linux-ext4 - [PATCH v2 12/22] jbd2: don't read journal->j_commit

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Date:   Thu,  5 Nov 2020 19:59:01 -0800
From:   Harshad Shirwadkar <harshadshirwadkar@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     tytso@....edu, Harshad Shirwadkar <harshadshirwadkar@...il.com>
Subject: [PATCH v2 12/22] jbd2: don't read journal->j_commit_sequence without taking a lock

Take journal state lock before reading journal->j_commit_sequence.

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
---
 fs/jbd2/journal.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b5fbcd1b444c..f7ebf6ef69af 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -734,10 +734,12 @@ int jbd2_fc_begin_commit(journal_t *journal, tid_t tid)
 	if (!journal->j_stats.ts_tid)
 		return -EINVAL;
 
-	if (tid <= journal->j_commit_sequence)
+	write_lock(&journal->j_state_lock);
+	if (tid <= journal->j_commit_sequence) {
+		write_unlock(&journal->j_state_lock);
 		return -EALREADY;
+	}
 
-	write_lock(&journal->j_state_lock);
 	if (journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
 	    (journal->j_flags & JBD2_FAST_COMMIT_ONGOING)) {
 		DEFINE_WAIT(wait);
-- 
2.29.1.341.ge80a0c044ae-goog