:       e284ce1d        add     ip, r4, #464    ; 0x1d0
>>>
>>> We are stuck here.
>>>
>>> [  430.675754] [<c0916260>] (down_write) from [<c0435d88>] (f2fs_write_single_data_page+0x600/0x7d8)
>>>                                                 ^^^^^^^^^
>>> [  430.675764] [<c0435788>] (f2fs_write_single_data_page) from [<c0436214>] (f2fs_write_cache_pages+0x2b4/0x7c4)
>>>
>>>
>>> c0435d8c:       e14b0ad4        ldrd    r0, [fp, #-164] ; 0xffffff5c
>>> c0435d90:       e1cc20d0        ldrd    r2, [ip]
>>> c0435d94:       e1520000        cmp     r2, r0
>>> c0435d98:       e0d33001        sbcs    r3, r3, r1
>>> c0435d9c:       b1cc00f0        strdlt  r0, [ip]
>>> c0435da0:       e1a00006        mov     r0, r6
>>> c0435da4:       ebf52227        bl      c017e648 <up_write>
>>> c0435da8:       e51b2098        ldr     r2, [fp, #-152] ; 0xffffff68
>>> c0435dac:       e30c0730        movw    r0, #50992      ; 0xc730
>>> c0435db0:       e59f11a4        ldr     r1, [pc, #420]  ; c0435f5c <f2fs_write_single_data_page+0x7d4>
>>> c0435db4:       e34c00b6        movt    r0, #49334      ; 0xc0b6
>>> c0435db8:       ebf54ae9        bl      c0188964 <printk>
>>>
>>> inode_up_write()
>>
>> The patch you sent helped so far. I'll keep the tablet running for a while,
>> but so far the issue did not reappear within a few minutes after boot as
>> usual.
> 
> So this time it just took several times longer to appear (8-20mins to the hang):
> 
> https://megous.com/dl/tmp/dmesg1
> https://megous.com/dl/tmp/dmesg2

Alright, I still didn't see any possible deadlock in f2fs.

Can you try below patch? I'd like to see whether spinlock can cause the same issue.

From 3e9e8daf922eaa2c5db195ce278e89e10191c516 Mon Sep 17 00:00:00 2001
From: Chao Yu <yuchao0@huawei.com>
Date: Wed, 26 Feb 2020 09:53:03 +0800
Subject: [PATCH] fix

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
 fs/f2fs/compress.c | 4 ++--
 fs/f2fs/data.c     | 4 ++--
 fs/f2fs/f2fs.h     | 5 +++--
 fs/f2fs/file.c     | 4 ++--
 fs/f2fs/super.c    | 1 +
 5 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index b4ff25dc55a9..6de0872ad881 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -906,10 +906,10 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
 	f2fs_put_dnode(&dn);
 	f2fs_unlock_op(sbi);

-	down_write(&fi->i_sem);
+	spin_lock(&fi->i_size_lock);
 	if (fi->last_disk_size < psize)
 		fi->last_disk_size = psize;
-	up_write(&fi->i_sem);
+	spin_unlock(&fi->i_size_lock);

 	f2fs_put_rpages(cc);
 	f2fs_destroy_compress_ctx(cc);
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index cb41260ca941..5c9b072cf0de 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2651,10 +2651,10 @@ int f2fs_write_single_data_page(struct page *page, int *submitted,
 	if (err) {
 		file_set_keep_isize(inode);
 	} else {
-		down_write(&F2FS_I(inode)->i_sem);
+		spin_lock(&F2FS_I(inode)->i_size_lock);
 		if (F2FS_I(inode)->last_disk_size < psize)
 			F2FS_I(inode)->last_disk_size = psize;
-		up_write(&F2FS_I(inode)->i_sem);
+		spin_unlock(&F2FS_I(inode)->i_size_lock);
 	}

 done:
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4a02edc2454b..1a8af2020e72 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -701,6 +701,7 @@ struct f2fs_inode_info {
 	struct task_struct *cp_task;	/* separate cp/wb IO stats*/
 	nid_t i_xattr_nid;		/* node id that contains xattrs */
 	loff_t	last_disk_size;		/* lastly written file size */
+	spinlock_t i_size_lock;		/* protect last_disk_size */

