Re: [Qemu-devel] [PATCH v3 3/5] raw-posix: DPRINTF instead of DEBUG_BLOCK_PRINT

[Eric Blake <eblake@redhat.com>]

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On 05/14/2015 05:01 AM, Dimitris Aragiorgis wrote:
> Building the QEMU tools fails if we #define DEBUG_BLOCK inside
> block/raw-posix.c. Here instead of adding qemu-log.o in block-obj-y
> so that DEBUG_BLOCK_PRINT can be used, we substitute the latter with
> a simple DPRINTF() (that does not cause bit-rot).
> 
> Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
> ---
>  block/raw-posix.c |   17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 

> +#define DPRINTF(fmt, ...) \
> +do { \
> +    if (DEBUG_BLOCK_PRINT) \
> +        printf(fmt, ## __VA_ARGS__); \
> +} while (0)

Still missing {} for the if statement.

[It might be nice to update scripts/checkpatch.pl to catch correct {}
inside macros, but that's a project for a different day.]

> @@ -1023,7 +1028,7 @@ static int xfs_write_zeroes(BDRVRawState *s, int64_t offset, uint64_t bytes)
>      fl.l_len = bytes;
>  
>      if (xfsctl(NULL, s->fd, XFS_IOC_ZERO_RANGE, &fl) < 0) {
> -        DEBUG_BLOCK_PRINT("cannot write zero range (%s)\n", strerror(errno));
> +        DPRINTF("cannot write zero range (%s)\n", strerror(errno));
>          return -errno;
>      }

Pre-existing bug - strerror() and/or DPRINTF() can clobber errno, so
your return value may be destroyed.  You'll have to save errno into a
temporary variable prior to DPRINTF, and return that value.

>  
> @@ -1040,7 +1045,7 @@ static int xfs_discard(BDRVRawState *s, int64_t offset, uint64_t bytes)
>      fl.l_len = bytes;
>  
>      if (xfsctl(NULL, s->fd, XFS_IOC_UNRESVSP64, &fl) < 0) {
> -        DEBUG_BLOCK_PRINT("cannot punch hole (%s)\n", strerror(errno));
> +        DPRINTF("cannot punch hole (%s)\n", strerror(errno));
>          return -errno;

Here too.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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