Re: [PATCH] btrfs: fix crash when no drive supports DISCARD

[Li Dongyang <lidongyang@novell.com>]

On Wednesday, May 18, 2011 12:00:31 AM David Sterba wrote:
> xfstests/013 crashes when the test partition is mounted with -o discard:
> 
> walk_up_log_tree
>   btrfs_free_reserved_extent
>     btrfs_discard_extent
>       return -EOPNOTSUPP
>     BUG_ON ret
> 
> btrfs_discard_extent() should be fine when drive does not support the
> DISCARD operation and filter the EOPNOTSUPP retcode, but currently it
> does this only when some bytes were succesfully discarded.
> 
> Signed-off-by: David Sterba <dsterba@suse.cz>
> CC: stable@kernel.org
> ---
>  fs/btrfs/extent-tree.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 9ee6bd5..feab2ab 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -1790,7 +1790,7 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
>  		}
>  		kfree(multi);
>  	}
> -	if (discarded_bytes && ret == -EOPNOTSUPP)
> +	if (ret == -EOPNOTSUPP)
>  		ret = 0;
>  
>  	if (actual_bytes)
> 
Thanks for the fix, I thought EOPNOTSUPP could be useful by the caller that time, and maybe we could do somthing
like remove the discard mount_opt in the fs_info so we can avoid calling it again.