mm: remove GFP_THISNODE
NOTE: this is not about __GFP_THISNODE, this is only about GFP_THISNODE.
GFP_THISNODE is a secret combination of gfp bits that have different
behavior than expected. It is a combination of __GFP_THISNODE,
__GFP_NORETRY, and __GFP_NOWARN and is special-cased in the page
allocator slowpath to fail without trying reclaim even though it may be
used in combination with __GFP_WAIT.
An example of the problem this creates: commit e97ca8e5b864 ("mm: fix
GFP_THISNODE callers and clarify") fixed up many users of GFP_THISNODE
that really just wanted __GFP_THISNODE. The problem doesn't end there,
however, because even it was a no-op for alloc_misplaced_dst_page(),
which also sets __GFP_NORETRY and __GFP_NOWARN, and
migrate_misplaced_transhuge_page(), where __GFP_NORETRY and __GFP_NOWAIT
is set in GFP_TRANSHUGE. Converting GFP_THISNODE to __GFP_THISNODE is a
no-op in these cases since the page allocator special-cases
__GFP_THISNODE && __GFP_NORETRY && __GFP_NOWARN.
It's time to just remove GFP_THISNODE entirely. We leave __GFP_THISNODE
to restrict an allocation to a local node, but remove GFP_THISNODE and
its obscurity. Instead, we require that a caller clear __GFP_WAIT if it
wants to avoid reclaim.
This allows the aforementioned functions to actually reclaim as they
should. It also enables any future callers that want to do
__GFP_THISNODE but also __GFP_NORETRY && __GFP_NOWARN to reclaim. The
rule is simple: if you don't want to reclaim, then don't set __GFP_WAIT.
Aside: ovs_flow_stats_update() really wants to avoid reclaim as well, so
it is unchanged.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Jarno Rajahalme <jrajahalme@nicira.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab.c b/mm/slab.c
index c4b89ea..7eb38dd 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -857,6 +857,11 @@
return NULL;
}
+static inline gfp_t gfp_exact_node(gfp_t flags)
+{
+ return flags;
+}
+
#else /* CONFIG_NUMA */
static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
@@ -1023,6 +1028,15 @@
return __cache_free_alien(cachep, objp, node, page_node);
}
+
+/*
+ * Construct gfp mask to allocate from a specific node but do not invoke reclaim
+ * or warn about failures.
+ */
+static inline gfp_t gfp_exact_node(gfp_t flags)
+{
+ return (flags | __GFP_THISNODE | __GFP_NOWARN) & ~__GFP_WAIT;
+}
#endif
/*
@@ -2825,7 +2839,7 @@
if (unlikely(!ac->avail)) {
int x;
force_grow:
- x = cache_grow(cachep, flags | GFP_THISNODE, node, NULL);
+ x = cache_grow(cachep, gfp_exact_node(flags), node, NULL);
/* cache_grow can reenable interrupts, then ac could change. */
ac = cpu_cache_get(cachep);
@@ -3019,7 +3033,7 @@
get_node(cache, nid) &&
get_node(cache, nid)->free_objects) {
obj = ____cache_alloc_node(cache,
- flags | GFP_THISNODE, nid);
+ gfp_exact_node(flags), nid);
if (obj)
break;
}
@@ -3047,7 +3061,7 @@
nid = page_to_nid(page);
if (cache_grow(cache, flags, nid, page)) {
obj = ____cache_alloc_node(cache,
- flags | GFP_THISNODE, nid);
+ gfp_exact_node(flags), nid);
if (!obj)
/*
* Another processor may allocate the
@@ -3118,7 +3132,7 @@
must_grow:
spin_unlock(&n->list_lock);
- x = cache_grow(cachep, flags | GFP_THISNODE, nodeid, NULL);
+ x = cache_grow(cachep, gfp_exact_node(flags), nodeid, NULL);
if (x)
goto retry;