bcachefs: eliminate the uninitialized compilation warning in bch2_reconstruct_snapshots

When compiling the bcachefs-tools, the following compilation warning
is reported:
    libbcachefs/snapshot.c: In function ‘bch2_reconstruct_snapshots’:
    libbcachefs/snapshot.c:915:19: warning: ‘tree_id’ may be used uninitialized in this function [-Wmaybe-uninitialized]
      915 |  snapshot->v.tree = cpu_to_le32(tree_id);
    libbcachefs/snapshot.c:903:6: note: ‘tree_id’ was declared here
      903 |  u32 tree_id;
       |      ^~~~~~~

This is a false alert, because @tree_id is changed in
bch2_snapshot_tree_create after it returns 0. And if this function
returns other value, @tree_id wouldn't be used. Thus there should
be nothing wrong in logical.

Although the report itself is a false alert, we can still make it more
explicit by setting the initial value of @tree_id to 0 (an invalid
tree ID).

Fixes: a292be3b68f3 ("bcachefs: Reconstruct missing snapshot nodes")
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index 2368218070d45c0db66b3874d4e7f03bb353e641..3aa4686cc71fcc318516a35e2f2e61dda54fae33 100644 (file)
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -900,7 +900,8 @@ static int check_snapshot_exists(struct btree_trans *trans, u32 id)
        if (bch2_snapshot_equiv(c, id))
                return 0;
 
-       u32 tree_id;
+       /* 0 is an invalid tree ID */
+       u32 tree_id = 0;
        int ret = bch2_snapshot_tree_create(trans, id, 0, &tree_id);
        if (ret)
                return ret;