From: Vlastimil Babka <vbabka@suse.cz>
To: Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@android.com, vinmenon@codeaurora.org,
Kees Cook <keescook@chromium.org>,
Matthew Garrett <mjg59@google.com>,
Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
Vijayanand Jitta <vjitta@codeaurora.org>
Subject: [RFC PATCH 4/5] mm, slub: make remaining slub_debug related attributes read-only
Date: Tue, 2 Jun 2020 16:15:18 +0200 [thread overview]
Message-ID: <20200602141519.7099-5-vbabka@suse.cz> (raw)
In-Reply-To: <20200602141519.7099-1-vbabka@suse.cz>
SLUB_DEBUG creates several files under /sys/kernel/slab/<cache>/ that can be
read to check if the respective debugging options are enabled for given cache.
Some options, namely sanity_checks, trace, and failslab can be also enabled and
disabled at runtime by writing into the files.
The runtime toggling is racy. Some options disable __CMPXCHG_DOUBLE when
enabled, which means that in case of concurrent allocations, some can still use
__CMPXCHG_DOUBLE and some not, leading to potential corruption. The s->flags
field is also not updated or checked atomically. The simplest solution is to
remove the runtime toggling. The extended slub_debug boot parameter syntax
introduced by earlier patch should allow to fine-tune the debugging
configuration during boot with same granularity.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
Documentation/vm/slub.rst | 7 ++---
mm/slub.c | 62 ++-------------------------------------
2 files changed, 5 insertions(+), 64 deletions(-)
diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
index 61805e984a0d..f240292589bd 100644
--- a/Documentation/vm/slub.rst
+++ b/Documentation/vm/slub.rst
@@ -115,11 +115,8 @@ If the file contains 1, the option is enabled, 0 means disabled. The debug
T trace
A failslab
-The sanity_checks, trace and failslab files are writable, so writing 1 or 0
-will enable or disable the option at runtime. The writes to trace and failslab
-may return -EINVAL if the cache is subject to slab merging. Careful with
-tracing: It may spew out lots of information and never stop if used on the
-wrong slab.
+Careful with tracing: It may spew out lots of information and never stop if
+used on the wrong slab.
Slab merging
============
diff --git a/mm/slub.c b/mm/slub.c
index 58c1e9e7b3b3..38dd6f3ebb04 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5056,20 +5056,6 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
return x + sprintf(buf + x, "\n");
}
-#ifdef CONFIG_SLUB_DEBUG
-static int any_slab_objects(struct kmem_cache *s)
-{
- int node;
- struct kmem_cache_node *n;
-
- for_each_kmem_cache_node(s, node, n)
- if (atomic_long_read(&n->total_objects))
- return 1;
-
- return 0;
-}
-#endif
-
#define to_slab_attr(n) container_of(n, struct slab_attribute, attr)
#define to_slab(n) container_of(n, struct kmem_cache, kobj)
@@ -5291,43 +5277,13 @@ static ssize_t sanity_checks_show(struct kmem_cache *s, char *buf)
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_CONSISTENCY_CHECKS));
}
-
-static ssize_t sanity_checks_store(struct kmem_cache *s,
- const char *buf, size_t length)
-{
- s->flags &= ~SLAB_CONSISTENCY_CHECKS;
- if (buf[0] == '1') {
- s->flags &= ~__CMPXCHG_DOUBLE;
- s->flags |= SLAB_CONSISTENCY_CHECKS;
- }
- return length;
-}
-SLAB_ATTR(sanity_checks);
+SLAB_ATTR_RO(sanity_checks);
static ssize_t trace_show(struct kmem_cache *s, char *buf)
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_TRACE));
}
-
-static ssize_t trace_store(struct kmem_cache *s, const char *buf,
- size_t length)
-{
- /*
- * Tracing a merged cache is going to give confusing results
- * as well as cause other issues like converting a mergeable
- * cache into an umergeable one.
- */
- if (s->refcount > 1)
- return -EINVAL;
-
- s->flags &= ~SLAB_TRACE;
- if (buf[0] == '1') {
- s->flags &= ~__CMPXCHG_DOUBLE;
- s->flags |= SLAB_TRACE;
- }
- return length;
-}
-SLAB_ATTR(trace);
+SLAB_ATTR_RO(trace);
static ssize_t red_zone_show(struct kmem_cache *s, char *buf)
{
@@ -5391,19 +5347,7 @@ static ssize_t failslab_show(struct kmem_cache *s, char *buf)
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_FAILSLAB));
}
-
-static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
- size_t length)
-{
- if (s->refcount > 1)
- return -EINVAL;
-
- s->flags &= ~SLAB_FAILSLAB;
- if (buf[0] == '1')
- s->flags |= SLAB_FAILSLAB;
- return length;
-}
-SLAB_ATTR(failslab);
+SLAB_ATTR_RO(failslab);
#endif
static ssize_t shrink_show(struct kmem_cache *s, char *buf)
--
2.26.2
next prev parent reply other threads:[~2020-06-02 14:16 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-02 14:15 [RFC PATCH 0/5] replace runtime slub_debug toggling with more capable boot parameter Vlastimil Babka
2020-06-02 14:15 ` [RFC PATCH 1/5] mm, slub: extend slub_debug syntax for multiple blocks Vlastimil Babka
2020-06-05 21:06 ` Kees Cook
2020-06-08 16:58 ` Vlastimil Babka
2020-06-02 14:15 ` [RFC PATCH 2/5] mm, slub: make some slub_debug related attributes read-only Vlastimil Babka
2020-06-05 21:06 ` Kees Cook
2020-06-06 0:32 ` Roman Gushchin
2020-06-02 14:15 ` [RFC PATCH 3/5] mm, slub: remove runtime allocation order changes Vlastimil Babka
2020-06-05 21:06 ` Kees Cook
2020-06-06 0:32 ` Roman Gushchin
2020-06-02 14:15 ` Vlastimil Babka [this message]
2020-06-05 21:07 ` [RFC PATCH 4/5] mm, slub: make remaining slub_debug related attributes read-only Kees Cook
2020-06-06 0:33 ` Roman Gushchin
2020-06-02 14:15 ` [RFC PATCH 5/5] mm, slub: make reclaim_account attribute read-only Vlastimil Babka
2020-06-05 21:07 ` Kees Cook
2020-06-06 0:34 ` Roman Gushchin
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