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| author | Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> | 2019-01-31 23:42:11 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2019-01-31 23:42:11 -0500 |
| commit | 53cf978457325d8fb2cdecd7981b31a8229e446e (patch) | |
| tree | f090389c633b762bdcfe55aafa796fc46dc06cbb /fs/jbd2/checkpoint.c | |
| parent | 8fdd60f2ae3682caf2a7258626abc21eb4711892 (diff) | |
| download | linux-53cf978457325d8fb2cdecd7981b31a8229e446e.tar.bz2 | |
jbd2: fix deadlock while checkpoint thread waits commit thread to finish
This issue was found when I tried to put checkpoint work in a separate thread,
the deadlock below happened:
Thread1 | Thread2
__jbd2_log_wait_for_space |
jbd2_log_do_checkpoint (hold j_checkpoint_mutex)|
if (jh->b_transaction != NULL) |
... |
jbd2_log_start_commit(journal, tid); |jbd2_update_log_tail
| will lock j_checkpoint_mutex,
| but will be blocked here.
|
jbd2_log_wait_commit(journal, tid); |
wait_event(journal->j_wait_done_commit, |
!tid_gt(tid, journal->j_commit_sequence)); |
... |wake_up(j_wait_done_commit)
} |
then deadlock occurs, Thread1 will never be waken up.
To fix this issue, drop j_checkpoint_mutex in jbd2_log_do_checkpoint()
when we are going to wait for transaction commit.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/jbd2/checkpoint.c')
| -rw-r--r-- | fs/jbd2/checkpoint.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c index 26f8d7e46462..02e0b79753e7 100644 --- a/fs/jbd2/checkpoint.c +++ b/fs/jbd2/checkpoint.c @@ -113,7 +113,7 @@ void __jbd2_log_wait_for_space(journal_t *journal) nblocks = jbd2_space_needed(journal); while (jbd2_log_space_left(journal) < nblocks) { write_unlock(&journal->j_state_lock); - mutex_lock(&journal->j_checkpoint_mutex); + mutex_lock_io(&journal->j_checkpoint_mutex); /* * Test again, another process may have checkpointed while we @@ -276,9 +276,22 @@ restart: "JBD2: %s: Waiting for Godot: block %llu\n", journal->j_devname, (unsigned long long) bh->b_blocknr); + if (batch_count) + __flush_batch(journal, &batch_count); jbd2_log_start_commit(journal, tid); + /* + * jbd2_journal_commit_transaction() may want + * to take the checkpoint_mutex if JBD2_FLUSHED + * is set, jbd2_update_log_tail() called by + * jbd2_journal_commit_transaction() may also take + * checkpoint_mutex. So we need to temporarily + * drop it. + */ + mutex_unlock(&journal->j_checkpoint_mutex); jbd2_log_wait_commit(journal, tid); - goto retry; + mutex_lock_io(&journal->j_checkpoint_mutex); + spin_lock(&journal->j_list_lock); + goto restart; } if (!buffer_dirty(bh)) { if (unlikely(buffer_write_io_error(bh)) && !result) |