tree 93e49d6e383d3ababfd7733aad9543566f0a681c
parent d1211af3049f4c9c1d8d4eb8f8098cc4f4f0d0c7
author Nishanth Aravamudan <nacc@linux.vnet.ibm.com> 1380661493 -0700
committer Benjamin Herrenschmidt <benh@kernel.crashing.org> 1380785084 +1000

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

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>
CC: <stable@vger.kernel.org>