Currently, UBLK_IO_REGISTER_IO_BUF and UBLK_IO_UNREGISTER_IO_BUF are
only permitted on the ublk_io's daemon task. But this restriction is
unnecessary. ublk_register_io_buf() calls __ublk_check_and_get_req() to
look up the request from the tagset and atomically take a reference on
the request without accessing the ublk_io. ublk_unregister_io_buf()
doesn't use the q_id or tag at all.
So allow these opcodes even on tasks other than io->task.
Handle UBLK_IO_UNREGISTER_IO_BUF before obtaining the ubq and io since
the buffer index being unregistered is not necessarily related to the
specified q_id and tag.
Add a feature flag UBLK_F_BUF_REG_OFF_DAEMON that userspace can use to
determine whether the kernel supports off-daemon buffer registration.
Suggested-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
---
drivers/block/ublk_drv.c | 27 ++++++++++++++++++++++-----
include/uapi/linux/ublk_cmd.h | 10 ++++++++++
2 files changed, 32 insertions(+), 5 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 237d50490923..11aa65f36ec9 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -68,11 +68,12 @@
| UBLK_F_ZONED \
| UBLK_F_USER_RECOVERY_FAIL_IO \
| UBLK_F_UPDATE_SIZE \
| UBLK_F_AUTO_BUF_REG \
| UBLK_F_QUIESCE \
- | UBLK_F_PER_IO_DAEMON)
+ | UBLK_F_PER_IO_DAEMON \
+ | UBLK_F_BUF_REG_OFF_DAEMON)
#define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
| UBLK_F_USER_RECOVERY_REISSUE \
| UBLK_F_USER_RECOVERY_FAIL_IO)
@@ -2186,10 +2187,18 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
ret = ublk_check_cmd_op(cmd_op);
if (ret)
goto out;
+ /*
+ * io_buffer_unregister_bvec() doesn't access the ubq or io,
+ * so no need to validate the q_id, tag, or task
+ */
+ if (_IOC_NR(cmd_op) == UBLK_IO_UNREGISTER_IO_BUF)
+ return ublk_unregister_io_buf(cmd, ub, ub_cmd->addr,
+ issue_flags);
+
ret = -EINVAL;
if (ub_cmd->q_id >= ub->dev_info.nr_hw_queues)
goto out;
ubq = ublk_get_queue(ub, ub_cmd->q_id);
@@ -2206,12 +2215,21 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
ublk_prep_cancel(cmd, issue_flags, ubq, tag);
return -EIOCBQUEUED;
}
- if (READ_ONCE(io->task) != current)
+ if (READ_ONCE(io->task) != current) {
+ /*
+ * ublk_register_io_buf() accesses only the io's refcount,
+ * so can be handled on any task
+ */
+ if (_IOC_NR(cmd_op) == UBLK_IO_REGISTER_IO_BUF)
+ return ublk_register_io_buf(cmd, ubq, io, ub_cmd->addr,
+ issue_flags);
+
goto out;
+ }
/* there is pending io cmd, something must be wrong */
if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)) {
ret = -EBUSY;
goto out;
@@ -2226,12 +2244,10 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
goto out;
switch (_IOC_NR(cmd_op)) {
case UBLK_IO_REGISTER_IO_BUF:
return ublk_register_io_buf(cmd, ubq, io, ub_cmd->addr, issue_flags);
- case UBLK_IO_UNREGISTER_IO_BUF:
- return ublk_unregister_io_buf(cmd, ub, ub_cmd->addr, issue_flags);
case UBLK_IO_COMMIT_AND_FETCH_REQ:
ret = ublk_commit_and_fetch(ubq, io, cmd, ub_cmd, issue_flags);
if (ret)
goto out;
@@ -2932,11 +2948,12 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
*/
ub->dev_info.flags &= UBLK_F_ALL;
ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE |
UBLK_F_URING_CMD_COMP_IN_TASK |
- UBLK_F_PER_IO_DAEMON;
+ UBLK_F_PER_IO_DAEMON |
+ UBLK_F_BUF_REG_OFF_DAEMON;
/* GET_DATA isn't needed any more with USER_COPY or ZERO COPY */
if (ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY |
UBLK_F_AUTO_BUF_REG))
ub->dev_info.flags &= ~UBLK_F_NEED_GET_DATA;
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 77d9d6af46da..a7b52f6c1ba4 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -279,10 +279,20 @@
* (qid1,tag1) and (qid2,tag2), if qid1 == qid2, then the same task must
* be responsible for handling (qid1,tag1) and (qid2,tag2).
*/
#define UBLK_F_PER_IO_DAEMON (1ULL << 13)
+/*
+ * If this feature is set, UBLK_U_IO_REGISTER_IO_BUF/UBLK_U_IO_UNREGISTER_IO_BUF
+ * can be issued for an I/O on any task. q_id and tag are also ignored in
+ * UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd.
+ * If it is unset, zero-copy buffers can only be registered and unregistered by
+ * the I/O's daemon task. The q_id and tag of the registered buffer are required
+ * in UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd.
+ */
+#define UBLK_F_BUF_REG_OFF_DAEMON (1ULL << 14)
+
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
#define UBLK_S_DEV_QUIESCED 2
#define UBLK_S_DEV_FAIL_IO 3
--
2.45.2
