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@gmail.com>
Link: https://lore.kernel.org/r/20201106035911.1942128-13-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b5fbcd1..f7ebf6e 100644 (file)
--- 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);