Re: [PATCH v2 02/12] btrfs-progs: do not infinite loop on corrupt keys with lowmem mode

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

On 2021/8/19 上午5:33, Josef Bacik wrote:
> By enabling the lowmem checks properly I uncovered the case where test
> 007 will infinite loop at the detection stage.  This is because when
> checking the inode item we will just btrfs_next_item(), and because we
> ignore check tree block failures at read time we don't get an -EIO from
> btrfs_next_leaf.  Generally what check usually does is validate the
> leaves/nodes as we hit them, but in this case we're not doing that.  Fix
> this by checking the leaf if we move to the next one and if it fails
> bail.  This allows us to pass the 007 test with lowmem.

Doesn't this mean btrfs_next_item() is not doing what it should do?

Normally we would expect btrfs_next_item() to return -EIO other than
manually checking the returned leaf.

Thanks,
Qu
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
>   check/mode-lowmem.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
> index 323e66bc..7fc7d467 100644
> --- a/check/mode-lowmem.c
> +++ b/check/mode-lowmem.c
> @@ -2675,6 +2675,15 @@ static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path)
>   	while (1) {
>   		btrfs_item_key_to_cpu(path->nodes[0], &last_key, path->slots[0]);
>   		ret = btrfs_next_item(root, path);
> +
> +		/*
> +		 * New leaf, we need to check it and see if it's valid, if not
> +		 * we need to bail otherwise we could end up stuck.
> +		 */
> +		if (path->slots[0] == 0 &&
> +		    btrfs_check_leaf(gfs_info, NULL, path->nodes[0]))
> +			ret = -EIO;
> +
>   		if (ret < 0) {
>   			/* out will fill 'err' rusing current statistics */
>   			goto out;
>