[5/5] raw-posix: add discard support

Add support to discard blocks in a raw image residing on an XFS filesystem
by calling the XFS_IOC_UNRESVSP64 ioctl to punch holes.  Support for other
hole punching mechanisms can be added when they become available.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Am 01.12.2010 16:35, schrieb Christoph Hellwig:
> Add support to discard blocks in a raw image residing on an XFS filesystem
> by calling the XFS_IOC_UNRESVSP64 ioctl to punch holes.  Support for other
> hole punching mechanisms can be added when they become available.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Index: qemu/block/raw-posix.c
> ===================================================================
> --- qemu.orig/block/raw-posix.c	2010-11-25 12:51:18.474004263 +0100
> +++ qemu/block/raw-posix.c	2010-11-25 13:00:42.220003844 +0100
> @@ -69,6 +69,10 @@
>  #include <sys/diskslice.h>
>  #endif
>  
> +#ifdef CONFIG_XFS
> +#include <xfs/xfs.h>
> +#endif
> +
>  //#define DEBUG_FLOPPY
>  
>  //#define DEBUG_BLOCK
> @@ -120,6 +124,9 @@ typedef struct BDRVRawState {
>  #endif
>      uint8_t *aligned_buf;
>      unsigned aligned_buf_size;
> +#ifdef CONFIG_XFS
> +    int is_xfs : 1;
> +#endif

Why not bool?

>  } BDRVRawState;
>  
>  static int fd_open(BlockDriverState *bs);
> @@ -196,6 +203,12 @@ static int raw_open_common(BlockDriverSt
>  #endif
>      }
>  
> +#ifdef CONFIG_XFS
> +    if (platform_test_xfs_fd(s->fd)) {
> +        s->is_xfs = 1;
> +    }
> +#endif
> +
>      return 0;
>  
>  out_free_buf:
> @@ -740,6 +753,36 @@ static int raw_flush(BlockDriverState *b
>      return qemu_fdatasync(s->fd);
>  }
>  
> +#ifdef CONFIG_XFS
> +static int xfs_discard(BDRVRawState *s, int64_t sector_num, int nb_sectors)
> +{
> +    struct xfs_flock64 fl;
> +
> +    memset(&fl, 0, sizeof(fl));
> +    fl.l_whence = SEEK_SET;
> +    fl.l_start = sector_num << 9;
> +    fl.l_len = (int64_t)nb_sectors << 9;
> +
> +    if (xfsctl(NULL, s->fd, XFS_IOC_UNRESVSP64, &fl) < 0) {
> +        printf("cannot punch hole (%s)\n", strerror(errno));
> +        return -errno;
> +    }
> +
> +    return 0;
> +}
> +#endif
> +
> +static int raw_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
> +{
> +    BDRVRawState *s = bs->opaque;
> +
> +#ifdef CONFIG_XFS
> +    if (s->is_xfs)
> +        return xfs_discard(s, sector_num, nb_sectors);

Braces

> +#endif
> +
> +    return 0;
> +}

This doesn't compile without XFS:

cc1: warnings being treated as errors
block/raw-posix.c: In function 'raw_discard':
block/raw-posix.c:777: error: unused variable 's'

>  
>  static QEMUOptionParameter raw_create_options[] = {
>      {
> @@ -761,6 +804,7 @@ static BlockDriver bdrv_file = {
>      .bdrv_close = raw_close,
>      .bdrv_create = raw_create,
>      .bdrv_flush = raw_flush,
> +    .bdrv_discard = raw_discard,
>  
>      .bdrv_aio_readv = raw_aio_readv,
>      .bdrv_aio_writev = raw_aio_writev,
> Index: qemu/configure
> ===================================================================
> --- qemu.orig/configure	2010-11-25 12:51:18.484004891 +0100
> +++ qemu/configure	2010-11-25 13:00:42.222004263 +0100
> @@ -288,6 +288,7 @@ xen=""
>  linux_aio=""
>  attr=""
>  vhost_net=""
> +xfs=""
>  
>  gprof="no"
>  debug_tcg="no"
> @@ -1393,6 +1394,27 @@ EOF
>  fi
>  
>  ##########################################
> +# xfsctl() probe, used for raw-posix
> +if test "$xfs" != "no" ; then
> +  cat > $TMPC << EOF
> +#include <xfs/xfs.h>
> +int main(void)
> +{
> +    xfsctl(NULL, 0, 0, NULL);
> +    return 0;
> +}
> +EOF
> +  if compile_prog "" "" ; then
> +    xfs="yes"
> +  else
> +    if test "$xfs" = "yes" ; then
> +      feature_not_found "uuid"

s/uuid/xfs/

Kevin