[v2,2/2] ext4: print quota journalling mode on (re-)mount

Right now, it is hard to understand what quota journalling type is enabled:
you need to be quite familiar with kernel code and trace it or really
understand what different combinations of fs flags/mount options lead to.

This patch adds printing of current quota jounalling mode on each
mount/remount, thus making it easier to check it at a glance/in autotests.
The semantics is similar to ext4 data journalling modes:

* journalled - quota accounting and journaling are enabled
* writeback  - quota accounting is enabled, but journalling is disabled
* none       - quota accounting is disabled
* disabled   - kernel compiled without CONFIG_QUOTA feature

Signed-off-by: Roman Anufriev <dotdot@yandex-team.ru>
---
Changes in v2:
  - Print quota journalling mode instead of exporting it via sysfs.

 fs/ext4/super.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

Hi Roman,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on ext4/dev]
[also build test ERROR on v5.9 next-20201016]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Roman-Anufriev/ext4-add-helpers-for-checking-whether-quota-can-be-enabled-is-journalled/20201018-100410
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
config: i386-randconfig-m021-20201018 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/9ee2e9dad32135b665f733b714c75ff22731bbcd
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Roman-Anufriev/ext4-add-helpers-for-checking-whether-quota-can-be-enabled-is-journalled/20201018-100410
        git checkout 9ee2e9dad32135b665f733b714c75ff22731bbcd
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/ext4/super.c: In function 'ext4_quota_mode':
>> fs/ext4/super.c:3999:19: error: expected ';' before '}' token
    3999 |  return "disabled"
         |                   ^
         |                   ;
    4000 | #endif
    4001 | }
         | ~                  
   fs/ext4/super.c: In function 'ext4_remount':
   fs/ext4/super.c:5738:6: warning: variable 'enable_quota' set but not used [-Wunused-but-set-variable]
    5738 |  int enable_quota = 0;
         |      ^~~~~~~~~~~~

vim +3999 fs/ext4/super.c

  3987	
  3988	static const char *ext4_quota_mode(struct super_block *sb)
  3989	{
  3990	#ifdef CONFIG_QUOTA
  3991		if (!ext4_quota_capable(sb))
  3992			return "none";
  3993	
  3994		if (ext4_is_quota_journalled(sb))
  3995			return "journalled";
  3996		else
  3997			return "writeback";
  3998	#else
> 3999		return "disabled"
  4000	#endif
  4001	}
  4002	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

On Sun, 18 Oct 2020, kernel test robot wrote:

> Hi Roman,
>
> Thank you for the patch! Yet something to improve:
>
> [auto build test ERROR on ext4/dev]
> [also build test ERROR on v5.9 next-20201016]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
>
> url:    https://github.com/0day-ci/linux/commits/Roman-Anufriev/ext4-add-helpers-for-checking-whether-quota-can-be-enabled-is-journalled/20201018-100410
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
> config: i386-randconfig-m021-20201018 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
> reproduce (this is a W=1 build):
>        # https://github.com/0day-ci/linux/commit/9ee2e9dad32135b665f733b714c75ff22731bbcd
>        git remote add linux-review https://github.com/0day-ci/linux
>        git fetch --no-tags linux-review Roman-Anufriev/ext4-add-helpers-for-checking-whether-quota-can-be-enabled-is-journalled/20201018-100410
>        git checkout 9ee2e9dad32135b665f733b714c75ff22731bbcd
>        # save the attached .config to linux build tree
>        make W=1 ARCH=i386
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>   fs/ext4/super.c: In function 'ext4_quota_mode':
>>> fs/ext4/super.c:3999:19: error: expected ';' before '}' token
>    3999 |  return "disabled"
>         |                   ^
>         |                   ;
>    4000 | #endif
>    4001 | }
>         | ~
>   fs/ext4/super.c: In function 'ext4_remount':
>   fs/ext4/super.c:5738:6: warning: variable 'enable_quota' set but not used [-Wunused-but-set-variable]
>    5738 |  int enable_quota = 0;
>         |      ^~~~~~~~~~~~
>
> vim +3999 fs/ext4/super.c
>
>  3987
>  3988	static const char *ext4_quota_mode(struct super_block *sb)
>  3989	{
>  3990	#ifdef CONFIG_QUOTA
>  3991		if (!ext4_quota_capable(sb))
>  3992			return "none";
>  3993
>  3994		if (ext4_is_quota_journalled(sb))
>  3995			return "journalled";
>  3996		else
>  3997			return "writeback";
>  3998	#else
>> 3999		return "disabled"
>  4000	#endif
>  4001	}
>  4002
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Fixed missing semicolon in v3:
https://lore.kernel.org/linux-ext4/1603099162-25028-1-git-send-email-dotdot@yandex-team.ru/

