quota: Add ->quota_{enable,disable} callbacks for VFS quotas

Add functions which translate ->quota_enable / ->quota_disable 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.

Also provide a vector for quotactl using these functions which can be
used by filesystems with quota files stored in hidden system files.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 91 insertions, 0 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 29eb9dc5728a..b47d0c17ea6f 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2385,6 +2385,86 @@ out:
 }
 EXPORT_SYMBOL(dquot_quota_on_mount);
 
+static int dquot_quota_enable(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_enforce_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_enforce_flag(type))
+                        dquot_disable(sb, type, DQUOT_LIMITS_ENABLED);
+        }
+        /* Error code translation for better compatibility with XFS */
+        if (ret == -EBUSY)
+                ret = -EEXIST;
+        return ret;
+}
+
+static int dquot_quota_disable(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_enforce_flag(type);
+        /* Nothing left? */
+        if (!flags)
+                return -EEXIST;
+        for (type = 0; type < MAXQUOTAS; type++) {
+                if (flags & qtype_enforce_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_enforce_flag(type))
+                        dquot_enable(dqopt->files[type], type,
+                                     dqopt->info[type].dqi_fmt_id,
+                                     DQUOT_LIMITS_ENABLED);
+        }
+        return ret;
+}
+
 static inline qsize_t qbtos(qsize_t blocks)
 {
         return blocks << QIF_DQBLKSIZE_BITS;
@@ -2614,6 +2694,17 @@ const struct quotactl_ops dquot_quotactl_ops = {
 };
 EXPORT_SYMBOL(dquot_quotactl_ops);
 
+const struct quotactl_ops dquot_quotactl_sysfile_ops = {
+        .quota_enable   = dquot_quota_enable,
+        .quota_disable  = dquot_quota_disable,
+        .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
+};
+EXPORT_SYMBOL(dquot_quotactl_sysfile_ops);
+
 static int do_proc_dqstats(struct ctl_table *table, int write,
                      void __user *buffer, size_t *lenp, loff_t *ppos)
 {