[PATCH] rbd: silence GCC warnings

[Paul Bolle <pebolle@tiscali.nl>]

Building rbd.o triggers two GCC warnings:
    drivers/block/rbd.c: In function ‘rbd_img_request_fill’:
    drivers/block/rbd.c:1272:22: warning: ‘bio_list’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    drivers/block/rbd.c:2170:14: note: ‘bio_list’ was declared here
    drivers/block/rbd.c:2231:10: warning: ‘pages’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Apparently GCC has trouble determining that "bio_list" is unused if "type"
is "OBJ_REQUEST_PAGES" and, conversely, that "pages" will be unused if
"type" is "OBJ_REQUEST_BIO". Add harmless initializations to NULL to
help GCC.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
---
0) Compile tested only.

1) These warnings were introduced in v3.10-rc1, apparently through
commit f1a4739f33 ("rbd: support page array image requests"). 

2) Note that
    rbd_assert(type == OBJ_REQUEST_PAGES);

seems redundant. I see no way that this assertion could ever be false. 

 drivers/block/rbd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 3063452..b8a58178 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2185,9 +2185,11 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 	if (type == OBJ_REQUEST_BIO) {
 		bio_list = data_desc;
 		rbd_assert(img_offset == bio_list->bi_sector << SECTOR_SHIFT);
+		pages = NULL;
 	} else {
 		rbd_assert(type == OBJ_REQUEST_PAGES);
 		pages = data_desc;
+		bio_list = NULL;
 	}
 
 	while (resid) {
-- 
1.8.1.4