SLUB: Do not allocate object bit array on stack

The objects per slab increase with the current patches in mm since we allow up
to order 3 allocs by default.  More patches in mm actually allow to use 2M or
higher sized slabs.  For slab validation we need per object bitmaps in order
to check a slab.  We end up with up to 64k objects per slab resulting in a
potential requirement of 8K stack space.  That does not look good.

Allocate the bit arrays via kmalloc.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 14 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 510ee9a2cdb2..f976d2866e73 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2764,11 +2764,11 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
 }
 
 #if defined(CONFIG_SYSFS) && defined(CONFIG_SLUB_DEBUG)
-static int validate_slab(struct kmem_cache *s, struct page *page)
+static int validate_slab(struct kmem_cache *s, struct page *page,
+                                                unsigned long *map)
 {
         void *p;
         void *addr = page_address(page);
-        DECLARE_BITMAP(map, s->objects);
 
         if (!check_slab(s, page) ||
                         !on_freelist(s, page, NULL))
@@ -2790,10 +2790,11 @@ static int validate_slab(struct kmem_cache *s, struct page *page)
         return 1;
 }
 
-static void validate_slab_slab(struct kmem_cache *s, struct page *page)
+static void validate_slab_slab(struct kmem_cache *s, struct page *page,
+                                                unsigned long *map)
 {
         if (slab_trylock(page)) {
-                validate_slab(s, page);
+                validate_slab(s, page, map);
                 slab_unlock(page);
         } else
                 printk(KERN_INFO "SLUB %s: Skipped busy slab 0x%p\n",
@@ -2810,7 +2811,8 @@ static void validate_slab_slab(struct kmem_cache *s, struct page *page)
         }
 }
 
-static int validate_slab_node(struct kmem_cache *s, struct kmem_cache_node *n)
+static int validate_slab_node(struct kmem_cache *s,
+                struct kmem_cache_node *n, unsigned long *map)
 {
         unsigned long count = 0;
         struct page *page;
@@ -2819,7 +2821,7 @@ static int validate_slab_node(struct kmem_cache *s, struct kmem_cache_node *n)
         spin_lock_irqsave(&n->list_lock, flags);
 
         list_for_each_entry(page, &n->partial, lru) {
-                validate_slab_slab(s, page);
+                validate_slab_slab(s, page, map);
                 count++;
         }
         if (count != n->nr_partial)
@@ -2830,7 +2832,7 @@ static int validate_slab_node(struct kmem_cache *s, struct kmem_cache_node *n)
                 goto out;
 
         list_for_each_entry(page, &n->full, lru) {
-                validate_slab_slab(s, page);
+                validate_slab_slab(s, page, map);
                 count++;
         }
         if (count != atomic_long_read(&n->nr_slabs))
@@ -2843,17 +2845,23 @@ out:
         return count;
 }
 
-static unsigned long validate_slab_cache(struct kmem_cache *s)
+static long validate_slab_cache(struct kmem_cache *s)
 {
         int node;
         unsigned long count = 0;
+        unsigned long *map = kmalloc(BITS_TO_LONGS(s->objects) *
+                                sizeof(unsigned long), GFP_KERNEL);
+
+        if (!map)
+                return -ENOMEM;
 
         flush_all(s);
         for_each_online_node(node) {
                 struct kmem_cache_node *n = get_node(s, node);
 
-                count += validate_slab_node(s, n);
+                count += validate_slab_node(s, n, map);
         }
+        kfree(map);
         return count;
 }
 
@@ -3467,11 +3475,14 @@ static ssize_t validate_show(struct kmem_cache *s, char *buf)
 static ssize_t validate_store(struct kmem_cache *s,
                         const char *buf, size_t length)
 {
-        if (buf[0] == '1')
-                validate_slab_cache(s);
-        else
-                return -EINVAL;
-        return length;
+        int ret = -EINVAL;
+
+        if (buf[0] == '1') {
+                ret = validate_slab_cache(s);
+                if (ret >= 0)
+                        ret = length;
+        }
+        return ret;
 }
 SLAB_ATTR(validate);