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Date: Thu, 28 May 2020 22:44:01 -0400 From: "Theodore Y. Ts'o" <tytso@....edu> To: Jan Kara <jack@...e.cz> Cc: linux-ext4@...r.kernel.org, stable@...r.kernel.org Subject: Re: [PATCH 2/2] jbd2: Avoid leaking transaction credits when unreserving handle On Wed, May 20, 2020 at 03:31:19PM +0200, Jan Kara wrote: > When reserved transaction handle is unused, we subtract its reserved > credits in __jbd2_journal_unreserve_handle() called from > jbd2_journal_stop(). However this function forgets to remove reserved > credits from transaction->t_outstanding_credits and thus the transaction > space that was reserved remains effectively leaked. The leaked > transaction space can be quite significant in some cases and leads to > unnecessarily small transactions and thus reducing throughput of the > journalling machinery. E.g. fsmark workload creating lots of 4k files > was observed to have about 20% lower throughput due to this when ext4 is > mounted with dioread_nolock mount option. > > Subtract reserved credits from t_outstanding_credits as well. > > CC: stable@...r.kernel.org > Fixes: 8f7d89f36829 ("jbd2: transaction reservation support") > Reviewed-by: Andreas Dilger <adilger@...ger.ca> > Signed-off-by: Jan Kara <jack@...e.cz> Thanks, applied. - Ted
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