[PATCH v3.1 0/2] btrfs: trim enhancement to allow btrfs really trim block groups

[PATCH v3.1 0/2] btrfs: trim enhancement to allow btrfs really trim block groups

[Qu Wenruo]

This patchset can be fetched from github:
https://github.com/adam900710/linux/tree/trim_fix
Which is based on v4.19-rc1 tag.

This patchset introduces 2 enhancement, one to output better error
messages during trim, the other one is to ensure we could really trim
block groups if logical bytenr of block groups are beyond physical
device size.

These two patches are in the wild for a long time, and are pretty small
and the 2nd patch in facts fix a regression, and we already have test
case for it (btrfs/156).

Changelog:
v2:
  Only report total number of errors and first errno to make it less
  noisy.
  Change message level from warning to debug
v3:
  Rebase to v4.19-rc1.
  Change back message level from debug to warning since it's less noisy
  and will only report total failed bgs and devices.

v3.1
  Remove the "last error" output from first patch.

Qu Wenruo (2):
  btrfs: Enhance btrfs_trim_fs function to handle error better
  btrfs: Ensure btrfs_trim_fs can trim the whole fs

 fs/btrfs/extent-tree.c | 65 ++++++++++++++++++++++++++----------------
 fs/btrfs/ioctl.c       | 11 ++++---
 2 files changed, 47 insertions(+), 29 deletions(-)

-- 
2.18.0

[PATCH v3.1 1/2] btrfs: Enhance btrfs_trim_fs function to handle error better

[Qu Wenruo]

Function btrfs_trim_fs() doesn't handle errors in a consistent way, if
error happens when trimming existing block groups, it will skip the
remaining blocks and continue to trim unallocated space for each device.

And the return value will only reflect the final error from device
trimming.

This patch will fix such behavior by:

1) Recording last error from block group or device trimming
   So return value will also reflect the last error during trimming.
   Make developer more aware of the problem.

2) Continuing trimming if we can
   If we failed to trim one block group or device, we could still try
   next block group or device.

3) Report number of failures during block group and device trimming
   So it would be less noisy, but still gives user a brief summary of
   what's going wrong.

Such behavior can avoid confusion for case like failure to trim the
first block group and then only unallocated space is trimmed.

Reported-by: Chris Murphy <lists@colorremedies.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent-tree.c | 55 ++++++++++++++++++++++++++++++------------
 1 file changed, 39 insertions(+), 16 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index de6f75f5547b..2cc449190578 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10832,6 +10832,16 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
 	return ret;
 }
 
+/*
+ * Trim the whole fs, by:
+ * 1) Trimming free space in each block group
+ * 2) Trimming unallocated space in each device
+ *
+ * Will try to continue trimming even if we failed to trim one block group or
+ * device.
+ * The return value will be the last error during trim.
+ * Or 0 if nothing wrong happened.
+ */
 int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 {
 	struct btrfs_block_group_cache *cache = NULL;
@@ -10842,6 +10852,10 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 	u64 end;
 	u64 trimmed = 0;
 	u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
+	u64 bg_failed = 0;
+	u64 dev_failed = 0;
+	int bg_ret = 0;
+	int dev_ret = 0;
 	int ret = 0;
 
 	/*
@@ -10852,7 +10866,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 	else
 		cache = btrfs_lookup_block_group(fs_info, range->start);
 
-	while (cache) {
+	for (; cache; cache = next_block_group(fs_info, cache)) {
 		if (cache->key.objectid >= (range->start + range->len)) {
 			btrfs_put_block_group(cache);
 			break;
@@ -10866,45 +10880,54 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 			if (!block_group_cache_done(cache)) {
 				ret = cache_block_group(cache, 0);
 				if (ret) {
-					btrfs_put_block_group(cache);
-					break;
+					bg_failed++;
+					bg_ret = ret;
+					continue;
 				}
 				ret = wait_block_group_cache_done(cache);
 				if (ret) {
-					btrfs_put_block_group(cache);
-					break;
+					bg_failed++;
+					bg_ret = ret;
+					continue;
 				}
 			}
-			ret = btrfs_trim_block_group(cache,
-						     &group_trimmed,
-						     start,
-						     end,
-						     range->minlen);
+			ret = btrfs_trim_block_group(cache, &group_trimmed,
+						start, end, range->minlen);
 
 			trimmed += group_trimmed;
 			if (ret) {
-				btrfs_put_block_group(cache);
-				break;
+				bg_failed++;
+				bg_ret = ret;
+				continue;
 			}
 		}
-
-		cache = next_block_group(fs_info, cache);
 	}
 
