Re: [Devel] [PATCH hci-8.1 v7 0/8] block/blk-cbt: don't lose writes held across a dm suspend

[Konstantin Khorenko <khorenko@virtuozzo.com>]

On Wed, 28 Oct 2026 11:11:21 +0100, Pavel Tikhomirov wrote:
> block/blk-cbt: don't lose writes held across a dm suspend
> 
> Fix CBT missing writes that request-based dm holds across a suspend,
> which made incremental backups taken with ploop-backup silently lose
> data.
> 
> Claude tested full and incremental ploop-backup under write load (a
> random writer, and fio with 4 jobs x iodepth 64): the incremental backup
> lost blocks without the fix, and was consistent in 30/30 and 10/10 runs
> with it. CBT start/stop and device resize under fio ran without
> warnings. With writes throttled by io.max on a loop device, CBT recorded
> 24 of 64 written blocks without the throttle patch, and all 64 with it.
> A RWF_NOWAIT write into a missing bitmap page now fails with EAGAIN
> instead of sleeping, and succeeds when retried without RWF_NOWAIT.
> 
> [...]

Applied to branch-rh10-6.12.0-211.52.1.22.x.vz10-ovz, will be released in rh10-6.12.0-211.52.1.22.20.vz10, thanks!

[1/8] block/blk-cbt: don't read a released cbt in blk_cbt_update_size()
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/fbe0b01e6b34
[2/8] block/blk-cbt: shift the block size as unsigned
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/98a7e9b14dae
[3/8] block/blk-throttle: account a throttled write in CBT
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/3cc26f60a3e1
[4/8] block/blk-cbt: read a map slot once, publish a map page with release
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/0496ffc0eb88
[5/8] block/blk-cbt: don't overwrite a map page with CBT_PAGE_MISSED
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/f3cff5245f54
[6/8] block/blk-cbt: walk cbt_list under SRCU
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/67feb90954cb
[7/8] block/blk-cbt: don't sleep in CBT for a REQ_NOWAIT write
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/e30d37613466
[8/8] block/blk-cbt: account a write request also when dm starts it
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/fc8110343e64

-- 
Konstantin Khorenko,
Virtuozzo Linux Kernel Team


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