linux-kernel - Re: Slab panic on 2.6.19-rc3-git5 (-git4 was OK)

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Date:	Sun, 29 Oct 2006 04:46:55 -0800 (PST)
From:	Giridhar Pemmasani <pgiri@...oo.com>
To:	Pekka Enberg <penberg@...helsinki.fi>,
	"Martin J. Bligh" <mbligh@...gle.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, Andy Whitcroft <apw@...dowen.org>,
	Linus Torvalds <torvalds@...l.org>, pgiri@...oo.com,
	Andrew Morton <akpm@...l.org>
Subject: Re: Slab panic on 2.6.19-rc3-git5 (-git4 was OK)

--- Pekka Enberg <penberg@...helsinki.fi> wrote:

> Hi,
> 
> On 10/29/06, Martin J. Bligh <mbligh@...gle.com> wrote:
> > -git4 was fine. -git5 is broken (on PPC64 blade)
> >
> > As -rc2-mm2 seemed fine on this box, I'm guessing it's something
> > that didn't go via Andrew ;-( Looks like it might be something
> > JFS or slab specific. Bigger PPC64 box with different config
> > was OK though
> >
> > Full log is here: http://test.kernel.org/abat/59046/debug/console.log
> > Good -git4 run: http://test.kernel.org/abat/58997/debug/console.log
> >
> > kernel BUG in cache_grow at mm/slab.c:2705!
> > cpu 0x1: Vector: 700 (Program Check) at [c0000000fffb7710]
> >      pc: c0000000000c8ad4: .cache_grow+0x64/0x4f0
> >      lr: c0000000000c91a8: .cache_alloc_refill+0x248/0x2cc
> >      sp: c0000000fffb7990
> >     msr: 8000000000021032
> >    current = 0xc0000000fffab800
> >    paca    = 0xc00000000047e780
> >      pid   = 1, comm = swapper
> > kernel BUG in cache_grow at mm/slab.c:2705!
> > enter ? for help
> > [c0000000fffb7a60] c0000000000c91a8 .cache_alloc_refill+0x248/0x2cc
> > [c0000000fffb7b20] c0000000000c9708 .kmem_cache_alloc_node+0xd0/0x10c
> > [c0000000fffb7bc0] c0000000000b69cc .__get_vm_area_node+0xcc/0x230
> > [c0000000fffb7c70] c0000000000b7640 .__vmalloc_node+0x60/0xc0
> > [c0000000fffb7d10] c0000000001ad4c8 .txInit+0x2a0/0x3a8
> > [c0000000fffb7e20] c00000000044c1ec .init_jfs_fs+0x78/0x27c
> > [c0000000fffb7ec0] c0000000000094c0 .init+0x1f4/0x3e4
> > [c0000000fffb7f90] c000000000027270 .kernel_thread+0x4c/0x68
> 
> I only skimmed through this briefly but it looks like due to
> 52fd24ca1db3a741f144bbc229beefe044202cac __get_vm_area_node is passing
> GFP_HIGHMEM to kmem_cache_alloc_node which is a no-no.
> 

I haven't been able to reproduce this, although I understand why it happens:
vmalloc allocates memory with

GFP_KERNEL | __GFP_HIGHMEM

and with git5, the same flags are passed down to cache_alloc_refill, causing
the BUG. The following patch against 2.6.19-rc3-git5 (also attached as
attachment, as this mailer may mess up inline copying) should fix it.

Note that when calling kmalloc_node, I am masking off __GFP_HIGHMEM with
GFP_LEVEL_MASK, whereas __vmalloc_area_node does the same with

~(__GFP_HIGHMEM | __GFP_ZERO).

IMHO, using GFP_LEVEL_MASK is preferable, but either should fix this problem.

Signed-off-by: Giridhar Pemmasani (pgiri@...oo.com)

diff -Naur linux-2.6.19-rc3-git5.orig/mm/vmalloc.c
linux-2.6.19-rc3-git5/mm/vmalloc.c
--- linux-2.6.19-rc3-git5.orig/mm/vmalloc.c     2006-10-29 07:26:34.000000000
-0500
+++ linux-2.6.19-rc3-git5/mm/vmalloc.c  2006-10-29 07:28:12.000000000 -0500
@@ -182,7 +182,7 @@
        addr = ALIGN(start, align);
        size = PAGE_ALIGN(size);

-       area = kmalloc_node(sizeof(*area), gfp_mask, node);
+       area = kmalloc_node(sizeof(*area), gfp_mask & GFP_LEVEL_MASK, node);
        if (unlikely(!area))
                return NULL;


 
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View attachment "__get_vm_area_node-should-mask-off-gfp-highmem.patch" of type "text/x-diff" (487 bytes)