+	if (bg_failed)
+		btrfs_warn(fs_info, "failed to trim %llu block group(s)",
+			   bg_failed);
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 	devices = &fs_info->fs_devices->alloc_list;
 	list_for_each_entry(device, devices, dev_alloc_list) {
 		ret = btrfs_trim_free_extents(device, range->minlen,
 					      &group_trimmed);
-		if (ret)
+		if (ret) {
+			dev_failed++;
+			dev_ret = ret;
 			break;
+		}
 
 		trimmed += group_trimmed;
 	}
 	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
+	if (dev_failed)
+		btrfs_warn(fs_info, "failed to trim %llu device(s)",
+			   dev_failed);
 	range->len = trimmed;
-	return ret;
+	if (bg_ret)
+		return bg_ret;
+	return dev_ret;
 }
 
 /*
-- 
2.18.0

[PATCH v3.1 2/2] btrfs: Ensure btrfs_trim_fs can trim the whole fs

[Qu Wenruo]

[BUG]
fstrim on some btrfs only trims the unallocated space, not trimming any
space in existing block groups.

[CAUSE]
Before fstrim_range passed to btrfs_trim_fs(), it get truncated to
range [0, super->total_bytes).
So later btrfs_trim_fs() will only be able to trim block groups in range
[0, super->total_bytes).

While for btrfs, any bytenr aligned to sector size is valid, since btrfs use
its logical address space, there is nothing limiting the location where
we put block groups.

For btrfs with routine balance, it's quite easy to relocate all
block groups and bytenr of block groups will start beyond super->total_bytes.

In that case, btrfs will not trim existing block groups.

[FIX]
Just remove the truncation in btrfs_ioctl_fitrim(), so btrfs_trim_fs()
can get the unmodified range, which is normally set to [0, U64_MAX].

Reported-by: Chris Murphy <lists@colorremedies.com>
Fixes: f4c697e6406d ("btrfs: return EINVAL if start > total_bytes in fitrim ioctl")
Cc: <stable@vger.kernel.org> # v4.0+
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent-tree.c | 10 +---------
 fs/btrfs/ioctl.c       | 11 +++++++----
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 2cc449190578..c6a9cca8ddca 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10851,21 +10851,13 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 	u64 start;
 	u64 end;
 	u64 trimmed = 0;
-	u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
 	u64 bg_failed = 0;
 	u64 dev_failed = 0;
 	int bg_ret = 0;
 	int dev_ret = 0;
 	int ret = 0;
 
-	/*
-	 * try to trim all FS space, our block group may start from non-zero.
-	 */
-	if (range->len == total_bytes)
-		cache = btrfs_lookup_first_block_group(fs_info, range->start);
-	else
-		cache = btrfs_lookup_block_group(fs_info, range->start);
-
+	cache = btrfs_lookup_first_block_group(fs_info, range->start);
 	for (; cache; cache = next_block_group(fs_info, cache)) {
 		if (cache->key.objectid >= (range->start + range->len)) {
 			btrfs_put_block_group(cache);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 63600dc2ac4c..8165a4bfa579 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -491,7 +491,6 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
 	struct fstrim_range range;
 	u64 minlen = ULLONG_MAX;
 	u64 num_devices = 0;
-	u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
 	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -515,11 +514,15 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
 		return -EOPNOTSUPP;
 	if (copy_from_user(&range, arg, sizeof(range)))
 		return -EFAULT;
-	if (range.start > total_bytes ||
-	    range.len < fs_info->sb->s_blocksize)
+
+	/*
+	 * NOTE: Don't truncate the range using super->total_bytes.
+	 * Bytenr of btrfs block group is in btrfs logical address space,
+	 * which can be any sector size aligned bytenr in [0, U64_MAX].
+	 */
+	if (range.len < fs_info->sb->s_blocksize)
 		return -EINVAL;
 
