Merge tag 'configfs-6.13-2024-11-19' of git://git.infradead.org/users/hch/configfs

Pull configfs updates from Christoph Hellwig:

 - remove unused code (Dr. David Alan Gilbert)

 - improve item creation performance (Seamus Connor)

* tag 'configfs-6.13-2024-11-19' of git://git.infradead.org/users/hch/configfs:
  configfs: improve item creation performance
  configfs: remove unused configfs_hash_and_remove

Author: torvalds

fs/configfs/configfs_internal.h

@@ -55,6 +55,8 @@ struct configfs_dirent {
 #define CONFIGFS_USET_IN_MKDIR	0x0200
 #define CONFIGFS_USET_CREATING	0x0400
 #define CONFIGFS_NOT_PINNED	(CONFIGFS_ITEM_ATTR | CONFIGFS_ITEM_BIN_ATTR)
+#define CONFIGFS_PINNED \
+	(CONFIGFS_ROOT | CONFIGFS_DIR | CONFIGFS_ITEM_LINK)
 
 extern struct mutex configfs_symlink_mutex;
 extern spinlock_t configfs_dirent_lock;
@@ -73,8 +75,6 @@ extern int configfs_make_dirent(struct configfs_dirent *, struct dentry *,
 				void *, umode_t, int, struct configfs_fragment *);
 extern int configfs_dirent_is_ready(struct configfs_dirent *);
 
-extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
-
 extern const unsigned char * configfs_get_name(struct configfs_dirent *sd);
 extern void configfs_drop_dentry(struct configfs_dirent *sd, struct dentry *parent);
 extern int configfs_setattr(struct mnt_idmap *idmap,

fs/configfs/dir.c

@@ -207,7 +207,17 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *paren
 		return ERR_PTR(-ENOENT);
 	}
 	sd->s_frag = get_fragment(frag);
-	list_add(&sd->s_sibling, &parent_sd->s_children);
+
+	/*
+	 * configfs_lookup scans only for unpinned items. s_children is
+	 * partitioned so that configfs_lookup can bail out early.
+	 * CONFIGFS_PINNED and CONFIGFS_NOT_PINNED are not symmetrical.  readdir
+	 * cursors still need to be inserted at the front of the list.
+	 */
+	if (sd->s_type & CONFIGFS_PINNED)
+		list_add_tail(&sd->s_sibling, &parent_sd->s_children);
+	else
+		list_add(&sd->s_sibling, &parent_sd->s_children);
 	spin_unlock(&configfs_dirent_lock);
 
 	return sd;
@@ -220,10 +230,11 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *paren
  *
  * called with parent inode's i_mutex held
  */
-static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
-				  const unsigned char *new)
+static int configfs_dirent_exists(struct dentry *dentry)
 {
-	struct configfs_dirent * sd;
+	struct configfs_dirent *parent_sd = dentry->d_parent->d_fsdata;
+	const unsigned char *new = dentry->d_name.name;
+	struct configfs_dirent *sd;
 
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_element) {
@@ -289,10 +300,6 @@ static int configfs_create_dir(struct config_item *item, struct dentry *dentry,
 
 	BUG_ON(!item);
 
-	error = configfs_dirent_exists(p->d_fsdata, dentry->d_name.name);
-	if (unlikely(error))
-		return error;
-
 	error = configfs_make_dirent(p->d_fsdata, dentry, item, mode,
 				     CONFIGFS_DIR | CONFIGFS_USET_CREATING,
 				     frag);
@@ -451,6 +458,18 @@ static struct dentry * configfs_lookup(struct inode *dir,
 
 	spin_lock(&configfs_dirent_lock);
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
+
+		/*
+		 * s_children is partitioned, see configfs_new_dirent. The first
+		 * pinned item indicates we can stop scanning.
+		 */
+		if (sd->s_type & CONFIGFS_PINNED)
+			break;
+
+		/*
+		 * Note: CONFIGFS_PINNED and CONFIGFS_NOT_PINNED are asymmetric.
+		 * there may be a readdir cursor in this list
+		 */
 		if ((sd->s_type & CONFIGFS_NOT_PINNED) &&
 		    !strcmp(configfs_get_name(sd), dentry->d_name.name)) {
 			struct configfs_attribute *attr = sd->s_element;
@@ -1885,8 +1904,11 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 	if (dentry) {
 		d_add(dentry, NULL);
 
-		err = configfs_attach_group(sd->s_element, &group->cg_item,
-					    dentry, frag);
+		err = configfs_dirent_exists(dentry);
+		if (!err)
+			err = configfs_attach_group(sd->s_element,
+						    &group->cg_item,
+						    dentry, frag);
 		if (err) {
 			BUG_ON(d_inode(dentry));
 			d_drop(dentry);

fs/configfs/inode.c

@@ -216,28 +216,3 @@ void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
 			spin_unlock(&dentry->d_lock);
 	}
 }
-
-void configfs_hash_and_remove(struct dentry * dir, const char * name)
-{
-	struct configfs_dirent * sd;
-	struct configfs_dirent * parent_sd = dir->d_fsdata;
-
-	if (d_really_is_negative(dir))
-		/* no inode means this hasn't been made visible yet */
-		return;
-
-	inode_lock(d_inode(dir));
-	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-		if (!sd->s_element)
-			continue;
-		if (!strcmp(configfs_get_name(sd), name)) {
-			spin_lock(&configfs_dirent_lock);
-			list_del_init(&sd->s_sibling);
-			spin_unlock(&configfs_dirent_lock);
-			configfs_drop_dentry(sd, dir);
-			configfs_put(sd);
-			break;
-		}
-	}
-	inode_unlock(d_inode(dir));
-}