[PATCH 1/3] jbd2: protect buffers release with j_checkpoint_mutex

[Zhang Yi <yi.zhang@xxxxxxxxxx>]

There is a race between jbd2_journal_try_to_free_buffers() and
jbd2_journal_destroy(), so the jbd2_log_do_checkpoint() may still
missing to detect the buffer write io error flag and lead to filesystem
inconsistency.

jbd2_journal_try_to_free_buffers()     ext4_put_super()
                                        jbd2_journal_destroy()
  __jbd2_journal_remove_checkpoint()
  detect buffer write error              jbd2_log_do_checkpoint()
                                         jbd2_cleanup_journal_tail()
                                           <--- lead to inconsistency
  jbd2_journal_abort()

Fix this issue by add j_checkpoint_mutex to protect journal buffer
release on jbd2_journal_try_to_free_buffers().

Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 fs/jbd2/transaction.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 9396666b7314..b935b20cbae4 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -2123,6 +2123,7 @@ int jbd2_journal_try_to_free_buffers(journal_t *journal, struct page *page)
 
 	J_ASSERT(PageLocked(page));
 
+	mutex_lock(&journal->j_checkpoint_mutex);
 	head = page_buffers(page);
 	bh = head;
 	do {
@@ -2163,6 +2164,7 @@ int jbd2_journal_try_to_free_buffers(journal_t *journal, struct page *page)
 	if (has_write_io_error)
 		jbd2_journal_abort(journal, -EIO);
 
+	mutex_unlock(&journal->j_checkpoint_mutex);
 	return ret;
 }
 
-- 
2.25.4