linux-ext4 - Re: Kernel does not respect tune2fs -E mount

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Message-ID: <CAJZVDJDgz=QTARjPXDqh8YuFOiS6nO_BdTzNsb2hr5apPmLk5w@mail.gmail.com>
Date:   Tue, 23 Aug 2016 13:01:53 -0300
From:   Marcos Mello <marcosfrm@...il.com>
To:     tytso@....edu
Cc:     linux-ext4@...r.kernel.org
Subject: Re: Kernel does not respect tune2fs -E mount_opts=foo

2016-08-23 12:48 GMT-03:00  <tytso@....edu>:
> The problem you are running into is not something we can fix,
> unfortunately, or at least not in a full and general way.  The problem
> is that there are certain mount options which are parsed by the mount
> command (in userspace) and then translated to a mount flag, which is
> then passed to the mount command as a bitmask, and which is
> interpreted by the VFS layer before calling the file system.
>
> The mount options field in the superblock is parsed by the ext4 file
> system along with options that were not parsed by the mount binary,
> passed to the VFS, which then passed it to ext4 file system driver.
>
> In theory, we could interpret relatime in ext4 and replicate its
> effects.  For relatime, this is trivial to do.  There may be other
> mount options which are interepted by the mount userspace program, and
> implemented in the VFS, where this would be much less easy to do.
>
>> Other options like noacl, nouser_xattr, are ignored too. This
>> filesystem is not listed in fstab.
>
> This is exactly the same issue.
>

Thanks for the explanation. A hint about this limitation in tune2fs
man page would help.

Marcos
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