[PATCH v2] swap: warn when a swap area overflows the maximum size

Raymond Jennings
2013-07-07T19:13:46Z

Turned the comparison around for clarity of "bigger than"

No semantic changes, if it still compiles it should do the same thing so
I've omitted the testing this time. Will be happy to retest if required
but I'm on an atom 330 and kernel rebuilds are a nightmare.

----

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.

Signed-off-by: Raymond Jennings <shentino@gmail.com>
Acked-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>

----

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 36af6ee..5a4ce53 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct
swap_info_struct *p,
*/
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));