From: Miles Chen <miles.chen@xxxxxxxxxxxx>
When debugging slab errors in slub.c, sometimes we have to trigger
a panic in order to get the coredump file. Add a debug option
SLAB_WARN_ON_ERROR to toggle WARN_ON() when the option is set.
Change since v1:
1. Add a special debug option SLAB_WARN_ON_ERROR and toggle WARN_ON()
if it is set.
2. SLAB_WARN_ON_ERROR can be set by kernel parameter slub_debug.
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>,
Cc: David Rientjes <rientjes@xxxxxxxxxx>,
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>,
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx>
---
Documentation/vm/slub.rst | 1 +
include/linux/slab.h | 3 +++
mm/slub.c | 34 ++++++++++++++++++++++++++++++++--
3 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
index 195928808bac..236c00b2d17b 100644
--- a/Documentation/vm/slub.rst
+++ b/Documentation/vm/slub.rst
@@ -52,6 +52,7 @@ Possible debug options are::
A Toggle failslab filter mark for the cache
O Switch debugging off for caches that would have
caused higher minimum slab orders
+ W Toggle WARN_ON() on slab errors
- Switch all debugging off (useful if the kernel is
configured with CONFIG_SLUB_DEBUG_ON)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 11b45f7ae405..1fd9911890c6 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -109,6 +109,9 @@
#define SLAB_KASAN 0
#endif
+/* WARN_ON slab error */
+#define SLAB_WARN_ON_ERROR ((slab_flags_t __force)0x10000000U)
+
/* The following flags affect the page allocator grouping pages by mobility */
/* Objects are reclaimable */
#define SLAB_RECLAIM_ACCOUNT ((slab_flags_t __force)0x00020000U)
diff --git a/mm/slub.c b/mm/slub.c
index 1e3d0ec4e200..60f93e0657fb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -684,7 +684,10 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
print_section(KERN_ERR, "Padding ", p + off,
size_from_object(s) - off);
- dump_stack();
+ if (unlikely(s->flags & SLAB_WARN_ON_ERROR))
+ WARN_ON(1);
+ else
+ dump_stack();
}
void object_err(struct kmem_cache *s, struct page *page,
@@ -705,7 +708,11 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
va_end(args);
slab_bug(s, "%s", buf);
print_page_info(page);
- dump_stack();
+
+ if (unlikely(s->flags & SLAB_WARN_ON_ERROR))
+ WARN_ON(1);
+ else
+ dump_stack();
}
static void init_object(struct kmem_cache *s, void *object, u8 val)
@@ -1254,6 +1261,9 @@ static int __init setup_slub_debug(char *str)
case 'a':
slub_debug |= SLAB_FAILSLAB;
break;
+ case 'w':
+ slub_debug |= SLAB_WARN_ON_ERROR;
+ break;
case 'o':
/*
* Avoid enabling debugging on caches if its minimum
@@ -5220,6 +5230,25 @@ static ssize_t store_user_store(struct kmem_cache *s,
}
SLAB_ATTR(store_user);
+static ssize_t warn_on_error_show(struct kmem_cache *s, char *buf)
+{
+ return sprintf(buf, "%d\n", !!(s->flags & SLAB_WARN_ON_ERROR));
+}
+
+static ssize_t warn_on_error_store(struct kmem_cache *s,
+ const char *buf, size_t length)
+{
+ if (any_slab_objects(s))
+ return -EBUSY;
+
+ s->flags &= ~SLAB_WARN_ON_ERROR;
+ if (buf[0] == '1')
+ s->flags |= SLAB_WARN_ON_ERROR;
+
+ return length;
+}
+SLAB_ATTR(warn_on_error);
+
static ssize_t validate_show(struct kmem_cache *s, char *buf)
{
return 0;
@@ -5428,6 +5457,7 @@ static struct attribute *slab_attrs[] = {
&validate_attr.attr,
&alloc_calls_attr.attr,
&free_calls_attr.attr,
+ &warn_on_error_attr.attr,
#endif
#ifdef CONFIG_ZONE_DMA
&cache_dma_attr.attr,
--
2.18.0
