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jbd2: check need_resched() when skipping busy checkpoint buffers

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journal_shrink_one_cp_list() skips busy checkpoint buffers when called
with JBD2_SHRINK_BUSY_SKIP.  The continue statement on this path also
skips the need_resched() check at the end of the loop body.

Consequently, when a checkpoint list contains mostly busy buffers, the
shrinker can walk the entire list while holding journal->j_list_lock,
even when a reschedule has been requested.  Large checkpoint lists under
memory pressure can therefore cause long lock hold times and leave other
CPUs spinning on j_list_lock, resulting in soft lockups or RCU stalls.

Route the busy-buffer path through the need_resched() check so that the
shrinker can release j_list_lock and reschedule promptly, restoring
parity with the clean-buffer path, which already checks need_resched().
This does not change which checkpoint buffers are eligible for removal.

Fixes: b98dba273a ("jbd2: remove journal_clean_one_cp_list()")
Cc: stable@vger.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260713102229.1598812-2-max.kellermann@ionos.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Max Kellermann 2026-07-13 12:22:28 +02:00 committed by Theodore Ts'o
parent fef5265969
commit f213e12ff5
1 changed files with 2 additions and 1 deletions
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3
fs/jbd2/checkpoint.c
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@ -389,7 +389,7 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
ret = jbd2_journal_try_remove_checkpoint(jh);
if (ret < 0) {
if (type == JBD2_SHRINK_BUSY_SKIP)
continue;
goto next;
break;
}
}
@ -400,6 +400,7 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
break;
}
next:
if (need_resched())
break;
} while (jh != last_jh);