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authorVlastimil Babka <vbabka@suse.cz>2020-08-06 23:19:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 11:33:22 -0700
commitd3c58f24be1bf10fa9e11977080a2398ddcd8361 (patch)
treecc1fe9180c171864baa4b3674f055257d5641cb5 /mm
parent8fc8d6664247a6e65cba000789e2e85e2288f6f7 (diff)
mm, slab/slub: move and improve cache_from_obj()
The function cache_from_obj() was added by commit b9ce5ef49f00 ("sl[au]b: always get the cache from its page in kmem_cache_free()") to support kmemcg, where per-memcg cache can be different from the root one, so we can't use the kmem_cache pointer given to kmem_cache_free(). Prior to that commit, SLUB already had debugging check+warning that could be enabled to compare the given kmem_cache pointer to one referenced by the slab page where the object-to-be-freed resides. This check was moved to cache_from_obj(). Later the check was also enabled for SLAB_FREELIST_HARDENED configs by commit 598a0717a816 ("mm/slab: validate cache membership under freelist hardening"). These checks and warnings can be useful especially for the debugging, which can be improved. Commit 598a0717a816 changed the pr_err() with WARN_ON_ONCE() to WARN_ONCE() so only the first hit is now reported, others are silent. This patch changes it to WARN() so that all errors are reported. It's also useful to print SLUB allocation/free tracking info for the offending object, if tracking is enabled. We could export the SLUB print_tracking() function and provide an empty one for SLAB, or realize that both the debugging and hardening cases in cache_from_obj() are only supported by SLUB anyway. So this patch moves cache_from_obj() from slab.h to separate instances in slab.c and slub.c, where the SLAB version only does the kmemcg lookup and even could be completely removed once the kmemcg rework [1] is merged. The SLUB version can thus easily use the print_tracking() function. It can also use the kmem_cache_debug_flags() static key check for improved performance in kernels without the hardening and with debugging not enabled on boot. [1] https://lore.kernel.org/r/20200608230654.828134-18-guro@fb.com Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Lameter <cl@linux.com> Cc: Jann Horn <jannh@google.com> Cc: Kees Cook <keescook@chromium.org> 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> Link: http://lkml.kernel.org/r/20200610163135.17364-10-vbabka@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/slab.c8
-rw-r--r--mm/slab.h23
-rw-r--r--mm/slub.c21
3 files changed, 29 insertions, 23 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 390e249aaa8d..af3d3887b9b8 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3678,6 +3678,14 @@ void *__kmalloc_track_caller(size_t size, gfp_t flags, unsigned long caller)
}
EXPORT_SYMBOL(__kmalloc_track_caller);
+static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
+{
+ if (memcg_kmem_enabled())
+ return virt_to_cache(x);
+ else
+ return s;
+}
+
/**
* kmem_cache_free - Deallocate an object
* @cachep: The cache the allocation was from.
diff --git a/mm/slab.h b/mm/slab.h
index 58ed025a0b23..a21c78eccee7 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -504,29 +504,6 @@ static __always_inline void uncharge_slab_page(struct page *page, int order,
memcg_uncharge_slab(page, order, s);
}
-static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
-{
- struct kmem_cache *cachep;
-
- /*
- * When kmemcg is not being used, both assignments should return the
- * same value. but we don't want to pay the assignment price in that
- * case. If it is not compiled in, the compiler should be smart enough
- * to not do even the assignment. In that case, slab_equal_or_root
- * will also be a constant.
- */
- if (!memcg_kmem_enabled() &&
- !IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) &&
- !unlikely(s->flags & SLAB_CONSISTENCY_CHECKS))
- return s;
-
- cachep = virt_to_cache(x);
- WARN_ONCE(cachep && !slab_equal_or_root(cachep, s),
- "%s: Wrong slab cache. %s but object is from %s\n",
- __func__, s->name, cachep->name);
- return cachep;
-}
-
static inline size_t slab_ksize(const struct kmem_cache *s)
{
#ifndef CONFIG_SLUB
diff --git a/mm/slub.c b/mm/slub.c
index 0b80a8409836..6a99a3c945cb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1525,6 +1525,10 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
{
return false;
}
+
+static void print_tracking(struct kmem_cache *s, void *object)
+{
+}
#endif /* CONFIG_SLUB_DEBUG */
/*
@@ -3171,6 +3175,23 @@ void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)
}
#endif
+static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
+{
+ struct kmem_cache *cachep;
+
+ if (!IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) &&
+ !memcg_kmem_enabled() &&
+ !kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS))
+ return s;
+
+ cachep = virt_to_cache(x);
+ if (WARN(cachep && !slab_equal_or_root(cachep, s),
+ "%s: Wrong slab cache. %s but object is from %s\n",
+ __func__, s->name, cachep->name))
+ print_tracking(cachep, x);
+ return cachep;
+}
+
void kmem_cache_free(struct kmem_cache *s, void *x)
{
s = cache_from_obj(s, x);