Re: [PATCH 2/9] btrfs: Fix tail space processing in find_free_dev_extent()

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

On Fri, Apr 03, 2015 at 08:11:57PM +0800, Zhaolei wrote:
> From: Zhao Lei <zhaolei@cn.fujitsu.com>
> 
> It is another reason for NO_SPACE case.
> 
> When we found enough free space in loop and saved them to
> max_hole_start/size before, and tail space contains pending extent,
> origional innocent max_hole_start/size are reset in retry.
> 
> As a result, find_free_dev_extent() returns less space than it can,
> and cause NO_SPACE in user program.

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

> 
> Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
> ---
>  fs/btrfs/volumes.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 8222f6f..586824a 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1136,11 +1136,11 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans,
>  	path = btrfs_alloc_path();
>  	if (!path)
>  		return -ENOMEM;
> -again:
> +
>  	max_hole_start = search_start;
>  	max_hole_size = 0;
> -	hole_size = 0;
>  
> +again:
>  	if (search_start >= search_end || device->is_tgtdev_for_dev_replace) {
>  		ret = -ENOSPC;
>  		goto out;
> @@ -1233,21 +1233,23 @@ next:
>  	 * allocated dev extents, and when shrinking the device,
>  	 * search_end may be smaller than search_start.
>  	 */
> -	if (search_end > search_start)
> +	if (search_end > search_start) {
>  		hole_size = search_end - search_start;
>  
> -	if (hole_size > max_hole_size) {
> -		max_hole_start = search_start;
> -		max_hole_size = hole_size;
> -	}
> +		if (contains_pending_extent(trans, device, &search_start,
> +					    hole_size)) {
> +			btrfs_release_path(path);
> +			goto again;
> +		}
>  
> -	if (contains_pending_extent(trans, device, &search_start, hole_size)) {
> -		btrfs_release_path(path);
> -		goto again;
> +		if (hole_size > max_hole_size) {
> +			max_hole_start = search_start;
> +			max_hole_size = hole_size;
> +		}
>  	}
>  
>  	/* See above. */
> -	if (hole_size < num_bytes)
> +	if (max_hole_size < num_bytes)
>  		ret = -ENOSPC;
>  	else
>  		ret = 0;
> -- 
> 1.8.5.1
> 
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