writeback-do-not-sync-data-dirtied-after-sync-start-fix-2.txt

writeback-do-not-sync-data-dirtied-after-sync-start-fix-2.txt

On Wed 09-10-13 14:21:25, Andrew Morton wrote:
> On Wed, 9 Oct 2013 17:03:25 +0200 Jan Kara <jack@suse.cz> wrote:
>
> > From: Jan Kara <jack@suse.cz>
> > Date: Wed, 9 Oct 2013 15:41:50 +0200
> > Subject: [PATCH] writeback: Use older_than_this_is_set instead of magic
> >  older_than_this == 0
> >
> > Currently we use 0 as a special value of work->older_than_this to
> > indicate that wb_writeback() should set work->older_that_this to current
> > time. This works but it is a bit magic. So use a special flag in
> > work_struct for that.
>
> OK.
>
> > -	if (!work->older_than_this)
> > +	if (!work->older_than_this_is_set)
> > 		work->older_than_this = jiffies;
>
> It would be logical although presumably unneeded to set
> older_than_this_is_set here?
  Yes. Updated.

> > Also fixup writeback from workqueue rescuer to include all inodes.
>
> There's nothing in the patch which matches this sentence?
  The sentence is about the hunk below. writeback_inodes_wb() is special in
that it directly calls queue_io() (everything else goes through
wb_writeback()) and my previous patch thus resulted in using 0 as an
older_than_this value => likely we wouldn't queue any inodes for writeback.

I've added WARN_ON_ONCE into move_expired_inodes() to increase a chance of
catching such mistakes in future (although in this particular case it
wouldn't really help because writeback_inodes_wb() gets hardly ever
called).

Currently we use 0 as a special value of work->older_than_this to
indicate that wb_writeback() should set work->older_that_this to current
time. This works but it is a bit magic. So use a special flag in
work_struct for that.

Also fixup writeback from workqueue rescuer (writeback_inodes_wb()) to
include all inodes. Currently it would use 0 as an older_than_this value
thus queue_io() would likely not queue any inodes for writeback.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>