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Wed, 16 Apr 2025 12:46:17 -0700 (PDT) X-Relaying-Domain: purestorage.com Received: from dev-ushankar.dev.purestorage.com (dev-ushankar.dev.purestorage.com [IPv6:2620:125:9007:640:7:70:36:0]) by c7-smtp-2023.dev.purestorage.com (Postfix) with ESMTP id 9097934058D; Wed, 16 Apr 2025 13:46:16 -0600 (MDT) Received: by dev-ushankar.dev.purestorage.com (Postfix, from userid 1557716368) id 87502E417E1; Wed, 16 Apr 2025 13:46:16 -0600 (MDT) From: Uday Shankar Date: Wed, 16 Apr 2025 13:46:06 -0600 Subject: [PATCH v5 2/4] ublk: mark ublk_queue as const for ublk_commit_and_fetch Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250416-ublk_task_per_io-v5-2-9261ad7bff20@purestorage.com> References: <20250416-ublk_task_per_io-v5-0-9261ad7bff20@purestorage.com> In-Reply-To: <20250416-ublk_task_per_io-v5-0-9261ad7bff20@purestorage.com> To: Ming Lei , Jens Axboe , Caleb Sander Mateos Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Uday Shankar X-Mailer: b4 0.14.2 We now allow multiple tasks to operate on I/Os belonging to the same queue concurrently. This means that any writes to ublk_queue in the I/O path are potential sources of data races. Try to prevent these by marking ublk_queue pointers as const when handling COMMIT_AND_FETCH. Move the logic for this command into its own function ublk_commit_and_fetch. Also open code ublk_commit_completion in ublk_commit_and_fetch to reduce the number of parameters/avoid a redundant lookup. Suggested-by: Ming Lei Signed-off-by: Uday Shankar Reviewed-by: Caleb Sander Mateos --- drivers/block/ublk_drv.c | 91 +++++++++++++++++++++++---------------------= ---- 1 file changed, 43 insertions(+), 48 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 4e4863d873e6593ad94c72cbf971f792df5795ae..b44cbcbcc9d1735c398dc9ac7e9= 3f4c8736b9201 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -1518,30 +1518,6 @@ static int ublk_ch_mmap(struct file *filp, struct vm= _area_struct *vma) return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot); } =20 -static void ublk_commit_completion(struct ublk_device *ub, - const struct ublksrv_io_cmd *ub_cmd) -{ - u32 qid =3D ub_cmd->q_id, tag =3D ub_cmd->tag; - struct ublk_queue *ubq =3D ublk_get_queue(ub, qid); - struct ublk_io *io =3D &ubq->ios[tag]; - struct request *req; - - /* now this cmd slot is owned by nbd driver */ - io->flags &=3D ~UBLK_IO_FLAG_OWNED_BY_SRV; - io->res =3D ub_cmd->result; - - /* find the io request and complete */ - req =3D blk_mq_tag_to_rq(ub->tag_set.tags[qid], tag); - if (WARN_ON_ONCE(unlikely(!req))) - return; - - if (req_op(req) =3D=3D REQ_OP_ZONE_APPEND) - req->__sector =3D ub_cmd->zone_append_lba; - - if (likely(!blk_should_fake_timeout(req->q))) - ublk_put_req_ref(ubq, req); -} - /* * Called from io task context via cancel fn, meantime quiesce ublk * blk-mq queue, so we are called exclusively with blk-mq and io task @@ -1918,6 +1894,45 @@ static int ublk_unregister_io_buf(struct io_uring_cm= d *cmd, return io_buffer_unregister_bvec(cmd, index, issue_flags); } =20 +static int ublk_commit_and_fetch(const struct ublk_queue *ubq, + struct ublk_io *io, struct io_uring_cmd *cmd, + const struct ublksrv_io_cmd *ub_cmd, + struct request *req) +{ + if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)) + return -EINVAL; + + if (ublk_need_map_io(ubq)) { + /* + * COMMIT_AND_FETCH_REQ has to provide IO buffer if + * NEED GET DATA is not enabled or it is Read IO. + */ + if (!ub_cmd->addr && (!ublk_need_get_data(ubq) || + req_op(req) =3D=3D REQ_OP_READ)) + return -EINVAL; + } else if (req_op(req) !=3D REQ_OP_ZONE_APPEND && ub_cmd->addr) { + /* + * User copy requires addr to be unset when command is + * not zone append + */ + return -EINVAL; + } + + ublk_fill_io_cmd(io, cmd, ub_cmd->addr); + + /* now this cmd slot is owned by ublk driver */ + io->flags &=3D ~UBLK_IO_FLAG_OWNED_BY_SRV; + io->res =3D ub_cmd->result; + + if (req_op(req) =3D=3D REQ_OP_ZONE_APPEND) + req->__sector =3D ub_cmd->zone_append_lba; + + if (likely(!blk_should_fake_timeout(req->q))) + ublk_put_req_ref(ubq, req); + + return 0; +} + static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags, const struct ublksrv_io_cmd *ub_cmd) @@ -1929,7 +1944,6 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *c= md, u32 cmd_op =3D cmd->cmd_op; unsigned tag =3D ub_cmd->tag; int ret =3D -EINVAL; - struct request *req; =20 pr_devel("%s: received: cmd op %d queue %d tag %d result %d\n", __func__, cmd->cmd_op, ub_cmd->q_id, tag, @@ -2005,30 +2019,11 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd = *cmd, ublk_mark_io_ready(ub, ubq); break; case UBLK_IO_COMMIT_AND_FETCH_REQ: - req =3D blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag); - - if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)) - goto out; - - if (ublk_need_map_io(ubq)) { - /* - * COMMIT_AND_FETCH_REQ has to provide IO buffer if - * NEED GET DATA is not enabled or it is Read IO. - */ - if (!ub_cmd->addr && (!ublk_need_get_data(ubq) || - req_op(req) =3D=3D REQ_OP_READ)) - goto out; - } else if (req_op(req) !=3D REQ_OP_ZONE_APPEND && ub_cmd->addr) { - /* - * User copy requires addr to be unset when command is - * not zone append - */ - ret =3D -EINVAL; + ret =3D ublk_commit_and_fetch( + ubq, io, cmd, ub_cmd, + blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag)); + if (ret) goto out; - } - - ublk_fill_io_cmd(io, cmd, ub_cmd->addr); - ublk_commit_completion(ub, ub_cmd); break; case UBLK_IO_NEED_GET_DATA: if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)) --=20 2.34.1