linux-kernel - Re: [RFC][PATCH 00/23] VFS: Introduce superblock configuration context [ver #4]

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Message-ID: <CAOssrKewzKn-5=b3n84mP=8EROCP22thcizggQfueh+CqDHKDg@mail.gmail.com>
Date:   Wed, 31 May 2017 09:51:02 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-nfs@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 00/23] VFS: Introduce superblock configuration
 context [ver #4]

On Tue, May 30, 2017 at 5:36 PM, David Howells <dhowells@...hat.com> wrote:
> Al Viro <viro@...IV.linux.org.uk> wrote:
>
>> Random notes:
>>       * "sb_config" looks rather odd in the current variant; mount_context,
>> perhaps?  Or fs_context, for that matter...  Anyway, that's trivial.
>
> You can argue that one with Miklós.  He argued against mount_context as I had
> it originally.  His point is that the same struct may be used when
> reconfiguring an sb - which isn't exactly a mount operation (even though we do
> it that day today with remount).

I'm fine with fs_context, just leave "mount" out of this.  Mounting is
the act of attaching the root dentry to the mountpoint. fs_context is
used for obtaining the root, but not for mounting itself, hence
mount_context is misleading IMO.

>>       * what the hell is ms_flags thing doing in __vfs_new_sb_config()?
>> It's a really vile mix of unrelated flags and operations we had in existing
>> mount(2) ABI.  With MS_KERNMOUNT thrown into that loo^Wmix.  Sure, we need
>> to parse the garbage fed to mount(2).  And we need to pass that garbage to
>> "legacy" types as well, but let's not inflict it upon the new mechanisms.
>
> I know, but we might get it from mount(2).  I can tamp down the flag mask and
> translate it from MS_*, but the MS_* flags are also stored in the superblock
> (->s_flags).

Good cleanup would be to just introduce a new set of flags for s_flags
and leave MS_* usage solely for the legacy mount(2) interface.

Thanks,
Miklos