[PATCH RFC 07/15] mm/slab: pass alloc_flags to new slab allocation

[Vlastimil Babka (SUSE)]

Add the alloc_flags parameter to allocate_slab() and new_slab()
so it can be used to determine if spinning is allowed, independently
from gfp flags.

refill_objects() passes SLAB_ALLOC_DEFAULT because it can only be
reached from contexts that allow spinning.

Also change how trynode_flags are constructed in ___slab_alloc() to
achieve the same "do not upgrade to GFP_NOWAIT" by using masking instead
of a branch. It will now also not upgrade in cases where gfp is weaker
than GFP_NOWAIT (i.e. lacks __GFP_KSWAPD_RECLAIM) but doesn't come from
kmalloc_nolock() - which is more correct anyway.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>
---
 mm/slub.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 0bde4f6d9126..20df6b131f63 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3378,9 +3378,10 @@ static __always_inline void unaccount_slab(struct slab *slab, int order,
 }
 
 /* Allocate and initialize a slab without building its freelist. */
-static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
+static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,
+				  unsigned int alloc_flags, int node)
 {
-	bool allow_spin = gfpflags_allow_spinning(flags);
+	bool allow_spin = alloc_flags_allow_spinning(alloc_flags);
 	struct slab *slab;
 	struct kmem_cache_order_objects oo = s->oo;
 	gfp_t alloc_gfp;
@@ -3438,15 +3439,17 @@ static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	return slab;
 }
 
-static struct slab *new_slab(struct kmem_cache *s, gfp_t flags, int node)
+static struct slab *new_slab(struct kmem_cache *s, gfp_t flags,
+			     unsigned int alloc_flags, int node)
 {
 	if (unlikely(flags & GFP_SLAB_BUG_MASK))
 		flags = kmalloc_fix_flags(flags);
 
 	WARN_ON_ONCE(s->ctor && (flags & __GFP_ZERO));
 
-	return allocate_slab(s,
-		flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
+	flags &= GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK;
+
+	return allocate_slab(s, flags, alloc_flags, node);
 }
 
 static void __free_slab(struct kmem_cache *s, struct slab *slab, bool allow_spin)
@@ -4467,25 +4470,22 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	 * 1) try to get a partial slab from target node only by having
 	 *    __GFP_THISNODE in pc.flags for get_from_partial()
 	 * 2) if 1) failed, try to allocate a new slab from target node with
-	 *    GPF_NOWAIT | __GFP_THISNODE opportunistically
+	 *    (at most) GPF_NOWAIT | __GFP_THISNODE opportunistically
 	 * 3) if 2) failed, retry with original gfpflags which will allow
 	 *    get_from_partial() try partial lists of other nodes before
 	 *    potentially allocating new page from other nodes
 	 */
 	if (unlikely(node != NUMA_NO_NODE && !(gfpflags & __GFP_THISNODE)
 		     && try_thisnode)) {
-		if (unlikely(!allow_spin))
-			/* Do not upgrade gfp to NOWAIT from more restrictive mode */
-			trynode_flags = gfpflags | __GFP_THISNODE;
-		else
-			trynode_flags = GFP_NOWAIT | __GFP_THISNODE;
+		trynode_flags &= GFP_NOWAIT;
+		trynode_flags |= __GFP_NOWARN | __GFP_THISNODE;
 	}
 
 	object = get_from_partial(s, node, trynode_flags, ac);
 	if (object)
 		goto success;
 
-	slab = new_slab(s, trynode_flags, node);
+	slab = new_slab(s, trynode_flags, ac->alloc_flags, node);
 
 	if (unlikely(!slab)) {
 		if (node != NUMA_NO_NODE && !(gfpflags & __GFP_THISNODE)
@@ -7215,7 +7215,7 @@ refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min,
 
 new_slab:
 
-	slab = new_slab(s, gfp, local_node);
+	slab = new_slab(s, gfp, SLAB_ALLOC_DEFAULT, local_node);
 	if (!slab)
 		goto out;
 
@@ -7563,7 +7563,7 @@ static void early_kmem_cache_node_alloc(int node)
 
 	BUG_ON(kmem_cache_node->size < sizeof(struct kmem_cache_node));
 
-	slab = new_slab(kmem_cache_node, GFP_NOWAIT, node);
+	slab = new_slab(kmem_cache_node, GFP_NOWAIT, SLAB_ALLOC_DEFAULT, node);
 
 	BUG_ON(!slab);
 	if (slab_nid(slab) != node) {

-- 
2.54.0