On Mon, Aug 22, 2011 at 04:38:21PM -0700, Andrew Morton wrote: > On Tue, 23 Aug 2011 09:22:57 +1000 > Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > > On Mon, Aug 22, 2011 at 02:17:21PM +0300, Konstantin Khlebnikov wrote: > > > Shrinker function can returns -1, it means it cannot do anything without a risk of deadlock. > > > For example prune_super() do this if it cannot grab superblock refrence, even if nr_to_scan=0. > > > Currenly we interpret this like ULONG_MAX size shrinker, evaluate total_scan according this, > > > and next time this shrinker can get really big pressure. Let's skip such shrinkers instead. > > > > > > Also make total_scan signed, otherwise check (total_scan < 0) below never works. > > > > I've got a patch set I am going to post out today that makes this > > irrelevant. > > Well, how serious is the bug? If it's a non-issue then we can leave > the fix until 3.1. If it's a non-non-issue then we'd need a minimal > patch to fix up 3.1 and 3.0.x. I'm pretty sure it's a non-issue. I'm pretty sure all of the shrinkers return a count >= 0 rather than -1 when passed nr_to_scan == 0 (i.e. they skip the GFP_NOFS checking), so getting a max_pass of -1 isn't going to happen very often.... And with total_scan being unsigned, the negative check is followed by a "if (total_scan > max_pass * 2)" check, which will catch numbers that would have gone negative anyway because max_pass won't be negative.... So, grotty code but I don't think there is even a problem that can be tripped right now. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>