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From: Jens Axboe <axboe@kernel.dk>
To: Stefan Metzmacher <metze@samba.org>, io-uring@vger.kernel.org
Subject: Re: [PATCHSET 0/4] Allow relative lookups
Date: Sat, 8 Feb 2020 13:05:15 -0700
Message-ID: <266cdea9-5a63-adab-a441-d3f1c4cb23d1@kernel.dk> (raw)
In-Reply-To: <1f8f18a5-f37a-c11b-3e72-716de4c580f7@samba.org>

On 2/7/20 3:56 PM, Stefan Metzmacher wrote:
> Hi Jens,
> 
>>> Am 07.02.20 um 16:50 schrieb Jens Axboe:
>>>> Due to an oversight on my part, AT_FDCWD lookups only work when the
>>>> lookup can be done inline, not async. This patchset rectifies that,
>>>> aiming for 5.6 for this one as it would be a shame to have openat etc
>>>> without that.
>>>>
>>>> Just 3 small simple patches - grab the task ->fs, add io-wq suppor for
>>>> passing it in and setting it, and finally add a ->needs_fs to the opcode
>>>> table list of requirements for openat/openat2/statx.
>>>>
>>>> Last patch just ensures we allow AT_FDCWD.
>>>
>>> Thanks! But IOSQE_FIXED_FILE is still not supported and not rejected at
>>> the same time, correct?
>>
>> That's in a separate patch:
>>
>> https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-5.6&id=5e159663813f0b7837342426cfb68185b6609359
> 
> Do we handle the error path correct?
> As far as I can see io_req_set_file() is called before
> io_{statx,openat,openat2}_prep() and req->file is already filled.
> Maybe a generic way would be better using io_op_defs[op].allow_fixed_file.

Worst case, as far as I can tell, is that we'll think it's a valid
descriptor (because the both the fixed index and fd are valid) and we'll
still error in the prep. Only concern would be that maybe we should make
this an -EBADF return, which would be 100% consistent between them (and
with other cases). I'll make that change.

> In the long run we may want to add support for openat2 with
> IOSQE_FIXED_FILE, then Samba could register the share root directory as
> fixed file and it could be used for all openat2 calls.
> But for now it's fine to just reject it...

It's not impossible to support, it's just that it requires changes
outside of io_uring to do so. So for now it'll just not be possible, I'm
afraid.

-- 
Jens Axboe


      parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-07 15:50 Jens Axboe
2020-02-07 15:50 ` [PATCH 1/4] io_uring: grab owning task fs_struct Jens Axboe
2020-02-07 15:50 ` [PATCH 2/4] io-wq: add support for inheriting ->fs Jens Axboe
2020-02-07 15:50 ` [PATCH 3/4] io_uring: add ->needs_fs to the opcode requirements table Jens Axboe
2020-02-07 15:50 ` [PATCH 4/4] io_uring: allow AT_FDCWD for non-file openat/openat2/statx Jens Axboe
2020-02-07 21:56 ` [PATCHSET 0/4] Allow relative lookups Stefan Metzmacher
2020-02-07 22:47   ` Jens Axboe
2020-02-07 22:56     ` Stefan Metzmacher
2020-02-07 23:07       ` Stefan Metzmacher
2020-02-08 20:05       ` Jens Axboe [this message]

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