On fri, 23 Aug 2013 10:34:42 +0200, Stefan Behrens wrote:
> Mitch Harder noticed that the patch 3c64a1a mentioned in the subject
> line was causing a kernel BUG() on snapshot deletion.
>
> The patch was wrong. It did not handle cached roots correctly. The
> check for root_refs == 0 was removed everywhere where
> btrfs_read_fs_root_no_name() had been used to retrieve the root,
> because this check was already dealt with in
> btrfs_read_fs_root_no_name(). But in the case when the root was
> found in the cache, there was no such check.
>
> This patch adds the missing check in the case where the root is
> found in the cache.
>
> Reported-by: Mitch Harder <mitch.harder@xxxxxxxxxxxxxxxx>
> Signed-off-by: Stefan Behrens <sbehrens@xxxxxxxxxxxxxxxx>
> ---
> fs/btrfs/disk-io.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 43ec3c6..7078554 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -1583,8 +1583,11 @@ struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
> ERR_PTR(-ENOENT);
> again:
> root = btrfs_lookup_fs_root(fs_info, location->objectid);
> - if (root)
> + if (root) {
> + if (btrfs_root_refs(&root->root_item) == 0)
> + return ERR_PTR(-ENOENT);
> return root;
> + }
It seems good to me.
Reviewed-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
>
> root = btrfs_read_fs_root(fs_info->tree_root, location);
> if (IS_ERR(root))
>
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