ceph: return the correct dentry on mkdir

ceph already splices the correct dentry (in splice_dentry()) from the
result of mkdir but does nothing more with it.

Now that ->mkdir can return a dentry, return the correct dentry.

Note that previously ceph_mkdir() could call
   ceph_init_inode_acls()
on the inode from the wrong dentry, which would be NULL.  This
is safe as ceph_init_inode_acls() checks for NULL, but is not
strictly correct.  With this patch, the inode for the returned dentry
is passed to ceph_init_inode_acls().

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250227013949.536172-4-neilb@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

fs/ceph/dir.c

@@ -1099,6 +1099,7 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	struct ceph_client *cl = mdsc->fsc->client;
 	struct ceph_mds_request *req;
 	struct ceph_acl_sec_ctx as_ctx = {};
+	struct dentry *ret;
 	int err;
 	int op;
 
@@ -1116,32 +1117,32 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 		      ceph_vinop(dir), dentry, dentry, mode);
 		op = CEPH_MDS_OP_MKDIR;
 	} else {
-		err = -EROFS;
+		ret = ERR_PTR(-EROFS);
 		goto out;
 	}
 
 	if (op == CEPH_MDS_OP_MKDIR &&
 	    ceph_quota_is_max_files_exceeded(dir)) {
-		err = -EDQUOT;
+		ret = ERR_PTR(-EDQUOT);
 		goto out;
 	}
 	if ((op == CEPH_MDS_OP_MKSNAP) && IS_ENCRYPTED(dir) &&
 	    !fscrypt_has_encryption_key(dir)) {
-		err = -ENOKEY;
+		ret = ERR_PTR(-ENOKEY);
 		goto out;
 	}
 
 
 	req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
 	if (IS_ERR(req)) {
-		err = PTR_ERR(req);
+		ret = ERR_CAST(req);
 		goto out;
 	}
 
 	mode |= S_IFDIR;
 	req->r_new_inode = ceph_new_inode(dir, dentry, &mode, &as_ctx);
 	if (IS_ERR(req->r_new_inode)) {
-		err = PTR_ERR(req->r_new_inode);
+		ret = ERR_CAST(req->r_new_inode);
 		req->r_new_inode = NULL;
 		goto out_req;
 	}
@@ -1165,15 +1166,22 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	    !req->r_reply_info.head->is_target &&
 	    !req->r_reply_info.head->is_dentry)
 		err = ceph_handle_notrace_create(dir, dentry);
+	ret = ERR_PTR(err);
 out_req:
+	if (!IS_ERR(ret) && req->r_dentry != dentry)
+		/* Some other dentry was spliced in */
+		ret = dget(req->r_dentry);
 	ceph_mdsc_put_request(req);
 out:
-	if (!err)
+	if (!IS_ERR(ret)) {
+		if (ret)
+			dentry = ret;
 		ceph_init_inode_acls(d_inode(dentry), &as_ctx);
-	else
+	} else {
 		d_drop(dentry);
+	}
 	ceph_release_acl_sec_ctx(&as_ctx);
-	return ERR_PTR(err);
+	return ret;
 }
 
 static int ceph_link(struct dentry *old_dentry, struct inode *dir,