2013-06-17 10:12:47

by Paul Bolle

[permalink] [raw]
Subject: [PATCH] rbd: silence GCC warnings

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 <[email protected]>
---
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


2013-06-18 15:10:49

by Sage Weil

[permalink] [raw]
Subject: Re: [PATCH] rbd: silence GCC warnings

This was already fixed up in teh testing branch; thanks!

On Mon, 17 Jun 2013, Paul Bolle wrote:

> 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 <[email protected]>
> ---
> 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
>
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