• Nishanth Aravamudan's avatar
    powerpc/iommu: Use GFP_KERNEL instead of GFP_ATOMIC in iommu_init_table() · 1cf389df
    Nishanth Aravamudan authored
    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: default avatarNishanth Aravamudan <nacc@us.ibm.com>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    CC: <stable@vger.kernel.org>
    1cf389df
iommu.c 29.4 KB