On Thu, Oct 12, 2023 at 02:27:40PM +0200, Zbigniew Lukwinski wrote:
From: Jan Kara jack@suse.cz
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-AM... Reported-by: Eric Whitney enwlinux@gmail.com Fixes: dabc8b207566 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide") CC: stable@vger.kernel.org Signed-off-by: Jan Kara jack@suse.cz
fs/quota/dquot.c | 66 ++++++++++++++++++++++++---------------- include/linux/quota.h | 4 ++- include/linux/quotaops.h | 2 +- 3 files changed, 43 insertions(+), 29 deletions(-)
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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.
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