linux-kernel - [GIT PULL] fscache: Fix incorrect mixing of wake/wait and missing barriers

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Message-ID: <3425804.1675083883@warthog.procyon.org.uk>
Date:   Mon, 30 Jan 2023 13:04:43 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     David Howells <dhowells@...hat.com>,
        Hou Tao <houtao@...weicloud.com>,
        Jeff Layton <jlayton@...nel.org>,
        Jingbo Xu <jefflexu@...ux.alibaba.com>, houtao1@...wei.com,
        linux-cachefs@...hat.com, linux-erofs@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [GIT PULL] fscache: Fix incorrect mixing of wake/wait and missing barriers

Hi Linus,

Could you pull these fixes from Hou Tao please?  There are two problems
fixed in fscache volume handling:

 (1) wake_up_bit() is incorrectly paired with wait_var_event().  The latter
     selects the waitqueue to use differently.

 (2) Missing barriers ordering between state bit and task state.

Thanks,
David

To quote Hou Tao:

    The patchset includes two fixes for fscache volume operations: patch 1
    fixes the hang problem during volume acquisition when the volume
    acquisition process waits for the freeing of relinquished volume, patch
    2 adds the missing memory barrier in fscache_create_volume_work() and it
    is spotted through code review when checking whether or not these is
    missing smp_mb() before invoking wake_up_bit().

    Change Log:
    v3:
     * Use clear_and_wake_up_bit() helper (Suggested by Jingbo Xu)
     * Tidy up commit message and add Reviewed-by tag

    v2: https://listman.redhat.com/archives/linux-cachefs/2022-December/007402.html
     * rebased on v6.1-rc1
     * Patch 1: use wait_on_bit() instead (Suggested by David)
     * Patch 2: add the missing smp_mb() in fscache_create_volume_work()

    v1: https://listman.redhat.com/archives/linux-cachefs/2022-December/007384.html

Link: https://lore.kernel.org/r/20230113115211.2895845-1-houtao@huaweicloud.com
---
The following changes since commit 6d796c50f84ca79f1722bb131799e5a5710c4700:

  Linux 6.2-rc6 (2023-01-29 13:59:43 -0800)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/fscache-fixes-20230130

for you to fetch changes up to 3288666c72568fe1cc7f5c5ae33dfd3ab18004c8:

  fscache: Use clear_and_wake_up_bit() in fscache_create_volume_work() (2023-01-30 12:51:54 +0000)

----------------------------------------------------------------
fscache fixes

----------------------------------------------------------------
Hou Tao (2):
      fscache: Use wait_on_bit() to wait for the freeing of relinquished volume
      fscache: Use clear_and_wake_up_bit() in fscache_create_volume_work()

 fs/fscache/volume.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)