From patchwork Thu Aug 25 13:49:56 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: fs / ext3: Always unlock updates in ext3_freeze() From: Pavel Machek X-Patchwork-Id: 111573 Message-Id: <20110825134956.GA10476@ucw.cz> To: "Rafael J. Wysocki" Cc: Dave Chinner , Jan Kara , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, LKML Date: Thu, 25 Aug 2011 15:49:56 +0200 Hi! > > > > The problem really isn't XFS specific, nor is it new - the fact is > > > > that any filesystem that has registered a shrinker or can do async > > > > work in the background post-sync is vulnerable to this problem. It's > > > > > > Should we avoid calling shrinkers while hibernating? > > > > If you like getting random OOM problems when hibernating, then go > > for it. Besides, shrinkers are used for more than just filesystems, > > so you might find you screw entire classes of users by doing this > > (eg everyone using intel graphics and 3D). > > > > > Or put BUG_ON()s into filesystem shrinkers so that this can not > > > happen? > > > > Definitely not. If your concern is filesystem shrinkers and you want > > a large hammer to hit the problem with then do your hibernate > > image allocation wih GFP_NOFS and the filesystem shrinkers will > > abort without doing anything. > > I think we can do that, actually. I believe we should, yes. Question is if it helps much, because various drivers (and userspace in case uswsusp?) will still trigger GFP_KERNEL allocations. Something like this? --- snapshot.c.ofic 2011-08-25 15:48:41.000000000 +0200 +++ snapshot.c 2011-08-25 15:49:07.000000000 +0200 @@ -1107,7 +1107,7 @@ /* Helper functions used for the shrinking of memory. */ -#define GFP_IMAGE (GFP_KERNEL | __GFP_NOWARN) +#define GFP_IMAGE (GFP_NODS | __GFP_NOWARN) /** * preallocate_image_pages - Allocate a number of pages for hibernation image