quota: Introduce writeout_quota_sb() (version 4)

Introduce this function which just writes all the quota structures but
avoids all the syncing and cache pruning work to expose quota structures
to userspace. Use this function from __sync_filesystem when wait == 0.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 14 insertions, 1 deletions

diff --git a/fs/sync.c b/fs/sync.c
index d90ab77..4487b55 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -27,7 +27,11 @@
  */
 static int __sync_filesystem(struct super_block *sb, int wait)
 {
-	sync_quota_sb(sb, -1);
+	/* Avoid doing twice syncing and cache pruning for quota sync */
+	if (!wait)
+		writeout_quota_sb(sb, -1);
+	else
+		sync_quota_sb(sb, -1);
 	sync_inodes_sb(sb, wait);
 	lock_super(sb);
 	if (sb->s_dirt && sb->s_op->write_super)
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 047310f..7bc4575 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -21,6 +21,11 @@ static inline struct quota_info *sb_dqopt(struct super_block *sb)
  * declaration of quota_function calls in kernel.
  */
 void sync_quota_sb(struct super_block *sb, int type);
+static inline void writeout_quota_sb(struct super_block *sb, int type)
+{
+	if (sb->s_qcop->quota_sync)
+		sb->s_qcop->quota_sync(sb, type);
+}
 
 int dquot_initialize(struct inode *inode, int type);
 int dquot_drop(struct inode *inode);
@@ -333,6 +338,10 @@ static inline void sync_quota_sb(struct super_block *sb, int type)
 {
 }
 
+static inline void writeout_quota_sb(struct super_block *sb, int type)
+{
+}
+
 static inline int vfs_dq_off(struct super_block *sb, int remount)
 {
 	return 0;