Re: [PATCH 4/4] Btrfs: remove no longer needed range length checks for deduplication

From: Nikolay Borisov <nborisov@suse.com>
To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 4/4] Btrfs: remove no longer needed range length checks for deduplication
Date: Thu, 13 Dec 2018 14:20:16 +0200	[thread overview]
Message-ID: <889d40aa-e517-6e33-875c-e7aba4764440@suse.com> (raw)
In-Reply-To: <20181212180559.15249-5-fdmanana@kernel.org>

On 12.12.18 г. 20:05 ч., fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> Comparing the content of the pages in the range to deduplicate is now done
> by the generic helper generic_remap_file_range_prep(), which takes care of

very minor nit: the checks are performed in generic_remap_checks which
is called by generic_remap_file_range_prep. But even without this change
LGTM.

> ensuring we do not compare/deduplicate undefined data beyond a file's eof
> (range from eof to the next block boundary). So remove these checks which
> are now redundant.
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---
>  fs/btrfs/ioctl.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 4e9efc93340e..3a27efa2b955 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3206,31 +3206,16 @@ static void btrfs_double_inode_lock(struct inode *inode1, struct inode *inode2)
>  	inode_lock_nested(inode2, I_MUTEX_CHILD);
>  }
>  
> -static int btrfs_extent_same_range(struct inode *src, u64 loff, u64 olen,
> +static int btrfs_extent_same_range(struct inode *src, u64 loff, u64 len,
>  				   struct inode *dst, u64 dst_loff)
>  {
> -	u64 bs = BTRFS_I(src)->root->fs_info->sb->s_blocksize;
>  	int ret;
> -	u64 len = olen;
> -
> -	if (loff + len == src->i_size)
> -		len = ALIGN(src->i_size, bs) - loff;
> -	/*
> -	 * For same inode case we don't want our length pushed out past i_size
> -	 * as comparing that data range makes no sense.
> -	 *
> -	 * This effectively means we require aligned extents for the single
> -	 * inode case, whereas the other cases allow an unaligned length so long
> -	 * as it ends at i_size.
> -	 */
> -	if (dst == src && len != olen)
> -		return -EINVAL;
>  
>  	/*
>  	 * Lock destination range to serialize with concurrent readpages().
>  	 */
>  	lock_extent(&BTRFS_I(dst)->io_tree, dst_loff, dst_loff + len - 1);
> -	ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
> +	ret = btrfs_clone(src, dst, loff, len, len, dst_loff, 1);
>  	unlock_extent(&BTRFS_I(dst)->io_tree, dst_loff, dst_loff + len - 1);
>  
>  	return ret;
> 