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.
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| @@ -301,6 +301,16 @@ · 300 unmodified lines | ||
| 301 | 301 | */ |
| 302 | 302 | #define UBLK_F_PER_IO_DAEMON (1ULL << 13) |
| 303 | 303 | |
| 304 | +/* | |
| 305 | + * If this feature is set, UBLK_U_IO_REGISTER_IO_BUF/UBLK_U_IO_UNREGISTER_IO_BUF | |
| 306 | + * can be issued for an I/O on any task. q_id and tag are also ignored in | |
| 307 | + * UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd. | |
| 308 | + * If it is unset, zero-copy buffers can only be registered and unregistered by | |
| 309 | + * the I/O's daemon task. The q_id and tag of the registered buffer are required | |
| 310 | + * in UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd. | |
| 311 | + */ | |
| 312 | +#define UBLK_F_BUF_REG_OFF_DAEMON (1ULL << 14) | |
| 313 | + | |
| 304 | 314 | /* device state */ |
| 305 | 315 | #define UBLK_S_DEV_DEAD 0 |
| 306 | 316 | #define UBLK_S_DEV_LIVE 1 |