Re: frequent softlockups with 3.10rc6.

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, Jul 2, 2013 at 7:05 AM, Jan Kara <jack@suse.cz> wrote:
> On Tue 02-07-13 22:38:35, Dave Chinner wrote:
>>
>> IOWs, sync is 7-8x faster on a busy filesystem and does not have an
>> adverse impact on ongoing async data write operations.
>   The patch looks good. You can add:
> Reviewed-by: Jan Kara <jack@suse.cz>

Ok, I'm going to take this patch asap. Should we also mark it for
stable? It doesn't look like a regression in that particular code, but
it sounds like it might be a regression when paired with the way the
flusher threads interact. Or is this really some long-time performance
problem?

I'm also wondering if we should just change all callers - remove that
"wait for writeback to complete" from writeback_one_inode()
completely, and just make sure that *all* callers that use WB_SYNC_ALL
do the "wait for writeback" in a separate stage, the way "sync()"
already does? That whole

        if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {

test doesn't really look all that sane (..so thanks Dave for adding a
comment above it)

               Linus