[PATCH v2 32/50] convert binfmt_misc

[Al Viro <viro@zeniv.linux.org.uk>]

removals are done with locked_recursive_removal(); switch creations to
simple_start_creating()/d_make_persistent()/simple_done_creating() and
take them to a helper (add_entry()), while we are at it - simpler control
flow that way.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/binfmt_misc.c | 69 ++++++++++++++++++++++--------------------------
 1 file changed, 32 insertions(+), 37 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a839f960cd4a..2093f9dcd321 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -765,14 +765,41 @@ static const struct file_operations bm_entry_operations = {
 
 /* /register */
 
+/* add to filesystem */
+static int add_entry(Node *e, struct super_block *sb)
+{
+	struct dentry *dentry = simple_start_creating(sb->s_root, e->name);
+	struct inode *inode;
+	struct binfmt_misc *misc;
+
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
+	inode = bm_get_inode(sb, S_IFREG | 0644);
+	if (unlikely(!inode)) {
+		simple_done_creating(dentry);
+		return -ENOMEM;
+	}
+
+	refcount_set(&e->users, 1);
+	e->dentry = dentry;
+	inode->i_private = e;
+	inode->i_fop = &bm_entry_operations;
+
+	d_make_persistent(dentry, inode);
+	misc = i_binfmt_misc(inode);
+	write_lock(&misc->entries_lock);
+	list_add(&e->list, &misc->entries);
+	write_unlock(&misc->entries_lock);
+	simple_done_creating(dentry);
+	return 0;
+}
+
 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 			       size_t count, loff_t *ppos)
 {
 	Node *e;
-	struct inode *inode;
 	struct super_block *sb = file_inode(file)->i_sb;
-	struct dentry *root = sb->s_root, *dentry;
-	struct binfmt_misc *misc;
 	int err = 0;
 	struct file *f = NULL;
 
@@ -803,39 +830,7 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 		e->interp_file = f;
 	}
 
-	inode_lock(d_inode(root));
-	dentry = lookup_noperm(&QSTR(e->name), root);
-	err = PTR_ERR(dentry);
-	if (IS_ERR(dentry))
-		goto out;
-
-	err = -EEXIST;
-	if (d_really_is_positive(dentry))
-		goto out2;
-
-	inode = bm_get_inode(sb, S_IFREG | 0644);
-
-	err = -ENOMEM;
-	if (!inode)
-		goto out2;
-
-	refcount_set(&e->users, 1);
-	e->dentry = dget(dentry);
-	inode->i_private = e;
-	inode->i_fop = &bm_entry_operations;
-
-	d_instantiate(dentry, inode);
-	misc = i_binfmt_misc(inode);
-	write_lock(&misc->entries_lock);
-	list_add(&e->list, &misc->entries);
-	write_unlock(&misc->entries_lock);
-
-	err = 0;
-out2:
-	dput(dentry);
-out:
-	inode_unlock(d_inode(root));
-
+	err = add_entry(e, sb);
 	if (err) {
 		if (f)
 			filp_close(f, NULL);
@@ -1028,7 +1023,7 @@ static struct file_system_type bm_fs_type = {
 	.name		= "binfmt_misc",
 	.init_fs_context = bm_init_fs_context,
 	.fs_flags	= FS_USERNS_MOUNT,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 };
 MODULE_ALIAS_FS("binfmt_misc");
 
-- 
2.47.3