From 763ff02ce287c2e5c8a012d40bd2f3dab99ae5d5 Mon Sep 17 00:00:00 2001 From: Caleb Sander Mateos Date: Fri, 20 Jun 2025 09:10:03 -0600 Subject: ublk: allow UBLK_IO_(UN)REGISTER_IO_BUF on any task 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 Signed-off-by: Caleb Sander Mateos Reviewed-by: Ming Lei Link: https://lore.kernel.org/r/20250620151008.3976463-10-csander@purestorage.com Signed-off-by: Jens Axboe --- include/uapi/linux/ublk_cmd.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/uapi') diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index c9751bdfd937..ec77dabba45b 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -301,6 +301,16 @@ */ #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 -- cgit v1.2.3