ext4: fix deadlock in journal_unmap_buffer()
We cannot wait for transaction commit in journal_unmap_buffer()
because we hold page lock which ranks below transaction start. We
solve the issue by bailing out of journal_unmap_buffer() and
jbd2_journal_invalidatepage() with -EBUSY. Caller is then responsible
for waiting for transaction commit to finish and try invalidation
again. Since the issue can happen only for page stradding i_size, it
is simple enough to manually call jbd2_journal_invalidatepage() for
such page from ext4_setattr(), check the return value and wait if
necessary.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index cd4485d..ddc51a7 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1840,7 +1840,6 @@
BUFFER_TRACE(bh, "entry");
-retry:
/*
* It is safe to proceed here without the j_list_lock because the
* buffers cannot be stolen by try_to_free_buffers as long as we are
@@ -1935,14 +1934,11 @@
* for commit and try again.
*/
if (partial_page) {
- tid_t tid = journal->j_committing_transaction->t_tid;
-
jbd2_journal_put_journal_head(jh);
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
write_unlock(&journal->j_state_lock);
- jbd2_log_wait_commit(journal, tid);
- goto retry;
+ return -EBUSY;
}
/*
* OK, buffer won't be reachable after truncate. We just set
@@ -2003,21 +1999,23 @@
* @page: page to flush
* @offset: length of page to invalidate.
*
- * Reap page buffers containing data after offset in page.
- *
+ * Reap page buffers containing data after offset in page. Can return -EBUSY
+ * if buffers are part of the committing transaction and the page is straddling
+ * i_size. Caller then has to wait for current commit and try again.
*/
-void jbd2_journal_invalidatepage(journal_t *journal,
- struct page *page,
- unsigned long offset)
+int jbd2_journal_invalidatepage(journal_t *journal,
+ struct page *page,
+ unsigned long offset)
{
struct buffer_head *head, *bh, *next;
unsigned int curr_off = 0;
int may_free = 1;
+ int ret = 0;
if (!PageLocked(page))
BUG();
if (!page_has_buffers(page))
- return;
+ return 0;
/* We will potentially be playing with lists other than just the
* data lists (especially for journaled data mode), so be
@@ -2031,9 +2029,11 @@
if (offset <= curr_off) {
/* This block is wholly outside the truncation point */
lock_buffer(bh);
- may_free &= journal_unmap_buffer(journal, bh,
- offset > 0);
+ ret = journal_unmap_buffer(journal, bh, offset > 0);
unlock_buffer(bh);
+ if (ret < 0)
+ return ret;
+ may_free &= ret;
}
curr_off = next_off;
bh = next;
@@ -2044,6 +2044,7 @@
if (may_free && try_to_free_buffers(page))
J_ASSERT(!page_has_buffers(page));
}
+ return 0;
}
/*