[PATCH] quotactl(): sync all quotas

From: Jan Kara <jack@suse.cz>

  I'm resending a patch which implements quotactl(2) call for syncing
all devices. Particulary it allows the caller not to specify the device
for syncing and in that case quotas on all the devices are written.
The patch is rather trivial (mostly moving the code).

fs/dquot.c

@@ -345,50 +345,6 @@ static int vfs_quota_sync(struct super_block *sb, int type)
 	return 0;
 }
 
-static struct super_block *get_super_to_sync(int type)
-{
-	struct list_head *head;
-	int cnt, dirty;
-
-restart:
-	spin_lock(&sb_lock);
-	list_for_each(head, &super_blocks) {
-		struct super_block *sb = list_entry(head, struct super_block, s_list);
-
-		for (cnt = 0, dirty = 0; cnt < MAXQUOTAS; cnt++)
-			if ((type == cnt || type == -1) && sb_has_quota_enabled(sb, cnt)
-			    && info_any_dquot_dirty(&sb_dqopt(sb)->info[cnt]))
-				dirty = 1;
-		if (!dirty)
-			continue;
-		sb->s_count++;
-		spin_unlock(&sb_lock);
-		down_read(&sb->s_umount);
-		if (!sb->s_root) {
-			drop_super(sb);
-			goto restart;
-		}
-		return sb;
-	}
-	spin_unlock(&sb_lock);
-	return NULL;
-}
-
-void sync_dquots(struct super_block *sb, int type)
-{
-	if (sb) {
-		if (sb->s_qcop->quota_sync)
-			sb->s_qcop->quota_sync(sb, type);
-	}
-	else {
-		while ((sb = get_super_to_sync(type))) {
-			if (sb->s_qcop->quota_sync)
-				sb->s_qcop->quota_sync(sb, type);
-			drop_super(sb);
-		}
-	}
-}
-
 /* Free unused dquots from cache */
 static void prune_dqcache(int count)
 {

fs/quota.c

@@ -19,8 +19,10 @@ static int check_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t
 {
 	if (type >= MAXQUOTAS)
 		return -EINVAL;
+	if (!sb && cmd != Q_SYNC)
+		return -ENODEV;
 	/* Is operation supported? */
-	if (!sb->s_qcop)
+	if (sb && !sb->s_qcop)
 		return -ENOSYS;
 
 	switch (cmd) {
@@ -51,7 +53,7 @@ static int check_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t
 				return -ENOSYS;
 			break;
 		case Q_SYNC:
-			if (!sb->s_qcop->quota_sync)
+			if (sb && !sb->s_qcop->quota_sync)
 				return -ENOSYS;
 			break;
 		case Q_XQUOTAON:
@@ -102,6 +104,50 @@ static int check_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t
 	return security_quotactl (cmd, type, id, sb);
 }
 
+static struct super_block *get_super_to_sync(int type)
+{
+	struct list_head *head;
+	int cnt, dirty;
+
+restart:
+	spin_lock(&sb_lock);
+	list_for_each(head, &super_blocks) {
+		struct super_block *sb = list_entry(head, struct super_block, s_list);
+
+		for (cnt = 0, dirty = 0; cnt < MAXQUOTAS; cnt++)
+			if ((type == cnt || type == -1) && sb_has_quota_enabled(sb, cnt)
+			    && info_any_dquot_dirty(&sb_dqopt(sb)->info[cnt]))
+				dirty = 1;
+		if (!dirty)
+			continue;
+		sb->s_count++;
+		spin_unlock(&sb_lock);
+		down_read(&sb->s_umount);
+		if (!sb->s_root) {
+			drop_super(sb);
+			goto restart;
+		}
+		return sb;
+	}
+	spin_unlock(&sb_lock);
+	return NULL;
+}
+
+void sync_dquots(struct super_block *sb, int type)
+{
+	if (sb) {
+		if (sb->s_qcop->quota_sync)
+			sb->s_qcop->quota_sync(sb, type);
+	}
+	else {
+		while ((sb = get_super_to_sync(type))) {
+			if (sb->s_qcop->quota_sync)
+				sb->s_qcop->quota_sync(sb, type);
+			drop_super(sb);
+		}
+	}
+}
+
 /* Copy parameters and call proper function */
 static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id, caddr_t addr)
 {
@@ -167,7 +213,8 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id, cadd
 			return sb->s_qcop->set_dqblk(sb, type, id, &idq);
 		}
 		case Q_SYNC:
-			return sb->s_qcop->quota_sync(sb, type);
+			sync_dquots(sb, type);
+			return 0;
 
 		case Q_XQUOTAON:
 		case Q_XQUOTAOFF:
@@ -222,11 +269,12 @@ asmlinkage long sys_quotactl(unsigned int cmd, const char *special, qid_t id, ca
 	struct super_block *sb = NULL;
 	struct block_device *bdev;
 	char *tmp;
-	int ret = -ENODEV;
+	int ret;
 
 	cmds = cmd >> SUBCMDSHIFT;
 	type = cmd & SUBCMDMASK;
 
+	if (cmds != Q_SYNC || special) {
 		tmp = getname(special);
 		if (IS_ERR(tmp))
 			return PTR_ERR(tmp);
@@ -236,13 +284,15 @@ asmlinkage long sys_quotactl(unsigned int cmd, const char *special, qid_t id, ca
 			return PTR_ERR(bdev);
 		sb = get_super(bdev);
 		bdput(bdev);
+		if (!sb)
+			return -ENODEV;
+	}
 
-	if (sb) {
 	ret = check_quotactl_valid(sb, type, cmds, id);
 	if (ret >= 0)
 		ret = do_quotactl(sb, type, cmds, id, addr);
+	if (sb)
 		drop_super(sb);
-	}
 
 	return ret;
 }