[PATCH AUTOSEL 4.9 14/20] jbd2: flush_descriptor(): Do not decrease buffer head's ref count

Sasha Levin
2019-10-25T14:01:05Z

From: Chandan Rajendra <chandan@linux.ibm.com>

[ Upstream commit 547b9ad698b434eadca46319cb47e5875b55ef03 ]

When executing generic/388 on a ppc64le machine, we notice the following
call trace,

VFS: brelse: Trying to free free buffer
WARNING: CPU: 0 PID: 6637 at /root/repos/linux/fs/buffer.c:1195 __brelse+0x84/0xc0

Call Trace:
__brelse+0x80/0xc0 (unreliable)
invalidate_bh_lru+0x78/0xc0
on_each_cpu_mask+0xa8/0x130
on_each_cpu_cond_mask+0x130/0x170
invalidate_bh_lrus+0x44/0x60
invalidate_bdev+0x38/0x70
ext4_put_super+0x294/0x560
generic_shutdown_super+0xb0/0x170
kill_block_super+0x38/0xb0
deactivate_locked_super+0xa4/0xf0
cleanup_mnt+0x164/0x1d0
task_work_run+0x110/0x160
do_notify_resume+0x414/0x460
ret_from_except_lite+0x70/0x74

The warning happens because flush_descriptor() drops bh reference it
does not own. The bh reference acquired by
jbd2_journal_get_descriptor_buffer() is owned by the log_bufs list and
gets released when this list is processed. The reference for doing IO is
only acquired in write_dirty_buffer() later in flush_descriptor().

Reported-by: Harish Sriram <harish@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/jbd2/revoke.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/jbd2/revoke.c b/fs/jbd2/revoke.c
index 3cd73059da9a4..bf2e164d341aa 100644
--- a/fs/jbd2/revoke.c
+++ b/fs/jbd2/revoke.c
@@ -637,10 +637,8 @@ static void flush_descriptor(journal_t *journal,
{
jbd2_journal_revoke_header_t *header;

- if (is_journal_aborted(journal)) {
- put_bh(descriptor);
+ if (is_journal_aborted(journal))
return;
- }

header = (jbd2_journal_revoke_header_t *)descriptor->b_data;
header->r_count = cpu_to_be32(offset);
--
2.20.1