configfs: fold configfs_attach_attr into configfs_lookup

mainline inclusion
from mainline-v5.15-rc1
commit d07f132a
category: bugfix
bugzilla: 187567, https://gitee.com/openeuler/kernel/issues/I5PK1G
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/configfs/dir.c?h=v6.0-rc3&id=d07f132a225c013e59aa77f514ad9211ecab82ee

--------------------------------

This makes it more clear what gets added to the dcache and prepares
for an additional locking fix.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NZhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/configfs/dir.c

@@ -55,7 +55,7 @@ static void configfs_d_iput(struct dentry * dentry,
 		/*
 		 * Set sd->s_dentry to null only when this dentry is the one
 		 * that is going to be killed.  Otherwise configfs_d_iput may
-		 * run just after configfs_attach_attr and set sd->s_dentry to
+		 * run just after configfs_lookup and set sd->s_dentry to
 		 * NULL even it's still in use.
 		 */
 		if (sd->s_dentry == dentry)
@@ -426,44 +426,13 @@ static void configfs_remove_dir(struct config_item * item)
 	dput(dentry);
 }
 
-
-/* attaches attribute's configfs_dirent to the dentry corresponding to the
- * attribute file
- */
-static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
-{
-	struct configfs_attribute * attr = sd->s_element;
-	struct inode *inode;
-
-	spin_lock(&configfs_dirent_lock);
-	dentry->d_fsdata = configfs_get(sd);
-	sd->s_dentry = dentry;
-	spin_unlock(&configfs_dirent_lock);
-
-	inode = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG);
-	if (IS_ERR(inode)) {
-		configfs_put(sd);
-		return PTR_ERR(inode);
-	}
-	if (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) {
-		inode->i_size = 0;
-		inode->i_fop = &configfs_bin_file_operations;
-	} else {
-		inode->i_size = PAGE_SIZE;
-		inode->i_fop = &configfs_file_operations;
-	}
-	d_add(dentry, inode);
-	return 0;
-}
-
 static struct dentry * configfs_lookup(struct inode *dir,
 				       struct dentry *dentry,
 				       unsigned int flags)
 {
 	struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 	struct configfs_dirent * sd;
-	int found = 0;
-	int err;
+	struct inode *inode = NULL;
 
 	if (dentry->d_name.len > NAME_MAX)
 		return ERR_PTR(-ENAMETOOLONG);
@@ -480,28 +449,34 @@ static struct dentry * configfs_lookup(struct inode *dir,
 		return ERR_PTR(-ENOENT);
 
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-		if (sd->s_type & CONFIGFS_NOT_PINNED) {
-			const unsigned char * name = configfs_get_name(sd);
+		if ((sd->s_type & CONFIGFS_NOT_PINNED) &&
+		    !strcmp(configfs_get_name(sd), dentry->d_name.name)) {
+			struct configfs_attribute *attr = sd->s_element;
+			umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
 
-			if (strcmp(name, dentry->d_name.name))
-				continue;
+			spin_lock(&configfs_dirent_lock);
+			dentry->d_fsdata = configfs_get(sd);
+			sd->s_dentry = dentry;
+			spin_unlock(&configfs_dirent_lock);
 
-			found = 1;
-			err = configfs_attach_attr(sd, dentry);
+			inode = configfs_create(dentry, mode);
+			if (IS_ERR(inode)) {
+				configfs_put(sd);
+				return ERR_CAST(inode);
+			}
+			if (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) {
+				inode->i_size = 0;
+				inode->i_fop = &configfs_bin_file_operations;
+			} else {
+				inode->i_size = PAGE_SIZE;
+				inode->i_fop = &configfs_file_operations;
+			}
 			break;
 		}
 	}
 
-	if (!found) {
-		/*
-		 * If it doesn't exist and it isn't a NOT_PINNED item,
-		 * it must be negative.
-		 */
-		d_add(dentry, NULL);
-		return NULL;
-	}
-
-	return ERR_PTR(err);
+	d_add(dentry, inode);
+	return NULL;
 }
 
 /*