[PATCH] tmpfs: fix mounts when size is less than the page size

[Michael Marineau <mike@marineau.org>]

When tmpfs is mounted with a size less than one page the number of blocks
is set to 0 which makes the tmpfs mount unlimited. This can lead to a quick
and surprising death is someone typos a tmpfs mount command and writes to much.

tmpfs can still be mounted as unlimited if size or nr_blocks is exactly 0.

Signed-off-by: Michael Marineau <mike@marineau.org>
---
 mm/shmem.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 253d205..66b07f2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2138,6 +2138,8 @@ static int shmem_parse_options(char *options, int *mode, uid_t *uid,
 			if (*rest)
 				goto bad_val;
 			*blocks = size >> PAGE_CACHE_SHIFT;
+			if (size && blocks == 0)
+				blocks = 1;
 		} else if (!strcmp(this_char,"nr_blocks")) {
 			*blocks = memparse(value,&rest);
 			if (*rest)
-- 
1.5.1.6