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Mon, 18 Mar 2024 09:09:18 -0400 X-MC-Unique: 6Hpz_UPtNLuckTpbncqqJA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 417CE185A784; Mon, 18 Mar 2024 13:09:18 +0000 (UTC) Received: from fedora (unknown [10.72.116.15]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2722D2166B32; Mon, 18 Mar 2024 13:09:14 +0000 (UTC) Date: Mon, 18 Mar 2024 21:09:06 +0800 From: Ming Lei To: Pavel Begunkov Cc: io-uring@vger.kernel.org, linux-block@vger.kernel.org, Jens Axboe , Kanchan Joshi Subject: Re: [PATCH v2 03/14] io_uring/cmd: make io_uring_cmd_done irq safe Message-ID: References: <4c6a5b55-2833-4ef7-a514-577fe61160dd@gmail.com> <1f5c02ad-f25a-46ea-96e6-649997aea3c2@gmail.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1f5c02ad-f25a-46ea-96e6-649997aea3c2@gmail.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 On Mon, Mar 18, 2024 at 12:46:25PM +0000, Pavel Begunkov wrote: > On 3/18/24 11:59, Ming Lei wrote: > > On Mon, Mar 18, 2024 at 11:50:32AM +0000, Pavel Begunkov wrote: > > > On 3/18/24 08:10, Ming Lei wrote: > > > > On Mon, Mar 18, 2024 at 12:41:48AM +0000, Pavel Begunkov wrote: > > > > > io_uring_cmd_done() is called from the irq context and is considered to > > > > > be irq safe, however that's not the case if the driver requires > > > > > cancellations because io_uring_cmd_del_cancelable() could try to take > > > > > the uring_lock mutex. > > > > > > > > > > Clean up the confusion, by deferring cancellation handling to > > > > > locked task_work if we came into io_uring_cmd_done() from iowq > > > > > or other IO_URING_F_UNLOCKED path. > > > > > > > > > > Signed-off-by: Pavel Begunkov > > > > > --- > > > > > io_uring/uring_cmd.c | 24 +++++++++++++++++------- > > > > > 1 file changed, 17 insertions(+), 7 deletions(-) > > > > > > > > > > diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c > > > > > index ec38a8d4836d..9590081feb2d 100644 > > > > > --- a/io_uring/uring_cmd.c > > > > > +++ b/io_uring/uring_cmd.c > > > > > @@ -14,19 +14,18 @@ > > > > > #include "rsrc.h"on #include "uring_cmd.h" > > > > > -static void io_uring_cmd_del_cancelable(struct io_uring_cmd *cmd, > > > > > - unsigned int issue_flags) > > > > > +static void io_uring_cmd_del_cancelable(struct io_uring_cmd *cmd) > > > > > { > > > > > struct io_kiocb *req = cmd_to_io_kiocb(cmd); > > > > > struct io_ring_ctx *ctx = req->ctx; > > > > > + lockdep_assert_held(&ctx->uring_lock); > > > > > + > > > > > if (!(cmd->flags & IORING_URING_CMD_CANCELABLE)) > > > > > return; > > > > > cmd->flags &= ~IORING_URING_CMD_CANCELABLE; > > > > > - io_ring_submit_lock(ctx, issue_flags); > > > > > hlist_del(&req->hash_node); > > > > > - io_ring_submit_unlock(ctx, issue_flags); > > > > > } > > > > > /* > > > > > @@ -44,6 +43,9 @@ void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd, > > > > > struct io_kiocb *req = cmd_to_io_kiocb(cmd); > > > > > struct io_ring_ctx *ctx = req->ctx; > > > > > + if (WARN_ON_ONCE(ctx->flags & IORING_SETUP_IOPOLL)) > > > > > + return; > > > > > + > > > > > > > > This way limits cancelable command can't be used in iopoll context, and > > > > it isn't reasonable, and supporting iopoll has been in ublk todo list, > > > > especially single ring context is shared for both command and normal IO. > > > > > > That's something that can be solved when it's needed, and hence the > > > warning so it's not missed. That would need del_cancelable on the > > > ->iopoll side, but depends on the "leaving in cancel queue" > > > problem resolution. > > > > The current code is actually working with iopoll, so adding the warning > > can be one regression. Maybe someone has been using ublk with iopoll. > > Hmm, I don't see ->uring_cmd_iopoll implemented anywhere, and w/o > it io_uring should fail the request: > > int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags) > { > ... > if (ctx->flags & IORING_SETUP_IOPOLL) { > if (!file->f_op->uring_cmd_iopoll) > return -EOPNOTSUPP; > issue_flags |= IO_URING_F_IOPOLL; > } > } > > Did I miss it somewhere? Looks I missed the point, now the WARN() is fine. Thanks, Ming