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ublk: store request pointer in ublk_io

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A ublk_io is converted to a request in several places in the I/O path by
using blk_mq_tag_to_rq() to look up the (qid, tag) on the ublk device's
tagset. This involves a bunch of dereferences and a tag bounds check.

To make this conversion cheaper, store the request pointer in ublk_io.
Overlap this storage with the io_uring_cmd pointer. This is safe because
the io_uring_cmd pointer is only valid if UBLK_IO_FLAG_ACTIVE is set on
the ublk_io, the request pointer is valid if UBLK_IO_FLAG_OWNED_BY_SRV,
and these flags are mutually exclusive.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250430225234.2676781-10-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Caleb Sander Mateos 2025-04-30 16:52:34 -06:00 committed by Jens Axboe
parent 8ed95b5470
commit 64d1dc522b
1 changed files with 24 additions and 19 deletions
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43
drivers/block/ublk_drv.c
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@ -142,7 +142,12 @@ struct ublk_io {
unsigned int flags;
int res;
struct io_uring_cmd *cmd;
union {
/* valid if UBLK_IO_FLAG_ACTIVE is set */
struct io_uring_cmd *cmd;
/* valid if UBLK_IO_FLAG_OWNED_BY_SRV is set */
struct request *req;
};
};
struct ublk_queue {
@ -1124,9 +1129,12 @@ static void ublk_complete_rq(struct kref *ref)
__ublk_complete_rq(req);
}
static void ublk_complete_io_cmd(struct ublk_io *io, int res,
unsigned issue_flags)
static void ublk_complete_io_cmd(struct ublk_io *io, struct request *req,
int res, unsigned issue_flags)
{
/* read cmd first because req will overwrite it */
struct io_uring_cmd *cmd = io->cmd;
/* mark this cmd owned by ublksrv */
io->flags |= UBLK_IO_FLAG_OWNED_BY_SRV;
@ -1136,8 +1144,10 @@ static void ublk_complete_io_cmd(struct ublk_io *io, int res,
*/
io->flags &= ~UBLK_IO_FLAG_ACTIVE;
io->req = req;
/* tell ublksrv one io request is coming */
io_uring_cmd_done(io->cmd, res, 0, issue_flags);
io_uring_cmd_done(cmd, res, 0, issue_flags);
}
#define UBLK_REQUEUE_DELAY_MS 3
@ -1215,7 +1225,7 @@ static void ublk_dispatch_req(struct ublk_queue *ubq,
io->flags |= UBLK_IO_FLAG_NEED_GET_DATA;
pr_devel("%s: need get data. qid %d tag %d io_flags %x\n",
__func__, ubq->q_id, req->tag, io->flags);
ublk_complete_io_cmd(io, UBLK_IO_RES_NEED_GET_DATA,
ublk_complete_io_cmd(io, req, UBLK_IO_RES_NEED_GET_DATA,
issue_flags);
return;
}
@ -1223,7 +1233,7 @@ static void ublk_dispatch_req(struct ublk_queue *ubq,
if (!ublk_start_io(ubq, req, io))
return;
ublk_complete_io_cmd(io, UBLK_IO_RES_OK, issue_flags);
ublk_complete_io_cmd(io, req, UBLK_IO_RES_OK, issue_flags);
}
static void ublk_cmd_tw_cb(struct io_uring_cmd *cmd,
@ -1611,12 +1621,8 @@ static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq)
for (i = 0; i < ubq->q_depth; i++) {
struct ublk_io *io = &ubq->ios[i];
if (io->flags & UBLK_IO_FLAG_OWNED_BY_SRV) {
struct request *rq;
rq = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], i);
__ublk_fail_req(ubq, io, rq);
}
if (io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)
__ublk_fail_req(ubq, io, io->req);
}
}
@ -1990,12 +1996,12 @@ 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 blk_mq_tags *tags = ubq->dev->tag_set.tags[ub_cmd->q_id];
struct request *req = blk_mq_tag_to_rq(tags, ub_cmd->tag);
struct request *req;
if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
return -EINVAL;
req = io->req;
if (ublk_need_map_io(ubq)) {
/*
* COMMIT_AND_FETCH_REQ has to provide IO buffer if
@ -2027,9 +2033,10 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
return 0;
}
static bool ublk_get_data(const struct ublk_queue *ubq, struct ublk_io *io,
struct request *req)
static bool ublk_get_data(const struct ublk_queue *ubq, struct ublk_io *io)
{
struct request *req = io->req;
/*
* We have handled UBLK_IO_NEED_GET_DATA command,
* so clear UBLK_IO_FLAG_NEED_GET_DATA now and just
@ -2055,7 +2062,6 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
u32 cmd_op = cmd->cmd_op;
unsigned tag = ub_cmd->tag;
int ret = -EINVAL;
struct request *req;
pr_devel("%s: received: cmd op %d queue %d tag %d result %d\n",
__func__, cmd->cmd_op, ub_cmd->q_id, tag,
@ -2111,8 +2117,7 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
goto out;
io->addr = ub_cmd->addr;
req = blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag);
if (!ublk_get_data(ubq, io, req))
if (!ublk_get_data(ubq, io))
return -EIOCBQUEUED;
return UBLK_IO_RES_OK;