Re: [PATCH 3/4] Adds project quota support for ext4

On Thu, Sep 25, 2014 at 1:31 AM, Jan Kara [off-list ref] wrote:

On Wed 24-09-14 22:04:29, Li Xi wrote:

quoted

This patch adds mount options for enabling/disabling project quota
accounting and enforcement. A new specific inode is also used for
project quota accounting.

  The patch looks mostly fine. A few smaller things below.

...

quoted

@@ -1433,6 +1437,8 @@ static const struct mount_opts {
                                                      MOPT_SET | MOPT_Q},
      {Opt_grpquota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_GRPQUOTA,
                                                      MOPT_SET | MOPT_Q},
+     {Opt_prjquota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_PRJQUOTA,
+                                                     MOPT_SET | MOPT_Q},
      {Opt_noquota, (EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA |
                     EXT4_MOUNT_GRPQUOTA), MOPT_CLEAR | MOPT_Q},

  I think you missed to add EXT4_MOUNT_PRJQUOTA to Opt_noquota...

...

quoted

@@ -2833,6 +2855,13 @@ static int ext4_feature_set_ok(struct super_block *sb, int readonly)
                       "without CONFIG_QUOTA");
              return 0;
      }
+     if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_PROJECT) &&
+         !readonly) {
+             ext4_msg(sb, KERN_ERR,
+                      "Filesystem with project quota feature cannot be"
+                      "mounted RDWR without CONFIG_QUOTA");
+             return 0;
+     }

  Hum, I don't think this is right. EXT4_FEATURE_RO_COMPAT_PROJECT is about
maintaining project IDs not about quota. So it seems perfectly OK to have
EXT4_FEATURE_RO_COMPAT_PROJECT without CONFIG_QUOTA.

Ah, I see. This might be my main misunderstanding. I thought it is
about maintaining
both project IDs and quota. And I misunderstood so that I removed all
EXT4_FEATURE_RO_COMPAT_PROJECT checking when set/get project ID.
If we only use EXT4_FEATURE_RO_COMPAT_PROJECT to protect imcompatibility
of project ID, what about the change of struct ext4_super_block? I am
still confused.
Please advise.

Regards,
Li Xi