On Mon 29-02-16 16:08:00, Tejun Heo wrote:

On Mon, Feb 29, 2016 at 09:06:15PM +0000, Al Viro wrote:

quoted

quoted

Hmmm?  The flushing is done after shrink_dcache_for_umount() and
sync_filesystems().  Aren't inodes supposed to stay clean after that?

s/shrink_dcache_for_umount/fsnotify_unmount_inodes/ - sorry.

Is that allowed to dirty indoes and initiate writebacks again, after
sync_filesystems() is done?  That sounds weird but it's trivial to
move cgroup_writeback_umount() below that if so.

Hardly, but generally it is true that filesystem may still dirty something
(e.g. from outstanding workqueue work, but most likely some special "system
inodes" may still become dirty) until ->put_super() is finished.

Anyway, to make this foolproof, I'd just avoid queueing any new switching
work after S_ACTIVE is cleared on the superblock and flush the workqueue just
before evict_inodes() call.

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR