[PATCH] valid_swaphandles() fix
akpm draws my attention to the fact that sysctl(VM_PAGE_CLUSTER) might
conceivably change page_cluster to 0 while valid_swaphandles() is in the
middle of using it, leading to an embarrassingly long loop: take a local
snapshot of page_cluster and work with that.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f1f5ec7..a15def6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1723,13 +1723,14 @@
*/
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
- int ret = 0, i = 1 << page_cluster;
+ int our_page_cluster = page_cluster;
+ int ret = 0, i = 1 << our_page_cluster;
unsigned long toff;
struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
- if (!page_cluster) /* no readahead */
+ if (!our_page_cluster) /* no readahead */
return 0;
- toff = (swp_offset(entry) >> page_cluster) << page_cluster;
+ toff = (swp_offset(entry) >> our_page_cluster) << our_page_cluster;
if (!toff) /* first page is swap header */
toff++, i--;
*offset = toff;