Re: [PATCH 3/4] btrfs: fix force usage in inc_block_group_ro

[Nikolay Borisov <nborisov@suse.com>]

On 25.11.19 г. 16:40 ч., Josef Bacik wrote:
> For some reason we've translated the do_chunk_alloc that goes into
> btrfs_inc_block_group_ro to force in inc_block_group_ro, but these are
> two different things.
> 
> force for inc_block_group_ro is used when we are forcing the block group
> read only no matter what, for example when the underlying chunk is
> marked read only.  We need to not do the space check here as this block
> group needs to be read only.
> 
> btrfs_inc_block_group_ro() has a do_chunk_alloc flag that indicates that
> we need to pre-allocate a chunk before marking the block group read
> only.  This has nothing to do with forcing, and in fact we _always_ want
> to do the space check in this case, so unconditionally pass false for
> force in this case.
> 
> Then fixup inc_block_group_ro to honor force as it's expected and
> documented to do.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/block-group.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index db539bfc5a52..3ffbc2e0af21 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -1190,8 +1190,10 @@ static int inc_block_group_ro(struct btrfs_block_group *cache, int force)
>  	spin_lock(&sinfo->lock);
>  	spin_lock(&cache->lock);
>  
> -	if (cache->ro) {
> +	if (cache->ro || force) {
>  		cache->ro++;
> +		if (list_empty(&cache->ro_list))
> +			list_add_tail(&cache->ro_list, &sinfo->ro_bgs);

nit: This only makes sense in the case of force e.g. just to make it
clearer perhahps the check can be modified to if (force || list_empty)?

>  		ret = 0;
>  		goto out;
>  	}
> @@ -2063,7 +2065,7 @@ int btrfs_inc_block_group_ro(struct btrfs_block_group *cache,
>  		}
>  	}
>  
> -	ret = inc_block_group_ro(cache, !do_chunk_alloc);
> +	ret = inc_block_group_ro(cache, false);
>  	if (!do_chunk_alloc)
>  		goto unlock_out;
>  	if (!ret)
>