Messages in this thread | | | Date | Thu, 28 Jan 2021 14:15:21 +0000 | From | Alessio Balsini <> | Subject | Re: [PATCH RESEND V12 2/8] fuse: 32-bit user space ioctl compat for fuse device |
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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).
What do you think?
Thanks, Alessio
P.S. Sorry if you received a duplicate email. I first sent this in reply to an email without realizing it was a private message.
On Thu, Jan 28, 2021 at 11:01:59AM +0800, qxy wrote: > Hi Alessio, > > I have received a failure from the Mail Delivery System for times and feel > really sorry if you have already received the duplicate message... > > Thank you for your reply. > I think it's wonderful to remove *vec from the data structure fields since > we consider that it is not a good idea to use pointer when there is a need > for cross-platform. > Do you have a plan to modify the kernel fuse_passthrough_out data structure > the same way as you mentioned? > > Thanks! > qixiaoyu
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