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 <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Robin Holt <robinmholt@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Cliff Whickman <cpw@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

10 files changed, 13 insertions, 15 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 30d69c0c5a38..72940fb38666 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -674,7 +674,7 @@ struct page *__page_cache_alloc(gfp_t gfp)
 		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;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 71a4822c832b..883f613ada7e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2414,7 +2414,7 @@ khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
 	 */
 	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);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index cd1280c487ff..999fb0aef8f1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1331,7 +1331,7 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
 {
 	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));
@@ -1483,7 +1483,7 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
 				   __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));
 
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index bba2d7c2c9ce..eeda6485e76c 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1521,7 +1521,7 @@ static struct page *new_page(struct page *p, unsigned long private, int **x)
 		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);
 }
 
 /*
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d6f2caee28c0..87a177917cb2 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -942,7 +942,7 @@ static struct page *new_node_page(struct page *page, unsigned long node, int **x
 		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);
 }
 
@@ -1998,7 +1998,7 @@ retry_cpuset:
 		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;
 		}
diff --git a/mm/migrate.c b/mm/migrate.c
index 918defbdda0e..02ce25df16c2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1195,7 +1195,7 @@ static struct page *new_page_node(struct page *p, unsigned long private,
 		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);
 }
 
@@ -1555,7 +1555,7 @@ static struct page *alloc_misplaced_dst_page(struct page *page,
 	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) &
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 252665d553b4..bdaa0cf8fd41 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3511,8 +3511,6 @@ EXPORT_SYMBOL(alloc_pages_exact);
  *
  * 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)
 {
diff --git a/mm/slab.c b/mm/slab.c
index 60c936938b84..c77ebe6cc87c 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1595,7 +1595,7 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
 	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);
diff --git a/mm/slob.c b/mm/slob.c
index 165bbd3cd606..0d7e5df74d1f 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -45,7 +45,7 @@
  * 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().
  *
@@ -193,7 +193,7 @@ static void *slob_new_pages(gfp_t gfp, int order, int node)
 
 #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);
diff --git a/mm/slub.c b/mm/slub.c
index 084184e706c6..f614b5dc396b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1334,7 +1334,7 @@ static inline struct page *alloc_slab_page(struct kmem_cache *s,
 	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);