[PATCH 06/11] quota: Add ->sysquota_{on,off} callbacks for VFS quotas

[Jan Kara <jack@suse.cz>]

Add functions which translate ->sysquota_on / ->sysquota_off calls into
appropriate changes in VFS quota. This will enable filesystems
supporting VFS quota files in system inodes to be controlled via
Q_XQUOTA[ON|OFF] quotactls for better userspace compatibility.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/quota/dquot.c         | 82 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/quotaops.h |  2 ++
 2 files changed, 84 insertions(+)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 6b4527216a7f..b7359c9da61e 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2380,6 +2380,88 @@ out:
 }
 EXPORT_SYMBOL(dquot_quota_on_mount);
 
+int dquot_sysquota_on(struct super_block *sb, unsigned int flags)
+{
+	int ret;
+	int type;
+	struct quota_info *dqopt = sb_dqopt(sb);
+
+	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE))
+		return -ENOSYS;
+	/* Accounting cannot be turned on while fs is mounted */
+	flags &= ~(FS_QUOTA_UDQ_ACCT | FS_QUOTA_GDQ_ACCT | FS_QUOTA_PDQ_ACCT);
+	if (!flags)
+		return -EINVAL;
+	for (type = 0; type < MAXQUOTAS; type++) {
+		if (!(flags & qtype_limit_flag(type)))
+			continue;
+		/* Can't enforce without accounting */
+		if (!sb_has_quota_usage_enabled(sb, type))
+			return -EINVAL;
+		ret = dquot_enable(dqopt->files[type], type,
+				   dqopt->info[type].dqi_fmt_id,
+				   DQUOT_LIMITS_ENABLED);
+		if (ret < 0)
+			goto out_err;
+	}
+	return 0;
+out_err:
+	/* Backout enforcement enablement we already did */
+	for (type--; type >= 0; type--)  {
+		if (flags & qtype_limit_flag(type))
+			dquot_disable(sb, type, DQUOT_LIMITS_ENABLED);
+	}
+	/* Error code translation for better compatibility with XFS */
+	if (ret == -EBUSY)
+		ret = -EEXIST;
+	return ret;
+}
+EXPORT_SYMBOL(dquot_sysquota_on);
+
+int dquot_sysquota_off(struct super_block *sb, unsigned int flags)
+{
+	int ret;
+	int type;
+	struct quota_info *dqopt = sb_dqopt(sb);
+
+	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE))
+		return -ENOSYS;
+	/*
+	 * We don't support turning off accounting via quotactl. In principle
+	 * quota infrastructure can do this but filesystems don't expect
+	 * userspace to be able to do it.
+	 */
+	if (flags &
+		  (FS_QUOTA_UDQ_ACCT | FS_QUOTA_GDQ_ACCT | FS_QUOTA_PDQ_ACCT))
+		return -EOPNOTSUPP;
+
+	/* Filter out limits not enabled */
+	for (type = 0; type < MAXQUOTAS; type++)
+		if (!sb_has_quota_limits_enabled(sb, type))
+			flags &= ~qtype_limit_flag(type);
+	/* Nothing left? */
+	if (!flags)
+		return -EEXIST;
+	for (type = 0; type < MAXQUOTAS; type++) {
+		if (flags & qtype_limit_flag(type)) {
+			ret = dquot_disable(sb, type, DQUOT_LIMITS_ENABLED);
+			if (ret < 0)
+				goto out_err;
+		}
+	}
+	return 0;
+out_err:
+	/* Backout enforcement disabling we already did */
+	for (type--; type >= 0; type--)  {
+		if (flags & qtype_limit_flag(type))
+			dquot_enable(dqopt->files[type], type,
+				     dqopt->info[type].dqi_fmt_id,
+				     DQUOT_LIMITS_ENABLED);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(dquot_sysquota_off);
+
 static inline qsize_t qbtos(qsize_t blocks)
 {
 	return blocks << QIF_DQBLKSIZE_BITS;
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 5947a9e54862..6f5dc7e397a7 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -93,6 +93,8 @@ int dquot_quota_on(struct super_block *sb, int type, int format_id,
 int dquot_quota_on_mount(struct super_block *sb, char *qf_name,
  	int format_id, int type);
 int dquot_quota_off(struct super_block *sb, int type);
+int dquot_sysquota_on(struct super_block *sb, unsigned int flags);
+int dquot_sysquota_off(struct super_block *sb, unsigned int flags);
 int dquot_writeback_dquots(struct super_block *sb, int type);
 int dquot_quota_sync(struct super_block *sb, int type);
 int dquot_get_dqinfo(struct super_block *sb, int type, struct if_dqinfo *ii);
-- 
1.8.1.4