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authorJan Kara <jack@suse.cz>2020-05-20 15:31:19 +0200
committerTheodore Ts'o <tytso@mit.edu>2020-06-03 23:16:53 -0400
commit14ff6286309e2853aed50083c9a83328423fdd8c (patch)
tree03e7f6de9cd898f9506df9e67fabc96ed868e2ee /fs/jbd2
parentdfcd4489e270282d984cd06c00f3a45d52a3f0a7 (diff)
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") Reviewed-by: Andreas Dilger <adilger@dilger.ca> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20200520133119.1383-3-jack@suse.cz Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/jbd2')
-rw-r--r--fs/jbd2/transaction.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 3dccc23cf010..e91aad3637a2 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);
@@ -722,7 +729,8 @@ 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);
+ __jbd2_journal_unreserve_handle(handle->h_rsv_handle,
+ transaction);
if (atomic_dec_and_test(&transaction->t_updates))
wake_up(&journal->j_wait_updates);