* [PATCH V2 1/2] io_uring: add helper io_uring_cmd_ctx_handle()
2025-05-22 15:20 [PATCH V2 0/2] ublk: run auto buf unregister on same io_ring_ctx with register Ming Lei
@ 2025-05-22 15:20 ` Ming Lei
2025-05-22 15:23 ` Caleb Sander Mateos
2025-05-22 15:20 ` [PATCH V2 2/2] ublk: run auto buf unregisgering in same io_ring_ctx with registering Ming Lei
2025-05-22 16:06 ` [PATCH V2 0/2] ublk: run auto buf unregister on same io_ring_ctx with register Jens Axboe
2 siblings, 1 reply; 5+ messages in thread
From: Ming Lei @ 2025-05-22 15:20 UTC (permalink / raw)
To: Jens Axboe, linux-block, io-uring
Cc: Uday Shankar, Caleb Sander Mateos, Ming Lei
Add helper io_uring_cmd_ctx_handle() for driver to track per-context
resource, such as registered kernel io buffer.
Suggested-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/io_uring/cmd.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 0634a3de1782..53408124c1e5 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -140,6 +140,15 @@ static inline struct io_uring_cmd_data *io_uring_cmd_get_async_data(struct io_ur
return cmd_to_io_kiocb(cmd)->async_data;
}
+/*
+ * Return uring_cmd's context reference as its context handle for driver to
+ * track per-context resource, such as registered kernel IO buffer
+ */
+static inline void *io_uring_cmd_ctx_handle(struct io_uring_cmd *cmd)
+{
+ return cmd_to_io_kiocb(cmd)->ctx;
+}
+
int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
void (*release)(void *), unsigned int index,
unsigned int issue_flags);
--
2.47.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH V2 2/2] ublk: run auto buf unregisgering in same io_ring_ctx with registering
2025-05-22 15:20 [PATCH V2 0/2] ublk: run auto buf unregister on same io_ring_ctx with register Ming Lei
2025-05-22 15:20 ` [PATCH V2 1/2] io_uring: add helper io_uring_cmd_ctx_handle() Ming Lei
@ 2025-05-22 15:20 ` Ming Lei
2025-05-22 16:06 ` [PATCH V2 0/2] ublk: run auto buf unregister on same io_ring_ctx with register Jens Axboe
2 siblings, 0 replies; 5+ messages in thread
From: Ming Lei @ 2025-05-22 15:20 UTC (permalink / raw)
To: Jens Axboe, linux-block, io-uring
Cc: Uday Shankar, Caleb Sander Mateos, Ming Lei
UBLK_F_AUTO_BUF_REG requires that the buffer registered automatically
is unregistered in same `io_ring_ctx`, so check it explicitly.
Document this requirement for UBLK_F_AUTO_BUF_REG.
Drop WARN_ON_ONCE() which is triggered from userspace code path.
Fixes: 99c1e4eb6a3f ("ublk: register buffer to local io_uring with provided buf index via UBLK_F_AUTO_BUF_REG")
Reported-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/block/ublk_drv.c | 19 ++++++++++++++++---
include/uapi/linux/ublk_cmd.h | 6 +++++-
2 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index fcf568b89370..f44ac5526edd 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -84,6 +84,7 @@ struct ublk_rq_data {
/* for auto-unregister buffer in case of UBLK_F_AUTO_BUF_REG */
u16 buf_index;
+ void *buf_ctx_handle;
};
struct ublk_uring_cmd_pdu {
@@ -1211,6 +1212,8 @@ static bool ublk_auto_buf_reg(struct request *req, struct ublk_io *io,
}
/* one extra reference is dropped by ublk_io_release */
refcount_set(&data->ref, 2);
+
+ data->buf_ctx_handle = io_uring_cmd_ctx_handle(io->cmd);
/* store buffer index in request payload */
data->buf_index = pdu->buf.index;
io->flags |= UBLK_IO_FLAG_AUTO_BUF_REG;
@@ -2111,12 +2114,22 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
if (ublk_support_auto_buf_reg(ubq)) {
int ret;
+ /*
+ * `UBLK_F_AUTO_BUF_REG` only works iff `UBLK_IO_FETCH_REQ`
+ * and `UBLK_IO_COMMIT_AND_FETCH_REQ` are issued from same
+ * `io_ring_ctx`.
+ *
+ * If this uring_cmd's io_ring_ctx isn't same with the
+ * one for registering the buffer, it is ublk server's
+ * responsibility for unregistering the buffer, otherwise
+ * this ublk request gets stuck.
+ */
if (io->flags & UBLK_IO_FLAG_AUTO_BUF_REG) {
struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
- WARN_ON_ONCE(io_buffer_unregister_bvec(cmd,
- data->buf_index,
- issue_flags));
+ if (data->buf_ctx_handle == io_uring_cmd_ctx_handle(cmd))
+ io_buffer_unregister_bvec(cmd, data->buf_index,
+ issue_flags);
io->flags &= ~UBLK_IO_FLAG_AUTO_BUF_REG;
}
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index c4b9942697fc..1c40632cb164 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -226,7 +226,11 @@
*
* For using this feature:
*
- * - ublk server has to create sparse buffer table
+ * - ublk server has to create sparse buffer table on the same `io_ring_ctx`
+ * for issuing `UBLK_IO_FETCH_REQ` and `UBLK_IO_COMMIT_AND_FETCH_REQ`.
+ * If uring_cmd isn't issued on same `io_ring_ctx`, it is ublk server's
+ * responsibility to unregister the buffer by issuing `IO_UNREGISTER_IO_BUF`
+ * manually, otherwise this ublk request won't complete.
*
* - ublk server passes auto buf register data via uring_cmd's sqe->addr,
* `struct ublk_auto_buf_reg` is populated from sqe->addr, please see
--
2.47.0
^ permalink raw reply related [flat|nested] 5+ messages in thread