Re: [PATCH v2] btrfs: Remove redundant assignment of slot and leaf

Filipe Manana
2022-01-05T16:11:40Z

On Wed, Jan 05, 2022 at 11:07:58PM +0800, Jiapeng Chong wrote:
> From: chongjiapeng <jiapeng.chong@linux.alibaba.com>
>
> slot and leaf are being initialized to path->slots[0] and
> path->nodes[0], but this is never read as slot and leaf
> is overwritten later on. Remove the redundant assignment.
>
> Cleans up the following clang-analyzer warning:
>
> fs/btrfs/tree-log.c:6125:7: warning: Value stored to 'slot' during its
> initialization is never read [clang-analyzer-deadcode.DeadStores].
>
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: chongjiapeng <jiapeng.chong@linux.alibaba.com>
> ---
> Changes in v2:
> -Remove redundant assignment of leaf.
>
> fs/btrfs/tree-log.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
> index 4b89ac769347..d99cda0acd95 100644
> --- a/fs/btrfs/tree-log.c
> +++ b/fs/btrfs/tree-log.c
> @@ -6188,8 +6188,6 @@ static int log_new_ancestors(struct btrfs_trans_handle *trans,
> if (ret < 0)
> return ret;
>
> - leaf = path->nodes[0];
> - slot = path->slots[0];

No, this is not correct.

Right before those assignments we called btrfs_search_slot(), which updates
path->nodes and path->slots, and we need those updated values below.

The redundant assignments are not these two, but instead the ones when the
variables are declared at the top of the loop:

struct extent_buffer *leaf = path->nodes[0];
int slot = path->slots[0];

Thanks.

> if (slot >= btrfs_header_nritems(leaf)) {
> ret = btrfs_next_leaf(root, path);
> if (ret < 0)
> --
> 2.19.1.6.gb485710b
>