linux-stable.git/block/bio.c, branch v5.17.2

block: fix rq-qos breakage from skipping rq_qos_done_bio()

2022-04-08T11:57:26+00:00

commit aa1b46dcdc7baaf5fec0be25782ef24b26aa209e upstream.

a647a524a467 ("block: don't call rq_qos_ops->done_bio if the bio isn't
tracked") made bio_endio() skip rq_qos_done_bio() if BIO_TRACKED is not set.
While this fixed a potential oops, it also broke blk-iocost by skipping the
done_bio callback for merged bios.

Before, whether a bio goes through rq_qos_throttle() or rq_qos_merge(),
rq_qos_done_bio() would be called on the bio on completion with BIO_TRACKED
distinguishing the former from the latter. rq_qos_done_bio() is not called
for bios which wenth through rq_qos_merge(). This royally confuses
blk-iocost as the merged bios never finish and are considered perpetually
in-flight.

One reliably reproducible failure mode is an intermediate cgroup geting
stuck active preventing its children from being activated due to the
leaf-only rule, leading to loss of control. The following is from
resctl-bench protection scenario which emulates isolating a web server like
workload from a memory bomb run on an iocost configuration which should
yield a reasonable level of protection.

  # cat /sys/block/nvme2n1/device/model
  Samsung SSD 970 PRO 512GB
  # cat /sys/fs/cgroup/io.cost.model
  259:0 ctrl=user model=linear rbps=834913556 rseqiops=93622 rrandiops=102913 wbps=618985353 wseqiops=72325 wrandiops=71025
  # cat /sys/fs/cgroup/io.cost.qos
  259:0 enable=1 ctrl=user rpct=95.00 rlat=18776 wpct=95.00 wlat=8897 min=60.00 max=100.00
  # resctl-bench -m 29.6G -r out.json run protection::scenario=mem-hog,loops=1
  ...
  Memory Hog Summary
  ==================

  IO Latency: R p50=242u:336u/2.5m p90=794u:1.4m/7.5m p99=2.7m:8.0m/62.5m max=8.0m:36.4m/350m
              W p50=221u:323u/1.5m p90=709u:1.2m/5.5m p99=1.5m:2.5m/9.5m max=6.9m:35.9m/350m

  Isolation and Request Latency Impact Distributions:

                min   p01   p05   p10   p25   p50   p75   p90   p95   p99   max  mean stdev
  isol%       15.90 15.90 15.90 40.05 57.24 59.07 60.01 74.63 74.63 90.35 90.35 58.12 15.82
  lat-imp%        0     0     0     0     0  4.55 14.68 15.54 233.5 548.1 548.1 53.88 143.6

  Result: isol=58.12:15.82% lat_imp=53.88%:143.6 work_csv=100.0% missing=3.96%

The isolation result of 58.12% is close to what this device would show
without any IO control.

Fix it by introducing a new flag BIO_QOS_MERGED to mark merged bios and
calling rq_qos_done_bio() on them too. For consistency and clarity, rename
BIO_TRACKED to BIO_QOS_THROTTLED. The flag checks are moved into
rq_qos_done_bio() so that it's next to the code paths that set the flags.

With the patch applied, the above same benchmark shows:

  # resctl-bench -m 29.6G -r out.json run protection::scenario=mem-hog,loops=1
  ...
  Memory Hog Summary
  ==================

  IO Latency: R p50=123u:84.4u/985u p90=322u:256u/2.5m p99=1.6m:1.4m/9.5m max=11.1m:36.0m/350m
              W p50=429u:274u/995u p90=1.7m:1.3m/4.5m p99=3.4m:2.7m/11.5m max=7.9m:5.9m/26.5m

  Isolation and Request Latency Impact Distributions:

                min   p01   p05   p10   p25   p50   p75   p90   p95   p99   max  mean stdev
  isol%       84.91 84.91 89.51 90.73 92.31 94.49 96.36 98.04 98.71 100.0 100.0 94.42  2.81
  lat-imp%        0     0     0     0     0  2.81  5.73 11.11 13.92 17.53 22.61  4.10  4.68

  Result: isol=94.42:2.81% lat_imp=4.10%:4.68 work_csv=58.34% missing=0%

Signed-off-by: Tejun Heo 
Fixes: a647a524a467 ("block: don't call rq_qos_ops->done_bio if the bio isn't tracked")
Cc: stable@vger.kernel.org # v5.15+
Cc: Ming Lei 
Cc: Yu Kuai 
Reviewed-by: Ming Lei 
Link: https://lore.kernel.org/r/Yi7rdrzQEHjJLGKB@slm.duckdns.org
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

block: Fix wrong offset in bio_truncate()

2022-01-20T13:30:12+00:00

bio_truncate() clears the buffer outside of last block of bdev, however
current bio_truncate() is using the wrong offset of page. So it can
return the uninitialized data.

