Attachment 837903 Details for Bug 1169774

[patch] [PATCH] jbd2: Avoid leaking transaction credits when unreserving

0001-jbd2-Avoid-leaking-transaction-credits-when-unreserv.patch (text/plain), 2.64 KB, created by Jan Kara on 2020-05-18 08:12:09 UTC

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Creator: Jan Kara

Created: 2020-05-18 08:12:09 UTC

Size: 2.64 KB

patch

obsolete

>From 90479bd92c85c24d992f9b2c5791cc9d913c0c6d Mon Sep 17 00:00:00 2001
>From: Jan Kara <jack@suse.cz>
>Date: Sat, 16 May 2020 00:18:18 +0200
>Subject: [PATCH] jbd2: Avoid leaking transaction credits when unreserving
> handle
>
>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@vger.kernel.org
>Fixes: 8f7d89f36829 ("jbd2: transaction reservation support")
>Signed-off-by: Jan Kara <jack@suse.cz>
>---
> fs/jbd2/transaction.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
>diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
>index 3dccc23cf010..b49a103cff1f 100644
>--- a/fs/jbd2/transaction.c
>+++ b/fs/jbd2/transaction.c
>@@ -541,17 +541,24 @@ handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
> }
> EXPORT_SYMBOL(jbd2_journal_start);
> 
>-static void __jbd2_journal_unreserve_handle(handle_t *handle)
>+static void __jbd2_journal_unreserve_handle(handle_t *handle, transaction_t *t)
> {
> 	journal_t *journal = handle->h_journal;
> 
> 	WARN_ON(!handle->h_reserved);
> 	sub_reserved_credits(journal, handle->h_total_credits);
>+	if (t)
>+		atomic_sub(handle->h_total_credits, &t->t_outstanding_credits);
> }
> 
> void jbd2_journal_free_reserved(handle_t *handle)
> {
>-	__jbd2_journal_unreserve_handle(handle);
>+	journal_t *journal = handle->h_journal;
>+
>+	/* Get j_state_lock to pin running transaction if it exists */
>+	read_lock(&journal->j_state_lock);
>+	__jbd2_journal_unreserve_handle(handle, journal->j_running_transaction);
>+	read_unlock(&journal->j_state_lock);
> 	jbd2_free_handle(handle);
> }
> EXPORT_SYMBOL(jbd2_journal_free_reserved);
>@@ -721,8 +728,10 @@ static void stop_this_handle(handle_t *handle)
> 	}
> 	atomic_sub(handle->h_total_credits,
> 		   &transaction->t_outstanding_credits);
>-	if (handle->h_rsv_handle)
>-		__jbd2_journal_unreserve_handle(handle->h_rsv_handle);
>+	if (handle->h_rsv_handle) {
>+		__jbd2_journal_unreserve_handle(handle->h_rsv_handle,
>+						transaction);
>+	}
> 	if (atomic_dec_and_test(&transaction->t_updates))
> 		wake_up(&journal->j_wait_updates);
> 
>-- 
>2.16.4
>

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Attachments on bug 1169774: 836248 | 836252 | 836392 | 836393 | 837072 | 837073 | 837180 | 837903 | 843540