 #ifdef CONFIG_QUOTA
 	struct dquot *i_dquot[MAXQUOTAS];
@@ -2882,9 +2883,9 @@ static inline bool f2fs_skip_inode_update(struct inode *inode, int dsync)
 	if (!f2fs_is_time_consistent(inode))
 		return false;

-	down_read(&F2FS_I(inode)->i_sem);
+	spin_lock(&F2FS_I(inode)->i_size_lock);
 	ret = F2FS_I(inode)->last_disk_size == i_size_read(inode);
-	up_read(&F2FS_I(inode)->i_sem);
+	spin_unlock(&F2FS_I(inode)->i_size_lock);

 	return ret;
 }
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index fdb492c2f248..56fe18fbb2ef 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -938,10 +938,10 @@ int f2fs_setattr(struct dentry *dentry, struct iattr *attr)
 		if (err)
 			return err;

-		down_write(&F2FS_I(inode)->i_sem);
+		spin_lock(&F2FS_I(inode)->i_size_lock);
 		inode->i_mtime = inode->i_ctime = current_time(inode);
 		F2FS_I(inode)->last_disk_size = i_size_read(inode);
-		up_write(&F2FS_I(inode)->i_sem);
+		spin_unlock(&F2FS_I(inode)->i_size_lock);
 	}

 	__setattr_copy(inode, attr);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 0b16204d3b7d..2d0e5d1269f5 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -957,6 +957,7 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
 	/* Initialize f2fs-specific inode info */
 	atomic_set(&fi->dirty_pages, 0);
 	init_rwsem(&fi->i_sem);
+	spin_lock_init(&fi->i_size_lock);
 	INIT_LIST_HEAD(&fi->dirty_list);
 	INIT_LIST_HEAD(&fi->gdirty_list);
 	INIT_LIST_HEAD(&fi->inmem_ilist);
-- 
2.18.0.rc1




