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powerpc/iommu: Use GFP_KERNEL instead of GFP_ATOMIC in iommu_init_table()

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commit 1cf389df09 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@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nishanth Aravamudan 2013-10-01 14:04:53 -07:00 committed by Greg Kroah-Hartman
parent 6b0dcab1d8
commit e6629f1562
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/kernel/iommu.c
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@ -501,7 +501,7 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
/* number of bytes needed for the bitmap */
sz = (tbl->it_size + 7) >> 3;
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);