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>

1 files changed, 27 insertions, 8 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 94a527261cae..cddf7f0e0fda 100644
--- 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);
 }