-	range.len = min(range.len, total_bytes - range.start);
 	range.minlen = max(range.minlen, minlen);
 	ret = btrfs_trim_fs(fs_info, &range);
 	if (ret < 0)
-- 
2.18.0

Re: [PATCH v3.1 1/2] btrfs: Enhance btrfs_trim_fs function to handle error better

[David Sterba]

On Fri, Sep 07, 2018 at 02:16:23PM +0800, Qu Wenruo wrote:
> Function btrfs_trim_fs() doesn't handle errors in a consistent way, if
> error happens when trimming existing block groups, it will skip the
> remaining blocks and continue to trim unallocated space for each device.
> 
> And the return value will only reflect the final error from device
> trimming.
> 
> This patch will fix such behavior by:
> 
> 1) Recording last error from block group or device trimming
>    So return value will also reflect the last error during trimming.
>    Make developer more aware of the problem.
> 
> 2) Continuing trimming if we can
>    If we failed to trim one block group or device, we could still try
>    next block group or device.
> 
> 3) Report number of failures during block group and device trimming
>    So it would be less noisy, but still gives user a brief summary of
>    what's going wrong.
> 
> Such behavior can avoid confusion for case like failure to trim the
> first block group and then only unallocated space is trimmed.
> 
> Reported-by: Chris Murphy <lists@colorremedies.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: David Sterba <dsterba@suse.com>

> -			ret = btrfs_trim_block_group(cache,
> -						     &group_trimmed,
> -						     start,
> -						     end,
> -						     range->minlen);
> +			ret = btrfs_trim_block_group(cache, &group_trimmed,
> +						start, end, range->minlen);

No unrealted changes please, this just reformats the argument list.

Re: [PATCH v3.1 1/2] btrfs: Enhance btrfs_trim_fs function to handle error better

[David Sterba]

On Fri, Sep 07, 2018 at 02:16:23PM +0800, Qu Wenruo wrote:
> +	if (bg_failed)
> +		btrfs_warn(fs_info, "failed to trim %llu block group(s)",
> +			   bg_failed);

> +	if (dev_failed)
> +		btrfs_warn(fs_info, "failed to trim %llu device(s)",
> +			   dev_failed);

Minor update, I've added bg_ret and dev_ret to the messages as this will
end up in the logs and could be useful for later analysis.

Re: [PATCH v3.1 2/2] btrfs: Ensure btrfs_trim_fs can trim the whole fs

[David Sterba]

On Fri, Sep 07, 2018 at 02:16:24PM +0800, Qu Wenruo wrote:
> [BUG]
> fstrim on some btrfs only trims the unallocated space, not trimming any
> space in existing block groups.
> 
> [CAUSE]
> Before fstrim_range passed to btrfs_trim_fs(), it get truncated to
> range [0, super->total_bytes).
> So later btrfs_trim_fs() will only be able to trim block groups in range
> [0, super->total_bytes).
> 
> While for btrfs, any bytenr aligned to sector size is valid, since btrfs use
> its logical address space, there is nothing limiting the location where
> we put block groups.
> 
> For btrfs with routine balance, it's quite easy to relocate all
> block groups and bytenr of block groups will start beyond super->total_bytes.
> 
> In that case, btrfs will not trim existing block groups.
> 
> [FIX]
> Just remove the truncation in btrfs_ioctl_fitrim(), so btrfs_trim_fs()
> can get the unmodified range, which is normally set to [0, U64_MAX].
> 
> Reported-by: Chris Murphy <lists@colorremedies.com>
> Fixes: f4c697e6406d ("btrfs: return EINVAL if start > total_bytes in fitrim ioctl")
> Cc: <stable@vger.kernel.org> # v4.0+
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: David Sterba <dsterba@suse.com>