[1/2] btrfs: punt all bios created in btrfs_submit_compressed_write()
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Message ID d934383ea528d920a95b6107daad6023b516f0f4.1576109087.git.dennis@kernel.org
State New
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Series
  • [1/2] btrfs: punt all bios created in btrfs_submit_compressed_write()
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Commit Message

Dennis Zhou Dec. 12, 2019, 12:07 a.m. UTC
Compressed writes happen in the background via kworkers. However, this
causes bios to be attributed to root bypassing any cgroup limits from
the actual writer. We tag the first bio with REQ_CGROUP_PUNT, which will
punt the bio to an appropriate cgroup specific workqueue and attribute
the IO properly. However, if btrfs_submit_compressed_write() creates a
new bio, we don't tag it the same way. Add the appropriate tagging for
subsequent bios.

Fixes: ec39f7696ccfa ("Btrfs: use REQ_CGROUP_PUNT for worker thread submitted bios")
Cc: Chris Mason <clm@fb.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/compression.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Chris Mason Dec. 12, 2019, 12:15 a.m. UTC | #1
On 11 Dec 2019, at 19:07, Dennis Zhou wrote:

> Compressed writes happen in the background via kworkers. However, this
> causes bios to be attributed to root bypassing any cgroup limits from
> the actual writer. We tag the first bio with REQ_CGROUP_PUNT, which 
> will
> punt the bio to an appropriate cgroup specific workqueue and attribute
> the IO properly. However, if btrfs_submit_compressed_write() creates a
> new bio, we don't tag it the same way. Add the appropriate tagging for
> subsequent bios.
>
> Fixes: ec39f7696ccfa ("Btrfs: use REQ_CGROUP_PUNT for worker thread 
> submitted bios")
> Cc: Chris Mason <clm@fb.com>
> Signed-off-by: Dennis Zhou <dennis@kernel.org>

Good catch Dennis.  The compression code should end up limiting the size 
of the bio such that we'll never actually fail to bio_add_page(), but 
this is still the right thing to do.

Reviewed-by: Chris Mason <clm@fb.com>

-chris
David Sterba Dec. 30, 2019, 3:08 p.m. UTC | #2
On Wed, Dec 11, 2019 at 04:07:06PM -0800, Dennis Zhou wrote:
> Compressed writes happen in the background via kworkers. However, this
> causes bios to be attributed to root bypassing any cgroup limits from
> the actual writer. We tag the first bio with REQ_CGROUP_PUNT, which will
> punt the bio to an appropriate cgroup specific workqueue and attribute
> the IO properly. However, if btrfs_submit_compressed_write() creates a
> new bio, we don't tag it the same way. Add the appropriate tagging for
> subsequent bios.
> 
> Fixes: ec39f7696ccfa ("Btrfs: use REQ_CGROUP_PUNT for worker thread submitted bios")
> Cc: Chris Mason <clm@fb.com>
> Signed-off-by: Dennis Zhou <dennis@kernel.org>

1 and 2 queued for 5.5-rc, thanks.

Patch
diff mbox series

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index ed05e5277399..4ce81571f0cd 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -491,6 +491,10 @@  blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
 			bio->bi_opf = REQ_OP_WRITE | write_flags;
 			bio->bi_private = cb;
 			bio->bi_end_io = end_compressed_bio_write;
+			if (blkcg_css) {
+				bio->bi_opf |= REQ_CGROUP_PUNT;
+				bio_associate_blkg_from_css(bio, blkcg_css);
+			}
 			bio_add_page(bio, page, PAGE_SIZE, 0);
 		}
 		if (bytes_left < PAGE_SIZE) {