f2fs: declare nested quota_sem and remove unnecessary sems

1.
f2fs_quota_sync
-> down_read(&sbi->quota_sem)
-> dquot_writeback_dquots
-> f2fs_dquot_commit
-> down_read(&sbi->quota_sem)

2.
f2fs_quota_sync
-> down_read(&sbi->quota_sem)
-> f2fs_write_data_pages
-> f2fs_write_single_data_page
-> down_write(&F2FS_I(inode)->i_sem)

f2fs_mkdir
-> f2fs_do_add_link
-> down_write(&F2FS_I(inode)->i_sem)
-> f2fs_init_inode_metadata
-> f2fs_new_node_page
-> dquot_alloc_inode
-> f2fs_dquot_mark_dquot_dirty
-> down_read(&sbi->quota_sem)

Signed-off-by: Jaegeuk Kim <[e-mail]>

fs/f2fs/super.c

···
 	struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
 	int ret;
 
-	down_read(&sbi->quota_sem);
+	down_read_nested(&sbi->quota_sem, SINGLE_DEPTH_NESTING);
 	ret = dquot_commit(dquot);
 	if (ret < 0)
 		set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
···
 static int f2fs_dquot_release(struct dquot *dquot)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
-	int ret;
+	int ret = dquot_release(dquot);
 
-	down_read(&sbi->quota_sem);
-	ret = dquot_release(dquot);
 	if (ret < 0)
 		set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
-	up_read(&sbi->quota_sem);
 	return ret;
 }
 
···
 {
 	struct super_block *sb = dquot->dq_sb;
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
-	int ret;
-
-	down_read(&sbi->quota_sem);
-	ret = dquot_mark_dquot_dirty(dquot);
+	int ret = dquot_mark_dquot_dirty(dquot);
 
 	/* if we are using journalled quota */
 	if (is_journalled_quota(sbi))
 		set_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
 
-	up_read(&sbi->quota_sem);
 	return ret;
 }
 
 static int f2fs_dquot_commit_info(struct super_block *sb, int type)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
-	int ret;
+	int ret = dquot_commit_info(sb, type);
 
-	down_read(&sbi->quota_sem);
-	ret = dquot_commit_info(sb, type);
 	if (ret < 0)
 		set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
-	up_read(&sbi->quota_sem);
 	return ret;
 }