From: Peng Tao <bergwolf@gmail.com>
To: Alessio Balsini <balsini@android.com>
Cc: qxy <qxy65535@gmail.com>, Miklos Szeredi <miklos@szeredi.hu>,
Akilesh Kailash <akailash@google.com>,
Amir Goldstein <amir73il@gmail.com>,
Antonio SJ Musumeci <trapexit@spawn.link>,
David Anderson <dvander@google.com>,
Giuseppe Scrivano <gscrivan@redhat.com>,
Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk>,
Martijn Coenen <maco@android.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Lawrence <paullawrence@google.com>,
Stefano Duo <duostefano93@gmail.com>,
Zimuzo Ezeozue <zezeozue@google.com>, wuyan <wu-yan@tcl.com>,
fuse-devel@lists.sourceforge.net, kernel-team@android.com,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RESEND V12 2/8] fuse: 32-bit user space ioctl compat for fuse device
Date: Fri, 5 Feb 2021 17:54:05 +0800 [thread overview]
Message-ID: <CA+a=Yy7gfKbpgOd3+9HPGxvyU821p8yxkjz6cbOKJd_hN5Nekg@mail.gmail.com> (raw)
In-Reply-To: <YBLG+QlXqVB/bo/u@google.com>
On Thu, Jan 28, 2021 at 10:15 PM Alessio Balsini <balsini@android.com> wrote:
>
> Hi all,
>
> I'm more than happy to change the interface into something that is
> objectively better and accepted by everyone.
> I would really love to reach the point at which we have a "stable-ish"
> UAPI as soon as possible.
>
> I've been thinking about a few possible approaches to fix the issue, yet
> to preserve its flexibility. These are mentioned below.
>
>
> Solution 1: Size
>
> As mentioned in my previous email, one solution could be to introduce
> the "size" field to allow the structure to grow in the future.
>
> struct fuse_passthrough_out {
> uint32_t size; // Size of this data structure
> uint32_t fd;
> };
>
> The problem here is that we are making the promise that all the upcoming
> fields are going to be maintained forever and at the offsets they were
> originally defined.
>
>
> Solution 2: Version
>
> Another solution could be to s/size/version, where for every version of
> FUSE passthrough we reserve the right to modifying the fields over time,
> casting them to the right data structure according to the version.
>
>
> Solution 3: Type
>
> Using an enumerator to define the data structure content and purpose is
> the most flexible solution I can think of. This would for example allow
> us to substitute FUSE_DEV_IOC_PASSTHROUGH_OPEN with the generic
> FUSE_DEV_IOC_PASSTHROUGH and having a single ioctl for any eventually
> upcoming passthrough requests.
>
> enum fuse_passthrough_type {
> FUSE_PASSTHROUGH_OPEN
> };
>
> struct fuse_passthrough_out {
> uint32_t type; /* as defined by enum fuse_passthrough_type */
> union {
> uint32_t fd;
> };
> };
>
> This last is my favorite, as regardless the minimal logic required to
> detect the size and content of the struct (not required now as we only
> have a single option), it would also allow to do some kind of interface
> versioning (e.g., in case we want to implement
> FUSE_PASSTHROUGH_OPEN_V2).
>
Usually a new type of ioctl will be added in such cases. If we want to
stick to the same ioctl number, it might be easier to add a `flags`
field to differentiate compatible passthrough ioctls. So in future, if
a new interface is compatible with the existing one, we can use flags
to tell it. If it is not compatible, we still need to add a new ioctl.
wdyt?
struct fuse_passthrough_out {
uint32_t flags;
union {
uint32_t fd;
};
};
This somehow follows the "Flags as a system call API design pattern"
(https://lwn.net/Articles/585415/).
Just my two cents.
Cheers,
Tao
--
Into Sth. Rich & Strange
next prev parent reply other threads:[~2021-02-06 0:58 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 15:30 [PATCH RESEND V12 0/8] fuse: Add support for passthrough read/write Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 1/8] fs: Generic function to convert iocb to rw flags Alessio Balsini
2021-01-25 16:46 ` Alessio Balsini
2021-03-24 7:43 ` Rokudo Yan
2021-03-24 14:02 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 2/8] fuse: 32-bit user space ioctl compat for fuse device Alessio Balsini
[not found] ` <CAMAHBGzkfEd9-1u0iKXp65ReJQgUi_=4sMpmfkwEOaMp6Ux7pg@mail.gmail.com>
2021-01-27 13:40 ` Alessio Balsini
[not found] ` <CAMAHBGwpKW+30kNQ_Apt8A-FTmr94hBOzkT21cjEHHW+t7yUMQ@mail.gmail.com>
2021-01-28 14:15 ` Alessio Balsini
2021-02-05 9:54 ` Peng Tao [this message]
2021-03-16 18:57 ` Arnd Bergmann
2021-02-17 10:21 ` Miklos Szeredi
2021-03-01 12:26 ` Alessio Balsini
2021-03-16 18:53 ` Arnd Bergmann
2021-03-18 16:13 ` Alessio Balsini
2021-03-18 21:15 ` Arnd Bergmann
2021-03-19 15:21 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 3/8] fuse: Definitions and ioctl for passthrough Alessio Balsini
2021-02-17 13:41 ` Miklos Szeredi
2021-02-19 7:05 ` Peng Tao
2021-02-19 8:40 ` Miklos Szeredi
2021-03-01 17:05 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 4/8] fuse: Passthrough initialization and release Alessio Balsini
2021-02-17 13:52 ` Miklos Szeredi
2021-05-05 12:21 ` Amir Goldstein
2021-05-17 11:36 ` Alessio Balsini
2021-05-17 13:21 ` Amir Goldstein
2021-01-25 15:30 ` [PATCH RESEND V12 5/8] fuse: Introduce synchronous read and write for passthrough Alessio Balsini
2021-02-17 14:00 ` Miklos Szeredi
2021-01-25 15:30 ` [PATCH RESEND V12 6/8] fuse: Handle asynchronous read and write in passthrough Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 7/8] fuse: Use daemon creds in passthrough mode Alessio Balsini
2021-02-05 9:23 ` Peng Tao
2021-02-05 11:21 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 8/8] fuse: Introduce passthrough for mmap Alessio Balsini
2021-02-17 14:05 ` Miklos Szeredi
2021-04-01 11:24 ` Alessio Balsini
2021-11-18 18:31 ` [PATCH RESEND V12 0/8] fuse: Add support for passthrough read/write Amir Goldstein
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