Re: [PATCH] btrfs-progs: properly exclude leaves for lowmem

From: Su Yue <l@damenly.su>
To: Josef Bacik <josef@toxicpanda.com>
Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH] btrfs-progs: properly exclude leaves for lowmem
Date: Wed, 06 Jan 2021 09:42:24 +0800	[thread overview]
Message-ID: <v9calu2o.fsf@damenly.su> (raw)
In-Reply-To: <845796bfab85f02919d64908b63f3f7201a2abb3.1609882807.git.josef@toxicpanda.com>

On Wed 06 Jan 2021 at 05:40, Josef Bacik <josef@toxicpanda.com> 
wrote:

> The lowmem mode excludes all referenced blocks from the 
> allocator in
> order to avoid accidentally overwriting blocks while fixing the 
> file
> system.  However for leaves it wouldn't exclude anything, it 
> would just
> pin them down, which gets cleaned up on transaction commit. 
> We're safe
> for the first modification, but subsequent modifications could 
> blow up
> in our face.  Fix this by properly excluding leaves as well as 
> all of
> the nodes.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>

LGTM.
Reviewed-by: Su Yue <l@damenly.su>
> ---
>  check/mode-common.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/check/mode-common.c b/check/mode-common.c
> index a6489191..ef77b060 100644
> --- a/check/mode-common.c
> +++ b/check/mode-common.c
> @@ -667,8 +667,12 @@ static int traverse_tree_blocks(struct 
> extent_buffer *eb, int tree_root, int pin
>
>  			/* If we aren't the tree root don't read the block */
>  			if (level == 1 && !tree_root) {
> -				btrfs_pin_extent(gfs_info, bytenr,
> -						 gfs_info->nodesize);
>
> +				if (pin)
> +					btrfs_pin_extent(gfs_info, bytenr,
> +							 gfs_info->nodesize);
> +				else
> +					set_extent_dirty(tree, bytenr,
> +							 gfs_info->nodesize);
>  				continue;
>  			}