ext4: fix synchronization of quota files in journal=data mode

In journal=data mode, it is not enough to do write_inode_now as done in
vfs_quota_on() to write all data to their final location (which is
needed for quota_read to work correctly).  Calling journal_flush() does
its job.

Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 94a5272..cddf7f0 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3170,23 +3170,42 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
 
        if (!test_opt(sb, QUOTA))
                return -EINVAL;
-       /* Not journalling quota? */
-       if ((!EXT4_SB(sb)->s_qf_names[USRQUOTA] &&
-           !EXT4_SB(sb)->s_qf_names[GRPQUOTA]) || remount)
+       /* When remounting, no checks are needed and in fact, path is NULL */
+       if (remount)
                return vfs_quota_on(sb, type, format_id, path, remount);
+
        err = path_lookup(path, LOOKUP_FOLLOW, &nd);
        if (err)
                return err;
+
        /* Quotafile not on the same filesystem? */
        if (nd.path.mnt->mnt_sb != sb) {
                path_put(&nd.path);
                return -EXDEV;
        }
-       /* Quotafile not of fs root? */
-       if (nd.path.dentry->d_parent->d_inode != sb->s_root->d_inode)
-               printk(KERN_WARNING
-                       "EXT4-fs: Quota file not on filesystem root. "
-                       "Journalled quota will not work.\n");
+       /* Journaling quota? */
+       if (EXT4_SB(sb)->s_qf_names[type]) {
+               /* Quotafile not of fs root? */
+               if (nd.path.dentry->d_parent->d_inode != sb->s_root->d_inode)
+                       printk(KERN_WARNING
+                               "EXT4-fs: Quota file not on filesystem root. "
+                               "Journaled quota will not work.\n");
+       }
+
+       /*
+        * When we journal data on quota file, we have to flush journal to see
+        * all updates to the file when we bypass pagecache...
+        */
+       if (ext4_should_journal_data(nd.path.dentry->d_inode)) {
+               /*
+                * We don't need to lock updates but journal_flush() could
+                * otherwise be livelocked...
+                */
+               jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
+               jbd2_journal_flush(EXT4_SB(sb)->s_journal);
+               jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
+       }
+
        path_put(&nd.path);
        return vfs_quota_on(sb, type, format_id, path, remount);
 }