The current I/O dispatch mechanism - queueing I/O by adding it to the
io_cmds list (and poking task_work as needed), then dispatching it in
ublk server task context by reversing io_cmds and completing the
io_uring command associated to each one - was introduced by commit
7d4a93176e014 ("ublk_drv: don't forward io commands in reserve order")
to ensure that the ublk server received I/O in the same order that the
block layer submitted it to ublk_drv. This mechanism was only needed for
the "raw" task_work submission mechanism, since the io_uring task work
wrapper maintains FIFO ordering (using quite a similar mechanism in
fact). The "raw" task_work submission mechanism is no longer supported
in ublk_drv as of commit 29dc5d06613f2 ("ublk: kill queuing request by
task_work_add"), so the explicit llist/reversal is no longer needed - it
just duplicates logic already present in the underlying io_uring APIs.
Remove it.
Signed-off-by: Uday Shankar <ushankar@xxxxxxxxxxxxxxx>
---
drivers/block/ublk_drv.c | 46 +++++++++++-----------------------------------
1 file changed, 11 insertions(+), 35 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 2955900ee713c5d8f3cbc2a69f6f6058348e5253..82c9d3d22f0ea5a0fad3f33837fa16146b5af7a9 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -77,8 +77,6 @@
UBLK_PARAM_TYPE_DMA_ALIGN)
struct ublk_rq_data {
- struct llist_node node;
-
struct kref ref;
};
@@ -145,8 +143,6 @@ struct ublk_queue {
struct task_struct *ubq_daemon;
char *io_cmd_buf;
- struct llist_head io_cmds;
-
unsigned long io_addr; /* mapped vm address */
unsigned int max_io_sz;
bool force_abort;
@@ -1113,7 +1109,7 @@ static void ublk_complete_rq(struct kref *ref)
}
/*
- * Since __ublk_rq_task_work always fails requests immediately during
+ * Since ublk_rq_task_work_cb always fails requests immediately during
* exiting, __ublk_fail_req() is only called from abort context during
* exiting. So lock is unnecessary.
*
@@ -1159,11 +1155,14 @@ static inline void __ublk_abort_rq(struct ublk_queue *ubq,
blk_mq_end_request(rq, BLK_STS_IOERR);
}
-static inline void __ublk_rq_task_work(struct request *req,
- unsigned issue_flags)
+static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
{
- struct ublk_queue *ubq = req->mq_hctx->driver_data;
- int tag = req->tag;
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
+ struct ublk_queue *ubq = pdu->ubq;
+ int tag = pdu->tag;
+ struct request *req = blk_mq_tag_to_rq(
+ ubq->dev->tag_set.tags[ubq->q_id], tag);
struct ublk_io *io = &ubq->ios[tag];
unsigned int mapped_bytes;
@@ -1238,34 +1237,11 @@ static inline void __ublk_rq_task_work(struct request *req,
ubq_complete_io_cmd(io, UBLK_IO_RES_OK, issue_flags);
}
-static inline void ublk_forward_io_cmds(struct ublk_queue *ubq,
- unsigned issue_flags)
-{
- struct llist_node *io_cmds = llist_del_all(&ubq->io_cmds);
- struct ublk_rq_data *data, *tmp;
-
- io_cmds = llist_reverse_order(io_cmds);
- llist_for_each_entry_safe(data, tmp, io_cmds, node)
- __ublk_rq_task_work(blk_mq_rq_from_pdu(data), issue_flags);
-}
-
-static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd, unsigned issue_flags)
-{
- struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
- struct ublk_queue *ubq = pdu->ubq;
-
- ublk_forward_io_cmds(ubq, issue_flags);
-}
-
static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq)
{
- struct ublk_rq_data *data = blk_mq_rq_to_pdu(rq);
+ struct ublk_io *io = &ubq->ios[rq->tag];
- if (llist_add(&data->node, &ubq->io_cmds)) {
- struct ublk_io *io = &ubq->ios[rq->tag];
-
- io_uring_cmd_complete_in_task(io->cmd, ublk_rq_task_work_cb);
- }
+ io_uring_cmd_complete_in_task(io->cmd, ublk_rq_task_work_cb);
}
static enum blk_eh_timer_return ublk_timeout(struct request *rq)
@@ -1458,7 +1434,7 @@ static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq)
struct request *rq;
/*
- * Either we fail the request or ublk_rq_task_work_fn
+ * Either we fail the request or ublk_rq_task_work_cb
* will do it
*/
rq = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], i);
---
base-commit: 37f0c10318273bec83f373bbdad14fdc4e8ce79e
change-id: 20250318-ublk_io_cmds-a421653cefc2
Best regards,
--
Uday Shankar <ushankar@xxxxxxxxxxxxxxx>
