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([2620:10d:c092:600::1:429a]) by smtp.gmail.com with ESMTPSA id g38-20020a056402322600b0056b8cc4d6a7sm47915eda.43.2024.03.18.06.38.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Mar 2024 06:38:59 -0700 (PDT) Message-ID: <2095ac3e-5e5f-4ea2-a906-a924a25c121a@gmail.com> Date: Mon, 18 Mar 2024 13:37:23 +0000 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/14] ublk: don't hard code IO_URING_F_UNLOCKED Content-Language: en-US From: Pavel Begunkov To: Ming Lei Cc: io-uring@vger.kernel.org, linux-block@vger.kernel.org, Jens Axboe , Kanchan Joshi References: <61b29658-e6a9-449f-a850-1881af1ecbee@gmail.com> In-Reply-To: <61b29658-e6a9-449f-a850-1881af1ecbee@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 3/18/24 12:52, Pavel Begunkov wrote: > On 3/18/24 08:16, Ming Lei wrote: >> On Mon, Mar 18, 2024 at 12:41:50AM +0000, Pavel Begunkov wrote: >>> uring_cmd implementations should not try to guess issue_flags, just use >>> a newly added io_uring_cmd_complete(). We're loosing an optimisation in >>> the cancellation path in ublk_uring_cmd_cancel_fn(), but the assumption >>> is that we don't care that much about it. >>> >>> Signed-off-by: Pavel Begunkov >>> Link: https://lore.kernel.org/r/2f7bc9fbc98b11412d10b8fd88e58e35614e3147.1710514702.git.asml.silence@gmail.com >>> Signed-off-by: Jens Axboe >>> --- >>>   drivers/block/ublk_drv.c | 18 ++++++++---------- >>>   1 file changed, 8 insertions(+), 10 deletions(-) >>> >>> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c >>> index bea3d5cf8a83..97dceecadab2 100644 >>> --- a/drivers/block/ublk_drv.c >>> +++ b/drivers/block/ublk_drv.c >>> @@ -1417,8 +1417,7 @@ static bool ublk_abort_requests(struct ublk_device *ub, struct ublk_queue *ubq) >>>       return true; >>>   } >>> -static void ublk_cancel_cmd(struct ublk_queue *ubq, struct ublk_io *io, >>> -        unsigned int issue_flags) >>> +static void ublk_cancel_cmd(struct ublk_queue *ubq, struct ublk_io *io) >>>   { >>>       bool done; >>> @@ -1432,15 +1431,14 @@ static void ublk_cancel_cmd(struct ublk_queue *ubq, struct ublk_io *io, >>>       spin_unlock(&ubq->cancel_lock); >>>       if (!done) >>> -        io_uring_cmd_done(io->cmd, UBLK_IO_RES_ABORT, 0, issue_flags); >>> +        io_uring_cmd_complete(io->cmd, UBLK_IO_RES_ABORT, 0); >>>   } >>>   /* >>>    * The ublk char device won't be closed when calling cancel fn, so both >>>    * ublk device and queue are guaranteed to be live >>>    */ >>> -static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd, >>> -        unsigned int issue_flags) >>> +static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd) >>>   { >>>       struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd); >>>       struct ublk_queue *ubq = pdu->ubq; >>> @@ -1464,7 +1462,7 @@ static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd, >>>       io = &ubq->ios[pdu->tag]; >>>       WARN_ON_ONCE(io->cmd != cmd); >>> -    ublk_cancel_cmd(ubq, io, issue_flags); >>> +    ublk_cancel_cmd(ubq, io); >> >> .cancel_fn is always called with .uring_lock held, so this 'issue_flags' can't >> be removed, otherwise double task run is caused because .cancel_fn >> can be called multiple times if the request stays in ctx->cancelable_uring_cmd. > > I see, that's exactly why I was asking whether it can be deferred > to tw. Let me see if I can get by without that patch, but honestly > it's a horrible abuse of the ring state. Any ideas how that can be > cleaned up? I assume io_uring_try_cancel_uring_cmd() can run in parallel with completions, so there can be two parallel calls calls to ->uring_cmd (e.g. io-wq + cancel), which gives me shivers. Also, I'd rather no cancel in place requests of another task, io_submit_flush_completions() but it complicates things. Is there any argument against removing requests from the cancellation list in io_uring_try_cancel_uring_cmd() before calling ->uring_cmd? io_uring_try_cancel_uring_cmd() { lock(); for_each_req() { remove_req_from_cancel_list(req); req->file->uring_cmd(); } unlock(); } -- Pavel Begunkov