The state lock is taken after we are doing an assert on the state value, not before. It is also taken after the jbd_debug() call. Noting that jbd_debug() is implemented with two separate printk() calls, it can lead to corrupted and misleading debug output like the following (see lines marked with "*"): [ 290.339362] (fs/jbd2/journal.c, 203): kjournald2: kjournald2 wakes [ 290.339365] (fs/jbd2/journal.c, 155): kjournald2: commit_sequence=42103, commit_request=42104 [ 290.339369] (fs/jbd2/journal.c, 158): kjournald2: OK, requests differ [* 290.339376] (fs/jbd2/journal.c, 648): jbd2_log_wait_commit: [* 290.339379] (fs/jbd2/commit.c, 370): jbd2_journal_commit_transaction: JBD2: want 42104, j_commit_sequence=42103 [* 290.339382] JBD2: starting commit of transaction 42104 [ 290.339410] (fs/jbd2/revoke.c, 566): jbd2_journal_write_revoke_records: Wrote 0 revoke records [ 290.376555] (fs/jbd2/commit.c, 1088): jbd2_journal_commit_transaction: JBD2: commit 42104 complete, head 42079 i.e. the debug output from log_wait_commit and journal_commit_transaction have become interleaved. The output should have been: (fs/jbd2/journal.c, 648): jbd2_log_wait_commit: JBD2: want 42104, j_commit_sequence=42103 (fs/jbd2/commit.c, 370): jbd2_journal_commit_transaction: JBD2: starting commit of transaction 42104 It is expected that this is not easy to replicate -- I was only able to cause it on preempt-rt kernels, and even then only under heavy I/O load. Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> --- fs/jbd2/commit.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index 0f53946..7e8a5fd 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -423,6 +423,8 @@ void jbd2_journal_commit_transaction(journal_t *journal) J_ASSERT(journal->j_running_transaction != NULL); J_ASSERT(journal->j_committing_transaction == NULL); + write_lock(&journal->j_state_lock); + commit_transaction = journal->j_running_transaction; J_ASSERT(commit_transaction->t_state == T_RUNNING); @@ -430,7 +432,6 @@ void jbd2_journal_commit_transaction(journal_t *journal) jbd_debug(1, "JBD2: starting commit of transaction %d\n", commit_transaction->t_tid); - write_lock(&journal->j_state_lock); commit_transaction->t_state = T_LOCKED; trace_jbd2_commit_locking(journal, commit_transaction); -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