This happened when both of truncated/corrupted FS and userspace (via
bdev) are trying to read the last of bdev.

Reported-by: syzbot+ac94ae5f68b84197f41c@syzkaller.appspotmail.com
Signed-off-by: OGAWA Hirofumi 
Reviewed-by: Ming Lei 
Link: https://lore.kernel.org/r/875yqt1c9g.fsf@mail.parknet.co.jp
Signed-off-by: Jens Axboe

Merge tag 'iomap-5.17' of git://git.infradead.org/users/willy/linux

2022-01-12T20:51:41+00:00

Pull iomap updates from Matthew Wilcox:
 "Convert xfs/iomap to use folios.

  This should be all that is needed for XFS to use large folios. There
  is no code in this pull request to create large folios, but no
  additional changes should be needed to XFS or iomap once they are
  created.

  Usually this would have come from Darrick, and we had intended that it
  would come that route. Between the holidays and various things which
  Darrick needed to work on, he asked if I could send things directly.

  There weren't any other iomap patches pending for this release, which
  probably also played a role"

* tag 'iomap-5.17' of git://git.infradead.org/users/willy/linux: (26 commits)
  iomap: Inline __iomap_zero_iter into its caller
  xfs: Support large folios
  iomap: Support large folios in invalidatepage
  iomap: Convert iomap_migrate_page() to use folios
  iomap: Convert iomap_add_to_ioend() to take a folio
  iomap: Simplify iomap_do_writepage()
  iomap: Simplify iomap_writepage_map()
  iomap,xfs: Convert ->discard_page to ->discard_folio
  iomap: Convert iomap_write_end_inline to take a folio
  iomap: Convert iomap_write_begin() and iomap_write_end() to folios
  iomap: Convert __iomap_zero_iter to use a folio
  iomap: Allow iomap_write_begin() to be called with the full length
  iomap: Convert iomap_page_mkwrite to use a folio
  iomap: Convert readahead and readpage to use a folio
  iomap: Convert iomap_read_inline_data to take a folio
  iomap: Use folio offsets instead of page offsets
  iomap: Convert bio completions to use folios
  iomap: Pass the iomap_page into iomap_set_range_uptodate
  iomap: Add iomap_invalidate_folio
  iomap: Convert iomap_releasepage to use a folio
  ...

block: Add bio_add_folio()

2021-12-16T20:49:51+00:00

This is a thin wrapper around bio_add_page().  The main advantage here
is the documentation that folios larger than 2GiB are not supported.
It's not currently possible to allocate folios that large, but if it
ever becomes possible, this function will fail gracefully instead of
doing I/O to the wrong bytes.

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Jens Axboe 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Darrick J. Wong

block: use singly linked list for bio cache

2021-12-16T15:43:09+00:00

Pointless to maintain a head/tail for the list, as we never need to
access the tail. Entries are always LIFO for cache hotness reasons.

Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

block: avoid extra iter advance with async iocb

2021-10-27T12:54:58+00:00

Nobody cares about iov iterators state if we return -EIOCBQUEUED, so as
the we now have __blkdev_direct_IO_async(), which gets pages only once,
we can skip expensive iov_iter_advance(). It's around 1-2% of all CPU
spent.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/a6158edfbfa2ae3bc24aed29a72f035df18fad2f.1635337135.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

block: refactor bio_iov_bvec_set()

2021-10-25T14:00:48+00:00

Combine bio_iov_bvec_set() and bio_iov_bvec_set_append() and let the
caller to do iov_iter_advance(). Also get rid of __bio_iov_bvec_set(),
which was duplicated in the final binary, and replace a weird
iov_iter_truncate() of a temporal iter copy with min() better reflecting
the intention.

Signed-off-by: Pavel Begunkov 
Reviewed-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/bcf1ac36fce769a514e19475f3623cd86a1d8b72.1635006010.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

block: inline a part of bio_release_pages()

2021-10-20T14:08:07+00:00

Inline BIO_NO_PAGE_REF check of bio_release_pages() to avoid function
call.

Signed-off-by: Pavel Begunkov 
Signed-off-by: Jens Axboe

block: don't bother iter advancing a fully done bio

2021-10-18T14:50:16+00:00

If we're completing nbytes and nbytes is the size of the bio, don't bother
with calling into the iterator increment helpers. Just clear the bio
size and we're done.

Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

block: use bdev_get_queue() in bio.c

2021-10-18T12:17:36+00:00

Convert bdev->bd_disk->queue to bdev_get_queue(), it's uses a cached
queue pointer and so is faster.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/85c36ea784d285a5075baa10049e6b59e15fb484.1634219547.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe