mm: rename alloc_pages_exact_node() to __alloc_pages_node()

alloc_pages_exact_node() was introduced in commit 6484eb3e2a81 ("page
allocator: do not check NUMA node ID when the caller knows the node is
valid") as an optimized variant of alloc_pages_node(), that doesn't
fallback to current node for nid == NUMA_NO_NODE. Unfortunately the
name of the function can easily suggest that the allocation is
restricted to the given node and fails otherwise. In truth, the node is
only preferred, unless __GFP_THISNODE is passed among the gfp flags.

The misleading name has lead to mistakes in the past, see for example
commits 5265047ac301 ("mm, thp: really limit transparent hugepage
allocation to local node") and b360edb43f8e ("mm, mempolicy:
migrate_to_node should only migrate to node").

Another issue with the name is that there's a family of
alloc_pages_exact*() functions where 'exact' means exact size (instead
of page order), which leads to more confusion.

To prevent further mistakes, this patch effectively renames
alloc_pages_exact_node() to __alloc_pages_node() to better convey that
it's an optimized variant of alloc_pages_node() not intended for general
usage. Both functions get described in comments.

It has been also considered to really provide a convenience function for
allocations restricted to a node, but the major opinion seems to be that
__GFP_THISNODE already provides that functionality and we shouldn't
duplicate the API needlessly. The number of users would be small
anyway.

Existing callers of alloc_pages_exact_node() are simply converted to
call __alloc_pages_node(), with the exception of sba_alloc_coherent()
which open-codes the check for NUMA_NO_NODE, so it is converted to use
alloc_pages_node() instead. This means it no longer performs some
VM_BUG_ON checks, and since the current check for nid in
alloc_pages_node() uses a 'nid < 0' comparison (which includes
NUMA_NO_NODE), it may hide wrong values which would be previously
exposed.

Both differences will be rectified by the next patch.

To sum up, this patch makes no functional changes, except temporarily
hiding potentially buggy callers. Restricting the checks in
alloc_pages_node() is left for the next patch which can in turn expose
more existing buggy callers.

Signed-off-by: Vlastimil Babka <[e-mail]>
Acked-by: Johannes Weiner <[e-mail]>
Acked-by: Robin Holt <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Acked-by: Christoph Lameter <[e-mail]>
Acked-by: Michael Ellerman <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Greg Thelen <[e-mail]>
Cc: Aneesh Kumar K.V <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Naoya Horiguchi <[e-mail]>
Cc: Tony Luck <[e-mail]>
Cc: Fenghua Yu <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Gleb Natapov <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Cliff Whickman <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/ia64/hp/common/sba_iommu.c

···
 
 #ifdef CONFIG_NUMA
 	{
-		int node = ioc->node;
 		struct page *page;
 
-		if (node == NUMA_NO_NODE)
-			node = numa_node_id();
-
-		page = alloc_pages_exact_node(node, flags, get_order(size));
+		page = alloc_pages_node(ioc->node, flags, get_order(size));
 		if (unlikely(!page))
 			return NULL;
 

arch/ia64/kernel/uncached.c

···
 
 	/* attempt to allocate a granule's worth of cached memory pages */
 
-	page = alloc_pages_exact_node(nid,
+	page = __alloc_pages_node(nid,
 				GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
 				IA64_GRANULE_SHIFT-PAGE_SHIFT);
 	if (!page) {

arch/ia64/sn/pci/pci_dma.c

···
 	 */
 	node = pcibus_to_node(pdev->bus);
 	if (likely(node >=0)) {
-		struct page *p = alloc_pages_exact_node(node,
+		struct page *p = __alloc_pages_node(node,
 						flags, get_order(size));
 
 		if (likely(p))

arch/powerpc/platforms/cell/ras.c

···
 
 	area->nid = nid;
 	area->order = order;
-	area->pages = alloc_pages_exact_node(area->nid,
+	area->pages = __alloc_pages_node(area->nid,
 						GFP_KERNEL|__GFP_THISNODE,
 						area->order);
 

arch/x86/kvm/vmx.c

···
 	struct page *pages;
 	struct vmcs *vmcs;
 
-	pages = alloc_pages_exact_node(node, GFP_KERNEL, vmcs_config.order);
+	pages = __alloc_pages_node(node, GFP_KERNEL, vmcs_config.order);
 	if (!pages)
 		return NULL;
 	vmcs = page_address(pages);

drivers/misc/sgi-xp/xpc_uv.c

···
 	mq->mmr_blade = uv_cpu_to_blade_id(cpu);
 
 	nid = cpu_to_node(cpu);
-	page = alloc_pages_exact_node(nid,
+	page = __alloc_pages_node(nid,
 				      GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
 				      pg_order);
 	if (page == NULL) {

include/linux/gfp.h

···
 	return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL);
 }
 
+/*
+ * Allocate pages, preferring the node given as nid. The node must be valid and
+ * online. For more general interface, see alloc_pages_node().
+ */
+static inline struct page *
+__alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
+{
+	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES || !node_online(nid));
+
+	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
+}
+
+/*
+ * Allocate pages, preferring the node given as nid. When nid == NUMA_NO_NODE,
+ * prefer the current CPU's node.
+ */
 static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
 						unsigned int order)
 {
 	/* Unknown node is current node */
 	if (nid < 0)
 		nid = numa_node_id();
-
-	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
-}
-
-static inline struct page *alloc_pages_exact_node(int nid, gfp_t gfp_mask,
-						unsigned int order)
-{
-	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES || !node_online(nid));
 
 	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
 }
···
 
 void *alloc_pages_exact(size_t size, gfp_t gfp_mask);
 void free_pages_exact(void *virt, size_t size);
-/* This is different from alloc_pages_exact_node !!! */
 void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask);
 
 #define __get_free_page(gfp_mask) \

kernel/profile.c

···
 		node = cpu_to_mem(cpu);
 		per_cpu(cpu_profile_flip, cpu) = 0;
 		if (!per_cpu(cpu_profile_hits, cpu)[1]) {
-			page = alloc_pages_exact_node(node,
+			page = __alloc_pages_node(node,
 					GFP_KERNEL | __GFP_ZERO,
 					0);
 			if (!page)
···
 			per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 		}
 		if (!per_cpu(cpu_profile_hits, cpu)[0]) {
-			page = alloc_pages_exact_node(node,
+			page = __alloc_pages_node(node,
 					GFP_KERNEL | __GFP_ZERO,
 					0);
 			if (!page)
···
 		int node = cpu_to_mem(cpu);
 		struct page *page;
 
-		page = alloc_pages_exact_node(node,
+		page = __alloc_pages_node(node,
 				GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
 				0);
 		if (!page)
 			goto out_cleanup;
 		per_cpu(cpu_profile_hits, cpu)[1]
 				= (struct profile_hit *)page_address(page);
-		page = alloc_pages_exact_node(node,
+		page = __alloc_pages_node(node,
 				GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
 				0);
 		if (!page)

mm/filemap.c

···
 		do {
 			cpuset_mems_cookie = read_mems_allowed_begin();
 			n = cpuset_mem_spread_node();
-			page = alloc_pages_exact_node(n, gfp, 0);
+			page = __alloc_pages_node(n, gfp, 0);
 		} while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
 
 		return page;

mm/huge_memory.c

···
 	 */
 	up_read(&mm->mmap_sem);
 
-	*hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER);
+	*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
 	if (unlikely(!*hpage)) {
 		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
 		*hpage = ERR_PTR(-ENOMEM);

mm/hugetlb.c

···
 {
 	struct page *page;
 
-	page = alloc_pages_exact_node(nid,
+	page = __alloc_pages_node(nid,
 		htlb_alloc_mask(h)|__GFP_COMP|__GFP_THISNODE|
 						__GFP_REPEAT|__GFP_NOWARN,
 		huge_page_order(h));
···
 				   __GFP_REPEAT|__GFP_NOWARN,
 				   huge_page_order(h));
 	else
-		page = alloc_pages_exact_node(nid,
+		page = __alloc_pages_node(nid,
 			htlb_alloc_mask(h)|__GFP_COMP|__GFP_THISNODE|
 			__GFP_REPEAT|__GFP_NOWARN, huge_page_order(h));
 

mm/memory-failure.c

···
 		return alloc_huge_page_node(page_hstate(compound_head(p)),
 						   nid);
 	else
-		return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
+		return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);
 }
 
 /*

mm/mempolicy.c

···
 		return alloc_huge_page_node(page_hstate(compound_head(page)),
 					node);
 	else
-		return alloc_pages_exact_node(node, GFP_HIGHUSER_MOVABLE |
+		return __alloc_pages_node(node, GFP_HIGHUSER_MOVABLE |
 						    __GFP_THISNODE, 0);
 }
 
···
 		nmask = policy_nodemask(gfp, pol);
 		if (!nmask || node_isset(hpage_node, *nmask)) {
 			mpol_cond_put(pol);
-			page = alloc_pages_exact_node(hpage_node,
+			page = __alloc_pages_node(hpage_node,
 						gfp | __GFP_THISNODE, order);
 			goto out;
 		}

mm/migrate.c

···
 		return alloc_huge_page_node(page_hstate(compound_head(p)),
 					pm->node);
 	else
-		return alloc_pages_exact_node(pm->node,
+		return __alloc_pages_node(pm->node,
 				GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
 }
 
···
 	int nid = (int) data;
 	struct page *newpage;
 
-	newpage = alloc_pages_exact_node(nid,
+	newpage = __alloc_pages_node(nid,
 					 (GFP_HIGHUSER_MOVABLE |
 					  __GFP_THISNODE | __GFP_NOMEMALLOC |
 					  __GFP_NORETRY | __GFP_NOWARN) &

mm/page_alloc.c

···
  *
  * Like alloc_pages_exact(), but try to allocate on node nid first before falling
  * back.
- * Note this is not alloc_pages_exact_node() which allocates on a specific node,
- * but is not exact.
  */
 void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
 {

mm/slab.c

···
 	if (memcg_charge_slab(cachep, flags, cachep->gfporder))
 		return NULL;
 
-	page = alloc_pages_exact_node(nodeid, flags | __GFP_NOTRACK, cachep->gfporder);
+	page = __alloc_pages_node(nodeid, flags | __GFP_NOTRACK, cachep->gfporder);
 	if (!page) {
 		memcg_uncharge_slab(cachep, cachep->gfporder);
 		slab_out_of_memory(cachep, flags, nodeid);

mm/slob.c

···
  * NUMA support in SLOB is fairly simplistic, pushing most of the real
  * logic down to the page allocator, and simply doing the node accounting
  * on the upper levels. In the event that a node id is explicitly
- * provided, alloc_pages_exact_node() with the specified node id is used
+ * provided, __alloc_pages_node() with the specified node id is used
  * instead. The common case (or when the node id isn't explicitly provided)
  * will default to the current node, as per numa_node_id().
  *
···
 
 #ifdef CONFIG_NUMA
 	if (node != NUMA_NO_NODE)
-		page = alloc_pages_exact_node(node, gfp, order);
+		page = __alloc_pages_node(node, gfp, order);
 	else
 #endif
 		page = alloc_pages(gfp, order);

mm/slub.c

···
 	if (node == NUMA_NO_NODE)
 		page = alloc_pages(flags, order);
 	else
-		page = alloc_pages_exact_node(node, flags, order);
+		page = __alloc_pages_node(node, flags, order);
 
 	if (!page)
 		memcg_uncharge_slab(s, order);