[66/75] block: avoid using uninitialized value in from queue_var_store

[Ben Hutchings <ben@decadent.org.uk>]

3.2.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@arndb.de>

commit c678ef5286ddb5cf70384ad5af286b0afc9b73e1 upstream.

As found by gcc-4.8, the QUEUE_SYSFS_BIT_FNS macro creates functions
that use a value generated by queue_var_store independent of whether
that value was set or not.

block/blk-sysfs.c: In function 'queue_store_nonrot':
block/blk-sysfs.c:244:385: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]

Unlike most other such warnings, this one is not a false positive,
writing any non-number string into the sysfs files indeed has
an undefined result, rather than returning an error.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 block/blk-sysfs.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -200,6 +200,8 @@ queue_store_##name(struct request_queue
 	unsigned long val;						\
 	ssize_t ret;							\
 	ret = queue_var_store(&val, page, count);			\
+	if (ret < 0)							\
+		 return ret;						\
 	if (neg)							\
 		val = !val;						\
 									\