quota: Split dquot_quota_sync() to writeback and cache flushing part

Split off part of dquot_quota_sync() which writes dquots into a quota file
to a separate function. In the next patch we will use the function from
filesystems and we do not want to abuse ->quota_sync quotactl callback more
than necessary.

Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 10cbe84..d679fc4 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -595,12 +595,14 @@
 }
 EXPORT_SYMBOL(dquot_scan_active);
 
-int dquot_quota_sync(struct super_block *sb, int type, int wait)
+/* Write all dquot structures to quota files */
+int dquot_writeback_dquots(struct super_block *sb, int type)
 {
 	struct list_head *dirty;
 	struct dquot *dquot;
 	struct quota_info *dqopt = sb_dqopt(sb);
 	int cnt;
+	int err, ret = 0;
 
 	mutex_lock(&dqopt->dqonoff_mutex);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
@@ -624,7 +626,9 @@
 			atomic_inc(&dquot->dq_count);
 			spin_unlock(&dq_list_lock);
 			dqstats_inc(DQST_LOOKUPS);
-			sb->dq_op->write_dquot(dquot);
+			err = sb->dq_op->write_dquot(dquot);
+			if (!ret && err)
+				err = ret;
 			dqput(dquot);
 			spin_lock(&dq_list_lock);
 		}
@@ -638,7 +642,21 @@
 	dqstats_inc(DQST_SYNCS);
 	mutex_unlock(&dqopt->dqonoff_mutex);
 
-	if (!wait || (dqopt->flags & DQUOT_QUOTA_SYS_FILE))
+	return ret;
+}
+EXPORT_SYMBOL(dquot_writeback_dquots);
+
+/* Write all dquot structures to disk and make them visible from userspace */
+int dquot_quota_sync(struct super_block *sb, int type)
+{
+	struct quota_info *dqopt = sb_dqopt(sb);
+	int cnt;
+	int ret;
+
+	ret = dquot_writeback_dquots(sb, type);
+	if (ret)
+		return ret;
+	if (dqopt->flags & DQUOT_QUOTA_SYS_FILE)
 		return 0;
 
 	/* This is not very clever (and fast) but currently I don't know about
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 9a39120..c659f92 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -47,7 +47,7 @@
 static void quota_sync_one(struct super_block *sb, void *arg)
 {
 	if (sb->s_qcop && sb->s_qcop->quota_sync)
-		sb->s_qcop->quota_sync(sb, *(int *)arg, 1);
+		sb->s_qcop->quota_sync(sb, *(int *)arg);
 }
 
 static int quota_sync_all(int type)
@@ -270,7 +270,7 @@
 	case Q_SYNC:
 		if (!sb->s_qcop->quota_sync)
 			return -ENOSYS;
-		return sb->s_qcop->quota_sync(sb, type, 1);
+		return sb->s_qcop->quota_sync(sb, type);
 	case Q_XQUOTAON:
 	case Q_XQUOTAOFF:
 	case Q_XQUOTARM: