I checked the mmotm queue and it seems that my mid-air corrections got
the patch mangled when it was saved to your mail queue, and in addition
to a missing correction of a typo in my testing log, Rik van Riel's
Reviewed-By tag vanished
http://www.ozlabs.org/~akpm/mmotm/broken-out/swap-warn-when-a-swap-area-overflows-the-maximum-size.patch
If you could fix my test transcript and properly credit Rik for
reviewing my patch before you ship it to linus I'd appreciate it.
The correctly formatted patch and description with corrections and tags
follows:
----
From: Raymond Jennings <[email protected]>
Subject: swap: warn when a swap area overflows the maximum size
It is possible to swapon a swap area that is too big for the pte width
to handle.
Presently this failure happens silently.
Instead, emit a diagnostic to warn the user.
Testing results, root prompt commands and kernel log messages:
# lvresize /dev/system/swap --size 16G
# mkswap /dev/system/swap
# swapon /dev/system/swap
Jul 7 04:27:22 warfang kernel: Adding 16777212k swap
on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k
# lvresize /dev/system/swap --size 64G
# mkswap /dev/system/swap
# swapon /dev/system/swap
Jul 7 04:27:22 warfang kernel: Truncating oversized swap area, only
using 33554432k out of 67108860k
Jul 7 04:27:22 warfang kernel: Adding 33554428k swap
on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k
Signed-off-by: Raymond Jennings <[email protected]>
Acked-by: Valdis Kletnieks <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
mm/swapfile.c | 6 ++++++
1 file changed, 6 insertions(+)
diff -puN
mm/swapfile.c~swap-warn-when-a-swap-area-overflows-the-maximum-size
mm/swapfile.c
---
a/mm/swapfile.c~swap-warn-when-a-swap-area-overflows-the-maximum-size
+++ a/mm/swapfile.c
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(st
*/
maxpages = swp_offset(pte_to_swp_entry(
swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+ if (swap_header->info.last_page > maxpages) {
+ printk(KERN_WARNING
+ "Truncating oversized swap area, only using %luk out of %luk\n",
+ maxpages << (PAGE_SHIFT - 10),
+ swap_header->info.last_page << (PAGE_SHIFT - 10));
+ }
if (maxpages > swap_header->info.last_page) {
maxpages = swap_header->info.last_page + 1;
/* p->max is an unsigned int: don't overflow it */