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SubjectRe: [RFC PATCH] slab: __GFP_NOWARN not being propagated from mempool_alloc()
On Mon, 24 Nov 2008, Miklos Szeredi wrote:
> We see page allocation failure warnings on the mempool_alloc() path.
> See this lkml posting for example:
>
> http://lkml.org/lkml/2008/10/27/100
>
> The cause is that on NUMA, alloc_slabmgmt() clears __GFP_NOWARN,
> together with __GFP_THISNODE and __GFP_NORETRY. But AFAICS it really
> only wants to clear __GFP_THISNODE.
>
> Does this patch looks good?

Yes, it does but looking at mm/slab.c history I think we want something
like the following instead. Christoph?

P.S. First one to test it gets a fabulous prize of a Tested-by tag in the
patch description! How cool is that?

Pekka

From 717b2d7bd2398e948d1dfbd2e83bd6a8403b68da Mon Sep 17 00:00:00 2001
From: Pekka Enberg <penberg@cs.helsinki.fi>
Date: Tue, 25 Nov 2008 00:33:28 +0200
Subject: [PATCH] slab: remove GFP_THISNODE clearing from alloc_slabmgmt()

Commit 6cb062296f73e74768cca2f3eaf90deac54de02d ("Categorize GFP flags")
left one call-site in alloc_slabmgmt() to clear GFP_THISNODE instead of
GFP_CONSTRAINT_MASK. Unfortunately, that ends up clearing __GFP_NOWARN
and __GFP_NORETRY as well which is not what we want. As the only caller
of alloc_slabmgmt() already clears GFP_CONSTRAINT_MASK before passing
local_flags to it, we can just remove the clearing of GFP_THISNODE.

This patch should fix spurious page allocation failure warnings on the
mempool_alloc() path. See the following URL for an example:

http://lkml.org/lkml/2008/10/27/100

Reported-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
mm/slab.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 918f04f..98d3024 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2608,7 +2608,7 @@ static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
if (OFF_SLAB(cachep)) {
/* Slab management obj is off-slab. */
slabp = kmem_cache_alloc_node(cachep->slabp_cache,
- local_flags & ~GFP_THISNODE, nodeid);
+ local_flags, nodeid);
if (!slabp)
return NULL;
} else {
--
1.5.6.4


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