slub: Store max number of objects in the page struct.
Split the inuse field up to be able to store the number of objects in this
page in the page struct as well. Necessary if we want to have pages of
various orders for a slab. Also avoids touching struct kmem_cache cachelines in
__slab_alloc().
Update diagnostic code to check the number of objects and make sure that
the number of objects always stays within the bounds of a 16 bit unsigned
integer.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
diff --git a/mm/slub.c b/mm/slub.c
index 64c2b2b..6641025 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -301,7 +301,7 @@
return 1;
base = page_address(page);
- if (object < base || object >= base + s->objects * s->size ||
+ if (object < base || object >= base + page->objects * s->size ||
(object - base) % s->size) {
return 0;
}
@@ -451,8 +451,8 @@
static void print_page_info(struct page *page)
{
- printk(KERN_ERR "INFO: Slab 0x%p used=%u fp=0x%p flags=0x%04lx\n",
- page, page->inuse, page->freelist, page->flags);
+ printk(KERN_ERR "INFO: Slab 0x%p objects=%u used=%u fp=0x%p flags=0x%04lx\n",
+ page, page->objects, page->inuse, page->freelist, page->flags);
}
@@ -652,6 +652,7 @@
p + off, POISON_INUSE, s->size - off);
}
+/* Check the pad bytes at the end of a slab page */
static int slab_pad_check(struct kmem_cache *s, struct page *page)
{
u8 *start;
@@ -664,20 +665,20 @@
return 1;
start = page_address(page);
- end = start + (PAGE_SIZE << s->order);
- length = s->objects * s->size;
- remainder = end - (start + length);
+ length = (PAGE_SIZE << s->order);
+ end = start + length;
+ remainder = length % s->size;
if (!remainder)
return 1;
- fault = check_bytes(start + length, POISON_INUSE, remainder);
+ fault = check_bytes(end - remainder, POISON_INUSE, remainder);
if (!fault)
return 1;
while (end > fault && end[-1] == POISON_INUSE)
end--;
slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
- print_section("Padding", start, length);
+ print_section("Padding", end - remainder, remainder);
restore_bytes(s, "slab padding", POISON_INUSE, start, end);
return 0;
@@ -739,15 +740,24 @@
static int check_slab(struct kmem_cache *s, struct page *page)
{
+ int maxobj;
+
VM_BUG_ON(!irqs_disabled());
if (!PageSlab(page)) {
slab_err(s, page, "Not a valid slab page");
return 0;
}
- if (page->inuse > s->objects) {
+
+ maxobj = (PAGE_SIZE << compound_order(page)) / s->size;
+ if (page->objects > maxobj) {
+ slab_err(s, page, "objects %u > max %u",
+ s->name, page->objects, maxobj);
+ return 0;
+ }
+ if (page->inuse > page->objects) {
slab_err(s, page, "inuse %u > max %u",
- s->name, page->inuse, s->objects);
+ s->name, page->inuse, page->objects);
return 0;
}
/* Slab_pad_check fixes things up after itself */
@@ -765,7 +775,7 @@
void *fp = page->freelist;
void *object = NULL;
- while (fp && nr <= s->objects) {
+ while (fp && nr <= page->objects) {
if (fp == search)
return 1;
if (!check_valid_pointer(s, page, fp)) {
@@ -777,7 +787,7 @@
} else {
slab_err(s, page, "Freepointer corrupt");
page->freelist = NULL;
- page->inuse = s->objects;
+ page->inuse = page->objects;
slab_fix(s, "Freelist cleared");
return 0;
}
@@ -788,10 +798,10 @@
nr++;
}
- if (page->inuse != s->objects - nr) {
+ if (page->inuse != page->objects - nr) {
slab_err(s, page, "Wrong object count. Counter is %d but "
- "counted were %d", page->inuse, s->objects - nr);
- page->inuse = s->objects - nr;
+ "counted were %d", page->inuse, page->objects - nr);
+ page->inuse = page->objects - nr;
slab_fix(s, "Object count adjusted.");
}
return search == NULL;
@@ -910,7 +920,7 @@
* as used avoids touching the remaining objects.
*/
slab_fix(s, "Marking all objects used");
- page->inuse = s->objects;
+ page->inuse = page->objects;
page->freelist = NULL;
}
return 0;
@@ -1081,6 +1091,7 @@
if (!page)
return NULL;
+ page->objects = s->objects;
mod_zone_page_state(page_zone(page),
(s->flags & SLAB_RECLAIM_ACCOUNT) ?
NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
@@ -1519,7 +1530,7 @@
goto debug;
c->freelist = object[c->offset];
- c->page->inuse = s->objects;
+ c->page->inuse = c->page->objects;
c->page->freelist = NULL;
c->node = page_to_nid(c->page);
unlock_out:
@@ -1818,6 +1829,9 @@
int rem;
int min_order = slub_min_order;
+ if ((PAGE_SIZE << min_order) / size > 65535)
+ return get_order(size * 65535) - 1;
+
for (order = max(min_order,
fls(min_objects * size - 1) - PAGE_SHIFT);
order <= max_order; order++) {
@@ -3251,7 +3265,7 @@
return 0;
/* Now we know that a valid freelist exists */
- bitmap_zero(map, s->objects);
+ bitmap_zero(map, page->objects);
for_each_free_object(p, s, page->freelist) {
set_bit(slab_index(p, s, addr), map);
@@ -3528,10 +3542,10 @@
struct page *page, enum track_item alloc)
{
void *addr = page_address(page);
- DECLARE_BITMAP(map, s->objects);
+ DECLARE_BITMAP(map, page->objects);
void *p;
- bitmap_zero(map, s->objects);
+ bitmap_zero(map, page->objects);
for_each_free_object(p, s, page->freelist)
set_bit(slab_index(p, s, addr), map);