smb/server: use end_removing_noperm for for target of smb2_create_link()

Sometimes smb2_create_link() needs to remove the target before creating
the link.
It uses ksmbd_vfs_kern_locked(), and is the only user of that interface.

To match the new naming, that function is changed to
ksmbd_vfs_kern_start_removing(), and related functions or flags are also
renamed.

The lock actually happens in ksmbd_vfs_path_lookup() and that is changed
to use start_removing_noperm() - permission to perform lookup in the
parent was already checked in vfs_path_parent_lookup().

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20251113002050.676694-8-neilb@ownmail.net
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

fs/smb/server/smb2pdu.c

@@ -6084,8 +6084,8 @@ static int smb2_create_link(struct ksmbd_work *work,
 	}
 
 	ksmbd_debug(SMB, "target name is %s\n", target_name);
-	rc = ksmbd_vfs_kern_path_locked(work, link_name, LOOKUP_NO_SYMLINKS,
-					&path, 0);
+	rc = ksmbd_vfs_kern_path_start_removing(work, link_name, LOOKUP_NO_SYMLINKS,
+						&path, 0);
 	if (rc) {
 		if (rc != -ENOENT)
 			goto out;
@@ -6103,7 +6103,7 @@ static int smb2_create_link(struct ksmbd_work *work,
 			ksmbd_debug(SMB, "link already exists\n");
 			goto out;
 		}
-		ksmbd_vfs_kern_path_unlock(&path);
+		ksmbd_vfs_kern_path_end_removing(&path);
 	}
 	rc = ksmbd_vfs_link(work, target_name, link_name);
 	if (rc)

fs/smb/server/vfs.c

@@ -69,7 +69,7 @@ int ksmbd_vfs_lock_parent(struct dentry *parent, struct dentry *child)
 
 static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
 				 char *pathname, unsigned int flags,
-				 struct path *path, bool do_lock)
+				 struct path *path, bool for_remove)
 {
 	struct qstr last;
 	struct filename *filename __free(putname) = NULL;
@@ -99,22 +99,20 @@ static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
 		return -ENOENT;
 	}
 
-	if (do_lock) {
+	if (for_remove) {
 		err = mnt_want_write(path->mnt);
 		if (err) {
 			path_put(path);
 			return -ENOENT;
 		}
 
-		inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
-		d = lookup_one_qstr_excl(&last, path->dentry, 0);
+		d = start_removing_noperm(path->dentry, &last);
 
 		if (!IS_ERR(d)) {
 			dput(path->dentry);
 			path->dentry = d;
 			return 0;
 		}
-		inode_unlock(path->dentry->d_inode);
 		mnt_drop_write(path->mnt);
 		path_put(path);
 		return -ENOENT;
@@ -1207,15 +1205,15 @@ static int ksmbd_vfs_lookup_in_dir(const struct path *dir, char *name,
 static
 int __ksmbd_vfs_kern_path(struct ksmbd_work *work, char *filepath,
 			  unsigned int flags,
-			  struct path *path, bool caseless, bool do_lock)
+			  struct path *path, bool caseless, bool for_remove)
 {
 	struct ksmbd_share_config *share_conf = work->tcon->share_conf;
 	struct path parent_path;
 	size_t path_len, remain_len;
 	int err;
 
 retry:
-	err = ksmbd_vfs_path_lookup(share_conf, filepath, flags, path, do_lock);
+	err = ksmbd_vfs_path_lookup(share_conf, filepath, flags, path, for_remove);
 	if (!err || !caseless)
 		return err;
 
@@ -1286,7 +1284,7 @@ int ksmbd_vfs_kern_path(struct ksmbd_work *work, char *filepath,
 }
 
 /**
- * ksmbd_vfs_kern_path_locked() - lookup a file and get path info
+ * ksmbd_vfs_kern_path_start_remove() - lookup a file and get path info prior to removal
  * @work:		work
  * @filepath:		file path that is relative to share
  * @flags:		lookup flags
@@ -1298,20 +1296,19 @@ int ksmbd_vfs_kern_path(struct ksmbd_work *work, char *filepath,
  * filesystem will have been gained.
  * Return:	0 on if file was found, otherwise error
  */
-int ksmbd_vfs_kern_path_locked(struct ksmbd_work *work, char *filepath,
-			       unsigned int flags,
-			       struct path *path, bool caseless)
+int ksmbd_vfs_kern_path_start_removing(struct ksmbd_work *work, char *filepath,
+				       unsigned int flags,
+				       struct path *path, bool caseless)
 {
 	return __ksmbd_vfs_kern_path(work, filepath, flags, path,
 				     caseless, true);
 }
 
-void ksmbd_vfs_kern_path_unlock(const struct path *path)
+void ksmbd_vfs_kern_path_end_removing(const struct path *path)
 {
-	/* While lock is still held, ->d_parent is safe */
-	inode_unlock(d_inode(path->dentry->d_parent));
+	end_removing(path->dentry);
 	mnt_drop_write(path->mnt);
-	path_put(path);
+	mntput(path->mnt);
 }
 
 struct dentry *ksmbd_vfs_kern_path_create(struct ksmbd_work *work,

fs/smb/server/vfs.h

@@ -120,10 +120,10 @@ int ksmbd_vfs_remove_xattr(struct mnt_idmap *idmap,
 int ksmbd_vfs_kern_path(struct ksmbd_work *work, char *name,
 			unsigned int flags,
 			struct path *path, bool caseless);
-int ksmbd_vfs_kern_path_locked(struct ksmbd_work *work, char *name,
-			       unsigned int flags,
-			       struct path *path, bool caseless);
-void ksmbd_vfs_kern_path_unlock(const struct path *path);
+int ksmbd_vfs_kern_path_start_removing(struct ksmbd_work *work, char *name,
+				       unsigned int flags,
+				       struct path *path, bool caseless);
+void ksmbd_vfs_kern_path_end_removing(const struct path *path);
 struct dentry *ksmbd_vfs_kern_path_create(struct ksmbd_work *work,
 					  const char *name,
 					  unsigned int flags,