On Thu, Oct 12, 2023 at 02:27:40PM +0200, Zbigniew Lukwinski wrote:
> From: Jan Kara <jack@xxxxxxx>
>
> Eric has reported that commit dabc8b207566 ("quota: fix dqput() to
> follow the guarantees dquot_srcu should provide") heavily increases
> runtime of generic/270 xfstest for ext4 in nojournal mode. The reason
> for this is that ext4 in nojournal mode leaves dquots dirty until the last
> dqput() and thus the cleanup done in quota_release_workfn() has to write
> them all. Due to the way quota_release_workfn() is written this results
> in synchronize_srcu() call for each dirty dquot which makes the dquot
> cleanup when turning quotas off extremely slow.
>
> To be able to avoid synchronize_srcu() for each dirty dquot we need to
> rework how we track dquots to be cleaned up. Instead of keeping the last
> dquot reference while it is on releasing_dquots list, we drop it right
> away and mark the dquot with new DQ_RELEASING_B bit instead. This way we
> can we can remove dquot from releasing_dquots list when new reference to
> it is acquired and thus there's no need to call synchronize_srcu() each
> time we drop dq_list_lock.
>
> References: https://lore.kernel.org/all/ZRytn6CxFK2oECUt@debian-BULLSEYE-live-builder-AMD64
> Reported-by: Eric Whitney <enwlinux@xxxxxxxxx>
> Fixes: dabc8b207566 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide")
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/quota/dquot.c | 66 ++++++++++++++++++++++++----------------
> include/linux/quota.h | 4 ++-
> include/linux/quotaops.h | 2 +-
> 3 files changed, 43 insertions(+), 29 deletions(-)
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
