[PATCH 2/2] Btrfs: fix off-by-one error of the reserved size of btrfs_allocate()

[PATCH 2/2] Btrfs: fix off-by-one error of the reserved size of btrfs_allocate()

[Miao Xie]

alloc_end is not the real end of the current extent, it is the start of the
next adjoining extent. So we needn't +1 when calculating the size the space
that is about to be reserved.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 641bbaa..bd5afcc 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2085,7 +2085,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 	 * Make sure we have enough space before we do the
 	 * allocation.
 	 */
-	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start + 1);
+	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start);
 	if (ret)
 		return ret;
 
@@ -2192,7 +2192,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 out:
 	mutex_unlock(&inode->i_mutex);
 	/* Let go of our reservation. */
-	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start + 1);
+	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
 	return ret;
 }
 
-- 
1.7.11.7

Re: [PATCH 2/2] Btrfs: fix off-by-one error of the reserved size of btrfs_allocate()

[Liu Bo]

On Wed, Nov 28, 2012 at 06:28:54PM +0800, Miao Xie wrote:
> alloc_end is not the real end of the current extent, it is the start of the
> next adjoining extent. So we needn't +1 when calculating the size the space
> that is about to be reserved.
> 

Good catch.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

thanks,
liubo

> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
> ---
>  fs/btrfs/file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 641bbaa..bd5afcc 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -2085,7 +2085,7 @@ static long btrfs_fallocate(struct file *file, int mode,
>  	 * Make sure we have enough space before we do the
>  	 * allocation.
>  	 */
> -	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start + 1);
> +	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start);
>  	if (ret)
>  		return ret;
>  
> @@ -2192,7 +2192,7 @@ static long btrfs_fallocate(struct file *file, int mode,
>  out:
>  	mutex_unlock(&inode->i_mutex);
>  	/* Let go of our reservation. */
> -	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start + 1);
> +	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
>  	return ret;
>  }
>  
> -- 
> 1.7.11.7
> --
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