Re: [Qemu-devel] [Qemu-block] [PATCH] block: Use QEMU_IS_ALIGNED instead of reinventing it

[John Snow <jsnow@redhat.com>]

On 8/17/19 1:53 PM, Nir Soffer wrote:
> Replace instances of:
> 
>     (n & (BDRV_SECTOR_SIZE - 1)) == 0)
> 
> With:
> 
>     QEMU_IS_ALIGNED(n, BDRV_SECTOR_SIZE)
> 

Do you have a magical incantation you used to find these?

> Which reveals the intent of the code better, and makes it easier to
> locate the code checking alignment.
> 
> QEMU_IS_ALIGNED is implemented using %, which may be less efficient but
> it is used only in assert() except one instance, so it should not
> matter.
> 

There is virtually no way these aren't optimized by the compiler.

> Signed-off-by: Nir Soffer <nsoffer@redhat.com>

Therefore:

Reviewed-by: John Snow <jsnow@redhat.com>

> ---
>  block/bochs.c | 4 ++--
>  block/cloop.c | 4 ++--
>  block/dmg.c   | 4 ++--
>  block/io.c    | 8 ++++----
>  block/qcow2.c | 4 ++--
>  block/vvfat.c | 8 ++++----
>  qemu-img.c    | 2 +-
>  7 files changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/block/bochs.c b/block/bochs.c
> index 962f18592d..32bb83b268 100644
> --- a/block/bochs.c
> +++ b/block/bochs.c
> @@ -248,8 +248,8 @@ bochs_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      QEMUIOVector local_qiov;
>      int ret;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>  
>      qemu_iovec_init(&local_qiov, qiov->niov);
>      qemu_co_mutex_lock(&s->lock);
> diff --git a/block/cloop.c b/block/cloop.c
> index 384c9735bb..4de94876d4 100644
> --- a/block/cloop.c
> +++ b/block/cloop.c
> @@ -253,8 +253,8 @@ cloop_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      int nb_sectors = bytes >> BDRV_SECTOR_BITS;
>      int ret, i;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>  
>      qemu_co_mutex_lock(&s->lock);
>  
> diff --git a/block/dmg.c b/block/dmg.c
> index 45f6b28f17..4a045f2b3e 100644
> --- a/block/dmg.c
> +++ b/block/dmg.c
> @@ -697,8 +697,8 @@ dmg_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      int nb_sectors = bytes >> BDRV_SECTOR_BITS;
>      int ret, i;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>  
>      qemu_co_mutex_lock(&s->lock);
>  
> diff --git a/block/io.c b/block/io.c
> index 56bbf195bb..7508703ecd 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1080,8 +1080,8 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
>      sector_num = offset >> BDRV_SECTOR_BITS;
>      nb_sectors = bytes >> BDRV_SECTOR_BITS;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>      assert(bytes <= BDRV_REQUEST_MAX_BYTES);
>      assert(drv->bdrv_co_readv);
>  
> @@ -1133,8 +1133,8 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
>      sector_num = offset >> BDRV_SECTOR_BITS;
>      nb_sectors = bytes >> BDRV_SECTOR_BITS;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>      assert(bytes <= BDRV_REQUEST_MAX_BYTES);
>  
>      assert(drv->bdrv_co_writev);
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 59cff1d4cb..41cab70e1d 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2072,8 +2072,8 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
>              }
>              if (bs->encrypted) {
>                  assert(s->crypto);
> -                assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -                assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +                assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +                assert(QEMU_IS_ALIGNED(cur_bytes, BDRV_SECTOR_SIZE));
>                  if (qcow2_co_decrypt(bs, cluster_offset, offset,
>                                       cluster_data, cur_bytes) < 0) {
>                      ret = -EIO;
> diff --git a/block/vvfat.c b/block/vvfat.c
> index f6c28805dd..019b8f1341 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1547,8 +1547,8 @@ vvfat_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      int nb_sectors = bytes >> BDRV_SECTOR_BITS;
>      void *buf;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>  
>      buf = g_try_malloc(bytes);
>      if (bytes && buf == NULL) {
> @@ -3082,8 +3082,8 @@ vvfat_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
>      int nb_sectors = bytes >> BDRV_SECTOR_BITS;
>      void *buf;
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
>  
>      buf = g_try_malloc(bytes);
>      if (bytes && buf == NULL) {
> diff --git a/qemu-img.c b/qemu-img.c
> index c920e3564c..ca3af0c549 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -2138,7 +2138,7 @@ static int img_convert(int argc, char **argv)
>              int64_t sval;
>  
>              sval = cvtnum(optarg);
> -            if (sval < 0 || sval & (BDRV_SECTOR_SIZE - 1) ||
> +            if (sval < 0 || !QEMU_IS_ALIGNED(sval, BDRV_SECTOR_SIZE) ||
>                  sval / BDRV_SECTOR_SIZE > MAX_BUF_SECTORS) {
>                  error_report("Invalid buffer size for sparse output specified. "
>                      "Valid sizes are multiples of %llu up to %llu. Select "
>