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([2620:10d:c092:600::1:429a]) by smtp.gmail.com with ESMTPSA id bw9-20020a170906c1c900b00a45ff821e09sm4892778ejb.150.2024.03.18.07.33.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Mar 2024 07:33:58 -0700 (PDT) Message-ID: <8bf6d549-cf66-4412-bebd-fd6e98166552@gmail.com> Date: Mon, 18 Mar 2024 14:32:16 +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> <2095ac3e-5e5f-4ea2-a906-a924a25c121a@gmail.com> In-Reply-To: <2095ac3e-5e5f-4ea2-a906-a924a25c121a@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 3/18/24 13:37, Pavel Begunkov wrote: > 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. I'm wrong though on flush_completions, the task there cancels only its own requests io_uring_try_cancel_uring_cmd() { ... if (!cancel_all && req->task != task) continue; } > 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