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authorXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>2019-01-31 23:42:11 -0500
committerTheodore Ts'o <tytso@mit.edu>2019-01-31 23:42:11 -0500
commit53cf978457325d8fb2cdecd7981b31a8229e446e (patch)
treef090389c633b762bdcfe55aafa796fc46dc06cbb /fs/jbd2/checkpoint.c
parent8fdd60f2ae3682caf2a7258626abc21eb4711892 (diff)
downloadlinux-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.c17
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)