linux-kernel - Re: [PATCH 5/6] fsmount: do not use legacy MS

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Date:   Fri, 21 Sep 2018 17:28:21 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     David Howells <dhowells@...hat.com>
Cc:     Miklos Szeredi <mszeredi@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian@...uner.io>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] fsmount: do not use legacy MS_ flags

On Fri, Sep 21, 2018 at 5:07 PM, David Howells <dhowells@...hat.com> wrote:
> Miklos Szeredi <mszeredi@...hat.com> wrote:
>
>> What happens if we introduce new flags for fsmount(2) and are already out
>> of flags for mount(2)?  I see a big mess that way.
>>
>> So let's instead start a clean new set, to be used in the new API.
>
> If we must.  But let's not call them just M_* please.  Let's call them
> MOUNT_ATTR_* or something.

Oh well.

>> The MS_RELATIME flag was accepted but ignored.  Simply leave this out of
>> the new set, since "relatime" is the default.
>
> Can we make RELATIME, STRICTATIME and NOATIME an enum rather than individual
> flags?

Sure.

>
>         #define MOUNT_ATTR_RDONLY       0x01
>         #define MOUNT_ATTR_NOSUID       0x02
>         #define MOUNT_ATTR_NODEV        0x04
>         #define MOUNT_ATTR_NOEXEC       0x08
>         #define MOUNT_ATTR_RELATIME     0x00
>         #define MOUNT_ATTR_NOATIME      0x10
>         #define MOUNT_ATTR_STRICTATIME  0x20
>         #define MOUNT_ATTR_ATIME_MASK   0x30
>         #define MOUNT_ATTR_NODIRATIME   0x40
>
> We can also use these for a mount_setattr() syscall:
>
>         mount_setattr(int dfd, const char *path, unsigned int atflags,
>                       unsigned int attr_values,
>                       unsigned int attr_mask);
>
> where atflags can potentially include AT_RECURSIVE.

Indeed.  Also, shouldn't these include the propagation flags?

Thanks,
Miklos