f2fs: fix handling orphan inodes

This patch fixes mishandling of the sbi->n_orphans variable.

If users request lots of f2fs_unlink(), check_orphan_space() could be contended.
In such the case, sbi->n_orphans can be read incorrectly so that f2fs_unlink()
would fall into the wrong state which results in the failure of
add_orphan_inode().

So, let's increment sbi->n_orphans virtually prior to the actual orphan inode
stuffs. After that, let's release sbi->n_orphans by calling release_orphan_inode
or remove_orphan_inode.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/checkpoint.c

@@ -182,7 +182,7 @@ const struct address_space_operations f2fs_meta_aops = {
 	.set_page_dirty	= f2fs_set_meta_page_dirty,
 };
 
-int check_orphan_space(struct f2fs_sb_info *sbi)
+int acquire_orphan_inode(struct f2fs_sb_info *sbi)
 {
 	unsigned int max_orphans;
 	int err = 0;
@@ -197,10 +197,19 @@ int check_orphan_space(struct f2fs_sb_info *sbi)
 	mutex_lock(&sbi->orphan_inode_mutex);
 	if (sbi->n_orphans >= max_orphans)
 		err = -ENOSPC;
+	else
+		sbi->n_orphans++;
 	mutex_unlock(&sbi->orphan_inode_mutex);
 	return err;
 }
 
+void release_orphan_inode(struct f2fs_sb_info *sbi)
+{
+	mutex_lock(&sbi->orphan_inode_mutex);
+	sbi->n_orphans--;
+	mutex_unlock(&sbi->orphan_inode_mutex);
+}
+
 void add_orphan_inode(struct f2fs_sb_info *sbi, nid_t ino)
 {
 	struct list_head *head, *this;
@@ -229,8 +238,6 @@ void add_orphan_inode(struct f2fs_sb_info *sbi, nid_t ino)
 		list_add(&new->list, this->prev);
 	else
 		list_add_tail(&new->list, head);
-
-	sbi->n_orphans++;
 out:
 	mutex_unlock(&sbi->orphan_inode_mutex);
 }

fs/f2fs/dir.c

@@ -572,6 +572,8 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
 
 		if (inode->i_nlink == 0)
 			add_orphan_inode(sbi, inode->i_ino);
+		else
+			release_orphan_inode(sbi);
 	}
 
 	if (bit_pos == NR_DENTRY_IN_BLOCK) {

fs/f2fs/f2fs.h

@@ -1044,7 +1044,8 @@ void destroy_segment_manager(struct f2fs_sb_info *);
 struct page *grab_meta_page(struct f2fs_sb_info *, pgoff_t);
 struct page *get_meta_page(struct f2fs_sb_info *, pgoff_t);
 long sync_meta_pages(struct f2fs_sb_info *, enum page_type, long);
-int check_orphan_space(struct f2fs_sb_info *);
+int acquire_orphan_inode(struct f2fs_sb_info *);
+void release_orphan_inode(struct f2fs_sb_info *);
 void add_orphan_inode(struct f2fs_sb_info *, nid_t);
 void remove_orphan_inode(struct f2fs_sb_info *, nid_t);
 int recover_orphan_inodes(struct f2fs_sb_info *);

fs/f2fs/namei.c

@@ -239,7 +239,7 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry)
 	if (!de)
 		goto fail;
 
-	err = check_orphan_space(sbi);
+	err = acquire_orphan_inode(sbi);
 	if (err) {
 		kunmap(page);
 		f2fs_put_page(page, 0);
@@ -393,7 +393,7 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	struct inode *old_inode = old_dentry->d_inode;
 	struct inode *new_inode = new_dentry->d_inode;
 	struct page *old_dir_page;
-	struct page *old_page;
+	struct page *old_page, *new_page;
 	struct f2fs_dir_entry *old_dir_entry = NULL;
 	struct f2fs_dir_entry *old_entry;
 	struct f2fs_dir_entry *new_entry;
@@ -415,7 +415,6 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	ilock = mutex_lock_op(sbi);
 
 	if (new_inode) {
-		struct page *new_page;
 
 		err = -ENOTEMPTY;
 		if (old_dir_entry && !f2fs_empty_dir(new_inode))
@@ -427,9 +426,13 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		if (!new_entry)
 			goto out_dir;
 
+		err = acquire_orphan_inode(sbi);
+		if (err)
+			goto put_out_dir;
+
 		if (update_dent_inode(old_inode, &new_dentry->d_name)) {
-			f2fs_put_page(new_page, 1);
-			goto out_dir;
+			release_orphan_inode(sbi);
+			goto put_out_dir;
 		}
 
 		f2fs_set_link(new_dir, new_entry, new_page, old_inode);
@@ -438,8 +441,12 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		if (old_dir_entry)
 			drop_nlink(new_inode);
 		drop_nlink(new_inode);
+
 		if (!new_inode->i_nlink)
 			add_orphan_inode(sbi, new_inode->i_ino);
+		else
+			release_orphan_inode(sbi);
+
 		update_inode_page(new_inode);
 	} else {
 		err = f2fs_add_link(new_dentry, old_inode);
@@ -472,6 +479,8 @@ static int f2fs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	mutex_unlock_op(sbi, ilock);
 	return 0;
 
+put_out_dir:
+	f2fs_put_page(new_page, 1);
 out_dir:
 	if (old_dir_entry) {
 		kunmap(old_dir_page);