Re: [Qemu-devel] [Qemu-block] [PATCH for-2.9?] block/file-posix.c: Fix unused variable warning on OpenBSD

[Philippe Mathieu-Daudé]

On 03/22/2017 01:23 PM, Philippe Mathieu-Daudé wrote:

On 03/22/2017 10:58 AM, Jeff Cody wrote:

On Mon, Mar 20, 2017 at 06:33:04PM +0000, Peter Maydell wrote:

On OpenBSD none of the ioctls probe_logical_blocksize() tries
exist, so the variable sector_size is unused. Refactor the
code to avoid this (and reduce the duplicated code).

Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
The alternative would be to move the variable so it was
local to a code block inside each #ifdef, but this seemed
a bit nicer anyway.

Tentatively tagged 'for-2.9' just because this is the only
warning in the OpenBSD build, but I don't insist on it.

I've opted to retain the existing behaviour of "try every
ioctl available and use the last one that works" rather
than "stop as soon as something worked".

---
 block/file-posix.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 53febd3..b980d23 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -219,28 +219,28 @@ static int probe_logical_blocksize(int fd,
unsigned int *sector_size_p)
 {
     unsigned int sector_size;
     bool success = false;
+    int i;

     errno = ENOTSUP;
-
-    /* Try a few ioctls to get the right size */
+    unsigned long ioctl_list[] = {

this can be `const` but not a bit win.

I mean `static const`, sorry.

 #ifdef BLKSSZGET
-    if (ioctl(fd, BLKSSZGET, &sector_size) >= 0) {
-        *sector_size_p = sector_size;
-        success = true;
-    }
+        BLKSSZGET,
 #endif
 #ifdef DKIOCGETBLOCKSIZE
-    if (ioctl(fd, DKIOCGETBLOCKSIZE, &sector_size) >= 0) {
-        *sector_size_p = sector_size;
-        success = true;
-    }
+        DKIOCGETBLOCKSIZE,
 #endif
 #ifdef DIOCGSECTORSIZE
-    if (ioctl(fd, DIOCGSECTORSIZE, &sector_size) >= 0) {
-        *sector_size_p = sector_size;
-        success = true;
-    }
+        DIOCGSECTORSIZE,
 #endif
+    };
+
+    /* Try a few ioctls to get the right size */
+    for (i = 0; i < ARRAY_SIZE(ioctl_list); i++) {
+        if (ioctl(fd, ioctl_list[i], &sector_size) >= 0) {
+            *sector_size_p = sector_size;
+            success = true;
+        }
+    }

     return success ? 0 : -errno;
 }
--
2.7.4

Reviewed-by: Jeff Cody <jc...@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>