Fix a problem identified by Andrea Arcangeli <andrea@suse.de>
kswapd will set a zone into all_unreclaimable state if it sees that we're not
successfully reclaiming LRU pages. But that fails to notice that we're
successfully reclaiming slab obects, so we can set all_unreclaimable too soon.
So change shrink_slab() to return a success indication if it actually
reclaimed some objects, and don't assume that the zone is all_unreclaimable if
that is true. This means that we won't enter all_unreclaimable state if we
are successfully freeing slab objects but we're not yet actually freeing slab
pages, due to internal fragmentation.
(hm, this has a shortcoming. We could be successfully freeing ZONE_NORMAL
slab objects while being really oom on ZONE_DMA. If that happens then kswapd
might burn a lot of CPU. But given that there might be some slab objects in
ZONE_DMA, perhaps that is appropriate.)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
b15e0905f2