[PATCH v3 10/15] mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

The last user of gfpflags_allow_spinning() in slab is
alloc_from_pcs_bulk(), which is only called from
kmem_cache_alloc_bulk().

It turns out that gfpflags_allow_spinning() is not necessary, because
kmem_cache_alloc_bulk() is only expected to be called from context that
does allow spinning, so simply replace it with 'true'. This means we can
also drop the gfp parameter from alloc_from_pcs_bulk().

With that, we can remove the "@flags must allow spinning" part of the
kernel doc, as there is no more connection to the gfp flags in the slab
implementation.

Also remove a comment in alloc_slab_obj_exts() because there should be
no more false positives possible due to gfp_allowed_mask during early
boot.

Link: https://patch.msgid.link/20260610-slab_alloc_flags-v2-11-7190909db118@kernel.org
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 562495b80d74..81938774098b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2171,12 +2171,6 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 
 	sz = obj_exts_alloc_size(s, slab, gfp);
 
-	/*
-	 * Note that allow_spin may be false during early boot and its
-	 * restricted GFP_BOOT_MASK. Due to kmalloc_nolock() only supporting
-	 * architectures with cmpxchg16b, early obj_exts will be missing for
-	 * very early allocations on those.
-	 */
 	if (unlikely(!allow_spin))
 		vec = kmalloc_nolock(sz, __GFP_ZERO | __GFP_NO_OBJ_EXT,
 				     slab_nid(slab));
@@ -4830,8 +4824,7 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, unsigned int alloc_flags,
 }
 
 static __fastpath_inline
-unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
-				 void **p)
+unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, size_t size, void **p)
 {
 	struct slub_percpu_sheaves *pcs;
 	struct slab_sheaf *main;
@@ -4866,7 +4859,7 @@ unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
 		}
 
 		full = barn_replace_empty_sheaf(barn, pcs->main,
-						gfpflags_allow_spinning(gfp));
+						/* allow_spin = */ true);
 
 		if (full) {
 			stat(s, BARN_GET);
@@ -7331,8 +7324,7 @@ static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
  * Allocate @size objects from @s and places them into @p.  @size must be larger
  * than 0.
  *
- * Interrupts must be enabled when calling this function and @flags must allow
- * spinning.
+ * Interrupts must be enabled when calling this function.
  *
  * Unlike alloc_pages_bulk(), this function does not check for already allocated
  * objects in @p, and thus the caller does not need to zero it.
@@ -7370,7 +7362,7 @@ bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags,
 		size--;
 	}
 
-	i = alloc_from_pcs_bulk(s, flags, size, p);
+	i = alloc_from_pcs_bulk(s, size, p);
 	if (i < size) {
 		/*
 		 * If we ran out of memory, don't bother with freeing back to

-- 
2.54.0