Re: [PATCH] Btrfs: Improve FL_KEEP_SIZE handling in fallocate.

[Liu Bo <bo.li.liu@oracle.com>]

On Mon, Apr 06, 2015 at 10:09:15PM -0700, Davide Italiano wrote:
> - We call inode_size_ok() only if FL_KEEP_SIZE isn't specified.
> - As an optimisation we can skip the call if (off + len)
>   isn't greater than the current size of the file. This operation
>   is called under the lock so the less work we do, the better.
> - If we call inode_size_ok() pass to it the correct value rather
>   than a more conservative estimation.

Looks good.

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

> 
> Signed-off-by: Davide Italiano <dccitaliano@gmail.com>
> ---
>  fs/btrfs/file.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 30982bb..f649bfc 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -2586,9 +2586,13 @@ static long btrfs_fallocate(struct file *file, int mode,
>  	}
>  
>  	mutex_lock(&inode->i_mutex);
> -	ret = inode_newsize_ok(inode, alloc_end);
> -	if (ret)
> -		goto out;
> +
> +	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
> +	    offset + len > inode->i_size) {
> +		ret = inode_newsize_ok(inode, offset + len);
> +		if (ret)
> +			goto out;
> +	}
>  
>  	if (alloc_start > inode->i_size) {
>  		ret = btrfs_cont_expand(inode, i_size_read(inode),
> -- 
> 2.3.4
> 
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