ext4: Use generic helpers for quotaon and quotaoff

Ext4 can just use the generic helpers provided by quota code for turning
quotas on and off when quota files are stored as system inodes. The only
difference is the feature test in ext4_quota_on_sysfile() but the same
is achieved in dquot_quota_enable() by checking whether usage tracking
for the corresponding quota type is enabled (which can happen only if
quota feature is set).
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext4/super.c

@@ -1046,10 +1046,7 @@ static int ext4_mark_dquot_dirty(struct dquot *dquot);
 static int ext4_write_info(struct super_block *sb, int type);
 static int ext4_quota_on(struct super_block *sb, int type, int format_id,
 			 struct path *path);
-static int ext4_quota_on_sysfile(struct super_block *sb, int type,
-				 int format_id);
 static int ext4_quota_off(struct super_block *sb, int type);
-static int ext4_quota_off_sysfile(struct super_block *sb, int type);
 static int ext4_quota_on_mount(struct super_block *sb, int type);
 static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data,
 			       size_t len, loff_t off);
@@ -1084,16 +1081,6 @@ static const struct quotactl_ops ext4_qctl_operations = {
 	.get_dqblk	= dquot_get_dqblk,
 	.set_dqblk	= dquot_set_dqblk
 };
-
-static const struct quotactl_ops ext4_qctl_sysfile_operations = {
-	.quota_on_meta	= ext4_quota_on_sysfile,
-	.quota_off	= ext4_quota_off_sysfile,
-	.quota_sync	= dquot_quota_sync,
-	.get_info	= dquot_get_dqinfo,
-	.set_info	= dquot_set_dqinfo,
-	.get_dqblk	= dquot_get_dqblk,
-	.set_dqblk	= dquot_set_dqblk
-};
 #endif
 
 static const struct super_operations ext4_sops = {
@@ -3935,7 +3922,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 #ifdef CONFIG_QUOTA
 	sb->dq_op = &ext4_quota_operations;
 	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA))
-		sb->s_qcop = &ext4_qctl_sysfile_operations;
+		sb->s_qcop = &dquot_quotactl_sysfile_ops;
 	else
 		sb->s_qcop = &ext4_qctl_operations;
 	sb->s_quota_types = QTYPE_MASK_USR | QTYPE_MASK_GRP;
@@ -5288,21 +5275,6 @@ static int ext4_enable_quotas(struct super_block *sb)
 	return 0;
 }
 
-/*
- * quota_on function that is used when QUOTA feature is set.
- */
-static int ext4_quota_on_sysfile(struct super_block *sb, int type,
-				 int format_id)
-{
-	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA))
-		return -EINVAL;
-
-	/*
-	 * USAGE was enabled at mount time. Only need to enable LIMITS now.
-	 */
-	return ext4_quota_enable(sb, type, format_id, DQUOT_LIMITS_ENABLED);
-}
-
 static int ext4_quota_off(struct super_block *sb, int type)
 {
 	struct inode *inode = sb_dqopt(sb)->files[type];
@@ -5329,18 +5301,6 @@ static int ext4_quota_off(struct super_block *sb, int type)
 	return dquot_quota_off(sb, type);
 }
 
-/*
- * quota_off function that is used when QUOTA feature is set.
- */
-static int ext4_quota_off_sysfile(struct super_block *sb, int type)
-{
-	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA))
-		return -EINVAL;
-
-	/* Disable only the limits. */
-	return dquot_disable(sb, type, DQUOT_LIMITS_ENABLED);
-}
-
 /* Read data from quotafile - avoid pagecache and such because we cannot afford
  * acquiring the locks... As quota files are never truncated and quota code
  * itself serializes the operations (and no one else should touch the files)