2019-08-05 04:10:50

by Chandan Rajendra

Subject: [PATCH V2] jbd2: flush_descriptor(): Do not decrease buffer head's ref count

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 <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Chandan Rajendra <[email protected]>
---
Changelog:
V1 -> V2:
1. Fix commit message.

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 69b9bc329964..f08073d7bbf5 100644
--- a/fs/jbd2/revoke.c
+++ b/fs/jbd2/revoke.c
@@ -638,10 +638,8 @@ 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);
--
2.19.1

2019-08-08 15:52:03

by Theodore Ts'o

Subject: Re: [PATCH V2] jbd2: flush_descriptor(): Do not decrease buffer head's ref count

On Mon, Aug 05, 2019 at 09:38:00AM +0530, Chandan Rajendra wrote:
> 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 <[email protected]>
> Reviewed-by: Jan Kara <[email protected]>
> Signed-off-by: Chandan Rajendra <[email protected]>

Thanks, applied.

- Ted