Re: [PATCH 6.6.y 2/2] jbd2: bound shrinker scans by examined checkpoint buffers

[sashiko-bot@kernel.org]

> From: Max Kellermann <max.kellermann@ionos.com>
> 
> [ Upstream commit 15cb16496446b94e67f7abcb049b8e2c75cd3d02 ]
> 
> The jbd2 shrinker currently accounts only checkpoint buffers that it
> successfully releases against nr_to_scan.  Busy buffers therefore do not
> consume the scan budget.
> 
> If a checkpoint transaction contains mostly busy buffers, the shrinker
> can scan its entire checkpoint list while holding journal->j_list_lock.
> Large checkpoint lists can result in excessive lock hold times and leave
> other CPUs spinning on j_list_lock, causing soft lockups or RCU stalls.
> 
> Pass nr_to_scan into journal_shrink_one_cp_list() and decrement it for
> every buffer examined, including busy buffers.  Pass NULL from checkpoint
> [ ... ]
> Reviewed-by: Jan Kara <jack@suse.cz>
> Link: https://patch.msgid.link/20260713102229.1598812-3-max.kellermann@ionos.com
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Assisted-by: LLM
> Signed-off-by: Artem Dinaburg <artem@trailofbits.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261008192048.98833-1-artem@trailofbits.com?part=2