 								Roman

On Sun 18-10-20 05:02:27, Roman Anufriev wrote:
> Right now, it is hard to understand what quota journalling type is enabled:
> you need to be quite familiar with kernel code and trace it or really
> understand what different combinations of fs flags/mount options lead to.
> 
> This patch adds printing of current quota jounalling mode on each
> mount/remount, thus making it easier to check it at a glance/in autotests.
> The semantics is similar to ext4 data journalling modes:
> 
> * journalled - quota accounting and journaling are enabled
> * writeback  - quota accounting is enabled, but journalling is disabled

The above two descriptions are still somewhat misleading - in fact we don't
know whether accounting is enabled or not. Just *if* it is enabled, quota
will be journalled / non-journalled. So I'd probably describe it like:
 * journalled - quota configured, journalling will be enabled
 * writeback - quota configured, journalling will be disabled

We've talked with Ted on last ext4 conf call and we agreed that it's
probably time to deprecate old style quotas in external quota files and
transition everybody to using quotas with quota feature. That way things
will get simpler again. But before we can disable that functionality, it
will take a few years of deprecation warnings etc. so that's not directly
related to your patch here. JFYI.

								Honza

> * none       - quota accounting is disabled
> * disabled   - kernel compiled without CONFIG_QUOTA feature
> 
> Signed-off-by: Roman Anufriev <dotdot@yandex-team.ru>
> ---
> Changes in v2:
>   - Print quota journalling mode instead of exporting it via sysfs.
> 
>  fs/ext4/super.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index a988cf3..09b5645 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3985,6 +3985,21 @@ static void ext4_set_resv_clusters(struct super_block *sb)
>  	atomic64_set(&sbi->s_resv_clusters, resv_clusters);
>  }
>  
> +static const char *ext4_quota_mode(struct super_block *sb)
> +{
> +#ifdef CONFIG_QUOTA
> +	if (!ext4_quota_capable(sb))
> +		return "none";
> +
> +	if (ext4_is_quota_journalled(sb))
> +		return "journalled";
> +	else
> +		return "writeback";
> +#else
> +	return "disabled"
> +#endif
> +}
> +
>  static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  {
>  	struct dax_device *dax_dev = fs_dax_get_by_bdev(sb->s_bdev);
> @@ -5039,10 +5054,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  
>  	if (___ratelimit(&ext4_mount_msg_ratelimit, "EXT4-fs mount"))
>  		ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
> -			 "Opts: %.*s%s%s", descr,
> +			 "Opts: %.*s%s%s. Quota mode: %s.", descr,
>  			 (int) sizeof(sbi->s_es->s_mount_opts),
>  			 sbi->s_es->s_mount_opts,
> -			 *sbi->s_es->s_mount_opts ? "; " : "", orig_data);
> +			 *sbi->s_es->s_mount_opts ? "; " : "", orig_data,
> +			 ext4_quota_mode(sb));
>  
>  	if (es->s_error_count)
>  		mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
> @@ -5979,7 +5995,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>  	 */
>  	*flags = (*flags & ~vfs_flags) | (sb->s_flags & vfs_flags);
>  
> -	ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s", orig_data);
> +	ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s. Quota mode: %s.",
> +		 orig_data, ext4_quota_mode(sb));
>  	kfree(orig_data);
>  	return 0;
>  
> -- 
> 2.7.4
>

On Mon, 19 Oct 2020, Jan Kara wrote:

> On Sun 18-10-20 05:02:27, Roman Anufriev wrote:
>> Right now, it is hard to understand what quota journalling type is enabled:
>> you need to be quite familiar with kernel code and trace it or really
>> understand what different combinations of fs flags/mount options lead to.
>>
>> This patch adds printing of current quota jounalling mode on each
>> mount/remount, thus making it easier to check it at a glance/in autotests.
>> The semantics is similar to ext4 data journalling modes:
>>
>> * journalled - quota accounting and journaling are enabled
>> * writeback  - quota accounting is enabled, but journalling is disabled
>
> The above two descriptions are still somewhat misleading - in fact we don't
> know whether accounting is enabled or not. Just *if* it is enabled, quota
> will be journalled / non-journalled. So I'd probably describe it like:
> * journalled - quota configured, journalling will be enabled
> * writeback - quota configured, journalling will be disabled

Yeah, you are right, I'll fix this in v4.

> We've talked with Ted on last ext4 conf call and we agreed that it's
> probably time to deprecate old style quotas in external quota files and
> transition everybody to using quotas with quota feature. That way things
> will get simpler again. But before we can disable that functionality, it
> will take a few years of deprecation warnings etc. so that's not directly
> related to your patch here. JFYI.

It will be great!

 								Roman