Re: [PATCH 1/7] Btrfs: replace BUG() with WARN_ONCE in raid56

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 05/14/2016 08:06 AM, Liu Bo wrote:
> This BUG() has been triggered by a fuzz testing image, but in fact
> btrfs can handle this gracefully by returning -EIO.
>
> Thus, use WARN_ONCE for warning purpose and don't leave a possible
> kernel panic.
>
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> ---
>  fs/btrfs/raid56.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> index 0b7792e..863f7fe 100644
> --- a/fs/btrfs/raid56.c
> +++ b/fs/btrfs/raid56.c
> @@ -2139,7 +2139,7 @@ int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
>
>  	rbio->faila = find_logical_bio_stripe(rbio, bio);
>  	if (rbio->faila == -1) {
> -		BUG();
> +		WARN_ONCE(1, KERN_WARNING "rbio->faila is -1\n");

Just a personal idea, it would be much better if we can use 
btrfs_info/error/warn() to output the warning message.
This would help to locate the fs causing the problem, if there are 
several btrfs mounted.

Like:
        btrfs_warn(root->fs_info, "rbio->faia is -1");
        WARN_ON(1);

Or adds a new helper like btrfs_dump_warn()?

Thanks,
Qu

>  		if (generic_io)
>  			btrfs_put_bbio(bbio);
>  		kfree(rbio);
>