> 
> thank you and regards,
> 	o.
> 
>> thank you and regards,
>> 	o.
>>
>>> Thanks,
>>>
>>>>
>>>> So it's probably not inode locking.
>>>>
>>>>> root@tbs2[/proc/sys/kernel] # dmesg | grep down_read | wc -l
>>>>> 16
>>>>> root@tbs2[/proc/sys/kernel] # dmesg | grep up_read | wc -l
>>>>> 16
>>>>>
>>>>> regards,
>>>>> 	o.
>>>>>
>>>>>> thank you,
>>>>>> 	o.
>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>>> [  246.758190]  r5:eff213b0 r4:da283c60
>>>>>>>>> [  246.758198] [<c0435578>] (f2fs_write_single_data_page) from [<c0435fd8>] (f2fs_write_cache_pages+0x2b4/0x7c4)
>>>>>>>>> [  246.758204]  r10:da645c28 r9:da283d60 r8:da283c60 r7:0000000f r6:da645d80 r5:00000001
>>>>>>>>> [  246.758206]  r4:eff213b0
>>>>>>>>> [  246.758214] [<c0435d24>] (f2fs_write_cache_pages) from [<c043682c>] (f2fs_write_data_pages+0x344/0x35c)
>>>>>>>>> [  246.758220]  r10:00000000 r9:d9ed002c r8:d9ed0000 r7:00000004 r6:da283d60 r5:da283c60
>>>>>>>>> [  246.758223]  r4:da645d80
>>>>>>>>> [  246.758238] [<c04364e8>] (f2fs_write_data_pages) from [<c0267ee8>] (do_writepages+0x3c/0xd4)
>>>>>>>>> [  246.758244]  r10:0000000a r9:c0e03d00 r8:00000c00 r7:c0264ddc r6:da645d80 r5:da283d60
>>>>>>>>> [  246.758246]  r4:da283c60
>>>>>>>>> [  246.758254] [<c0267eac>] (do_writepages) from [<c0310cbc>] (__writeback_single_inode+0x44/0x454)
>>>>>>>>> [  246.758259]  r7:da283d60 r6:da645eac r5:da645d80 r4:da283c60
>>>>>>>>> [  246.758266] [<c0310c78>] (__writeback_single_inode) from [<c03112d0>] (writeback_sb_inodes+0x204/0x4b0)
>>>>>>>>> [  246.758272]  r10:0000000a r9:c0e03d00 r8:da283cc8 r7:da283c60 r6:da645eac r5:da283d08
>>>>>>>>> [  246.758274]  r4:d9dc9848
>>>>>>>>> [  246.758281] [<c03110cc>] (writeback_sb_inodes) from [<c03115cc>] (__writeback_inodes_wb+0x50/0xe4)
>>>>>>>>> [  246.758287]  r10:da3797a8 r9:c0e03d00 r8:d9dc985c r7:da645eac r6:00000000 r5:d9dc9848
>>>>>>>>> [  246.758289]  r4:da5a8800
>>>>>>>>> [  246.758296] [<c031157c>] (__writeback_inodes_wb) from [<c03118f4>] (wb_writeback+0x294/0x338)
>>>>>>>>> [  246.758302]  r10:fffbf200 r9:da644000 r8:c0e04e64 r7:d9dc9848 r6:d9dc9874 r5:da645eac
>>>>>>>>> [  246.758305]  r4:d9dc9848
>>>>>>>>> [  246.758312] [<c0311660>] (wb_writeback) from [<c0312dac>] (wb_workfn+0x35c/0x54c)
>>>>>>>>> [  246.758318]  r10:da5f2005 r9:d9dc984c r8:d9dc9948 r7:d9dc9848 r6:00000000 r5:d9dc9954
>>>>>>>>> [  246.758321]  r4:000031e6
>>>>>>>>> [  246.758334] [<c0312a50>] (wb_workfn) from [<c014f2b8>] (process_one_work+0x214/0x544)
>>>>>>>>> [  246.758340]  r10:da5f2005 r9:00000200 r8:00000000 r7:da5f2000 r6:ef044400 r5:da5eb000
>>>>>>>>> [  246.758343]  r4:d9dc9954
>>>>>>>>> [  246.758350] [<c014f0a4>] (process_one_work) from [<c014f634>] (worker_thread+0x4c/0x574)
>>>>>>>>> [  246.758357]  r10:ef044400 r9:c0e03d00 r8:ef044418 r7:00000088 r6:ef044400 r5:da5eb014
>>>>>>>>> [  246.758359]  r4:da5eb000
>>>>>>>>> [  246.758368] [<c014f5e8>] (worker_thread) from [<c01564fc>] (kthread+0x144/0x170)
>>>>>>>>> [  246.758374]  r10:ec9e5e90 r9:dabf325c r8:da5eb000 r7:da644000 r6:00000000 r5:da5fe000
>>>>>>>>> [  246.758377]  r4:dabf3240
>>>>>>>>> [  246.758386] [<c01563b8>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
>>>>>>>>> [  246.758391] Exception stack(0xda645fb0 to 0xda645ff8)
>>>>>>>>> [  246.758397] 5fa0:                                     00000000 00000000 00000000 00000000
>>>>>>>>> [  246.758402] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>>>>>>>> [  246.758407] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>>>>>>>> [  246.758413]  r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:c01563b8
>>>>>>>>> [  246.758416]  r4:da5fe000
>>>>>>>>> .
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> Linux-f2fs-devel mailing list
>>>>>>>> Linux-f2fs-devel@lists.sourceforge.net
>>>>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>>>>>
>>>> .
>>>>
> .
>