[patch 034/163] mm, slub: introduce kmem_cache_debug_flags()

Andrew Morton
2020-08-07T06:18:58Z

From: Vlastimil Babka <vbabka@suse.cz>
Subject: mm, slub: introduce kmem_cache_debug_flags()

There are few places that call kmem_cache_debug(s) (which tests if any of
debug flags are enabled for a cache) immediately followed by a test for a
specific flag. The compiler can probably eliminate the extra check, but
we can make the code nicer by introducing kmem_cache_debug_flags() that
works like kmem_cache_debug() (including the static key check) but tests
for specific flag(s). The next patches will add more users.

[vbabka@suse.cz: change return from int to bool, per Kees. Add VM_WARN_ON_ONCE() for invalid flags, per Roman]
Link: http://lkml.kernel.org/r/949b90ed-e0f0-07d7-4d21-e30ec0958a7c@suse.cz
Link: http://lkml.kernel.org/r/20200610163135.17364-8-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Jann Horn <jannh@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/slub.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

--- a/mm/slub.c~mm-slub-introduce-kmem_cache_debug_flags
+++ a/mm/slub.c
@@ -122,18 +122,29 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabl
#endif
#endif

-static inline int kmem_cache_debug(struct kmem_cache *s)
+/*
+ * Returns true if any of the specified slub_debug flags is enabled for the
+ * cache. Use only for flags parsed by setup_slub_debug() as it also enables
+ * the static key.
+ */
+static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
{
+ VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS));
#ifdef CONFIG_SLUB_DEBUG
if (static_branch_unlikely(&slub_debug_enabled))
- return s->flags & SLAB_DEBUG_FLAGS;
+ return s->flags & flags;
#endif
- return 0;
+ return false;
+}
+
+static inline bool kmem_cache_debug(struct kmem_cache *s)
+{
+ return kmem_cache_debug_flags(s, SLAB_DEBUG_FLAGS);
}

void *fixup_red_left(struct kmem_cache *s, void *p)
{
- if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
+ if (kmem_cache_debug_flags(s, SLAB_RED_ZONE))
p += s->red_left_pad;

return p;
@@ -4060,7 +4071,7 @@ void __check_heap_object(const void *ptr
offset = (ptr - page_address(page)) % s->size;

/* Adjust for redzone and reject if within the redzone. */
- if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
+ if (kmem_cache_debug_flags(s, SLAB_RED_ZONE)) {
if (offset < s->red_left_pad)
usercopy_abort("SLUB object in left red zone",
s->name, to_user, offset, n);
_