[Qemu-devel] [PATCH] block: get_block_status: use "else" when testing the opposite condition

[Qemu-devel] [PATCH] block: get_block_status: use "else" when testing the opposite condition

[Paolo Bonzini]

A bit of Boolean algebra (and common sense) tells us that the
second "if" here is looking for blocks that are not allocated.
This is the opposite of the "if" that sets BDRV_BLOCK_ALLOCATED,
and thus it can use an "else".

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/io.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/block/io.c b/block/io.c
index 1ce62c4..494e3b3 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1456,9 +1456,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
 
     if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
         ret |= BDRV_BLOCK_ALLOCATED;
-    }
-
-    if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) {
+    } else {
         if (bdrv_unallocated_blocks_are_zero(bs)) {
             ret |= BDRV_BLOCK_ZERO;
         } else if (bs->backing_hd) {
-- 
2.4.0

Re: [Qemu-devel] [PATCH] block: get_block_status: use "else" when testing the opposite condition

[Eric Blake]

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On 05/14/2015 04:35 AM, Paolo Bonzini wrote:
> A bit of Boolean algebra (and common sense) tells us that the
> second "if" here is looking for blocks that are not allocated.
> This is the opposite of the "if" that sets BDRV_BLOCK_ALLOCATED,
> and thus it can use an "else".
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/io.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

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


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Re: [Qemu-devel] [PATCH] block: get_block_status: use "else" when testing the opposite condition

[Fam Zheng]

On Thu, 05/14 12:35, Paolo Bonzini wrote:
> A bit of Boolean algebra (and common sense) tells us that the
> second "if" here is looking for blocks that are not allocated.
> This is the opposite of the "if" that sets BDRV_BLOCK_ALLOCATED,
> and thus it can use an "else".
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/io.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 1ce62c4..494e3b3 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1456,9 +1456,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
>  
>      if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
>          ret |= BDRV_BLOCK_ALLOCATED;
> -    }
> -
> -    if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) {
> +    } else {
>          if (bdrv_unallocated_blocks_are_zero(bs)) {
>              ret |= BDRV_BLOCK_ZERO;
>          } else if (bs->backing_hd) {
> -- 
> 2.4.0
> 

Reviewed-by: Fam Zheng <famz@redhat.com>

Re: [Qemu-devel] [PATCH] block: get_block_status: use "else" when testing the opposite condition

[Stefan Hajnoczi]

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On Thu, May 14, 2015 at 12:35:02PM +0200, Paolo Bonzini wrote:
> A bit of Boolean algebra (and common sense) tells us that the
> second "if" here is looking for blocks that are not allocated.
> This is the opposite of the "if" that sets BDRV_BLOCK_ALLOCATED,
> and thus it can use an "else".
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/io.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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