[PATCH] SLUB: Don't drop __GFP_NOFAIL completely fromallocate_slab() (was: Re: [Bug #14265] ifconfig: page allocationfailure. order:5,ode:0x8020 w/ e100)

[Karol Lewandowski]

On Thu, Oct 01, 2009 at 09:56:04PM +0200, Rafael J. Wysocki wrote:
> Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=14265
> Subject		: ifconfig: page allocation failure. order:5, mode:0x8020 w/ e100
> Submitter	: Karol Lewandowski <karol.k.lewandowski@xxxxxxxxx>
> Date		: 2009-09-15 12:05 (17 days old)
> References	: http://marc.info/?l=linux-kernel&m=125301636509517&w=4

Guys, could anyone check if patch below helps?  I think I've finally
found culprit of all allocation failures (but I might be wrong
too... ;-)

Thanks.


commit d6849591e042bceb66f1b4513a1df6740d2ad762
Author: Karol Lewandowski <karol.k.lewandowski@xxxxxxxxx>
Date:   Wed Oct 21 21:01:20 2009 +0200

    SLUB: Don't drop __GFP_NOFAIL completely from allocate_slab()
    
    Commit ba52270d18fb17ce2cf176b35419dab1e43fe4a3 unconditionally
    cleared __GFP_NOFAIL flag on all allocations.
    
    Preserve this flag on second attempt to allocate page (with possibly
    decreased order).
    
    This should help with bugs #14265, #14141 and similar.
    
    Signed-off-by: Karol Lewandowski <karol.k.lewandowski@xxxxxxxxx>

diff --git a/mm/slub.c b/mm/slub.c
index b627675..ac5db65 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1084,7 +1084,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 {
 	struct page *page;
 	struct kmem_cache_order_objects oo = s->oo;
-	gfp_t alloc_gfp;
+	gfp_t alloc_gfp, nofail;
 
 	flags |= s->allocflags;
 
@@ -1092,6 +1092,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	 * Let the initial higher-order allocation fail under memory pressure
 	 * so we fall-back to the minimum order allocation.
 	 */
+	nofail = flags & __GFP_NOFAIL;
 	alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
 
 	page = alloc_slab_page(alloc_gfp, node, oo);
@@ -1100,8 +1101,10 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 		/*
 		 * Allocation may have failed due to fragmentation.
 		 * Try a lower order alloc if possible
+		 *
+		 * Preserve __GFP_NOFAIL flag if previous allocation failed.
 		 */
-		page = alloc_slab_page(flags, node, oo);
+		page = alloc_slab_page(flags | nofail, node, oo);
 		if (!page)
 			return NULL;
 
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