This is a note to let you know that I've just added the patch titled
powerpc/iommu: Use GFP_KERNEL instead of GFP_ATOMIC in iommu_init_table()
to the 3.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-iommu-use-gfp_kernel-instead-of-gfp_atomic-in-iommu_init_table.patch
and it can be found in the queue-3.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1cf389df090194a0976dc867b7fffe99d9d490cb Mon Sep 17 00:00:00 2001
From: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
Date: Tue, 1 Oct 2013 14:04:53 -0700
Subject: powerpc/iommu: Use GFP_KERNEL instead of GFP_ATOMIC in iommu_init_table()
From: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
commit 1cf389df090194a0976dc867b7fffe99d9d490cb upstream.
Under heavy (DLPAR?) stress, we tripped this panic() in
arch/powerpc/kernel/iommu.c::iommu_init_table():
page = alloc_pages_node(nid, GFP_ATOMIC, get_order(sz));
if (!page)
panic("iommu_init_table: Can't allocate %ld bytes\n", sz);
Before the panic() we got a page allocation failure for an order-2
allocation. There appears to be memory free, but perhaps not in the
ATOMIC context. I looked through all the call-sites of
iommu_init_table() and didn't see any obvious reason to need an ATOMIC
allocation. Most call-sites in fact have an explicit GFP_KERNEL
allocation shortly before the call to iommu_init_table(), indicating we
are not in an atomic context. There is some indirection for some paths,
but I didn't see any locks indicating that GFP_KERNEL is inappropriate.
With this change under the same conditions, we have not been able to
reproduce the panic.
Signed-off-by: Nishanth Aravamudan <nacc@xxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/iommu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -661,7 +661,7 @@ struct iommu_table *iommu_init_table(str
/* number of bytes needed for the bitmap */
sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
- page = alloc_pages_node(nid, GFP_ATOMIC, get_order(sz));
+ page = alloc_pages_node(nid, GFP_KERNEL, get_order(sz));
if (!page)
panic("iommu_init_table: Can't allocate %ld bytes\n", sz);
tbl->it_map = page_address(page);
Patches currently in stable-queue which might be from nacc@xxxxxxxxxxxxxxxxxx are
queue-3.11/powerpc-iommu-use-gfp_kernel-instead-of-gfp_atomic-in-iommu_init_table.patch
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