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man/io_uring_register.2: add newer registration opcodes

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This adds a description of IORING_REGISTER_PBUF_RING,
IORING_UNREGISTER_PBUF_RING, and IORING_REGISTER_SYNC_CANCEL. Still
missing at this point in time is IORING_REGISTER_FILE_ALLOC_RANGE.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2022-10-20 07:46:47 -07:00
parent 2f83d15a2e
commit 8e29ba8d93
1 changed files with 96 additions and 0 deletions
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man/io_uring_register.2
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@@ -579,6 +579,102 @@ slot, making it available for future use.
Available since 5.18.
.TP
.B IORING_REGISTER_PBUF_RING
Registers a shared buffer ring to be used with provided buffers. This is a
newer alternative to using
.B IORING_OP_PROVIDE_BUFFERS
which is more efficient, to be used with request types that support the
.B IOSQE_BUFFER_SELECT
flag.
The
.I arg
argument must be filled in with the appropriate information. It looks as
follows:
.PP
.in +12n
.EX
struct io_uring_buf_reg {
__u64 ring_addr;
__u32 ring_entries;
__u16 bgid;
__u16 pad;
__u64 resv[3];
};
.EE
.in
.PP
.in +8n
The
.I ring_addr
field must contain the address to the memory allocated to fit this ring.
The memory must be page aligned and hence allocated appropriately using eg
.BR posix_memalign (3)
or similar. The size of the ring is the product of
.I ring_entries
and the size of
.IR "struct io_uring_buf" .
.I ring_entries
is the desired size of the ring, and must be a power-of-2 in size. The maximum
size allowed is 2^15 (32768).
.I bgid
is the buffer group ID associated with this ring. SQEs that select a buffer
has a buffer group associated with them in their
.I buf_group
field, and the associated CQE will have
.B IORING_CQE_F_BUFFER
set in their
.I flags
member, which will also contain the specific ID of the buffer selected. The rest
of the fields are reserved and must be cleared to zero.
The
.I flags
argument is currently unused and must be set to zero.
.i nr_args
must be set to 1.
Also see
.BR io_uring_register_buf_ring (3)
for more details. Available since 5.19.
.TP
.B IORING_UNREGISTER_PBUF_RING
Unregister a previously registered provided buffer ring.
.I arg
must be set to the address of a struct io_uring_buf_reg, with just the
.I bgid
field set to the buffer group ID of the previously registered provided buffer
group.
.I nr_args
must be set to 1. Also see
.B IORING_REGISTER_PBUF_RING .
Available since 5.19.
.TP
.B IORING_REGISTER_SYNC_CANCEL
Performs a synchronous cancelation request, which works in a similar fashion to
.B IORING_OP_ASYNC_CANCEL
except it completes inline. This can be useful for scenarios where cancelations
should happen synchronously, rather than needing to issue an SQE and wait for
completion of that specific CQE.
.I arg
must be set to a pointer to a struct io_uring_sync_cancel_reg structure, with
the details filled in for what request(s) to target for cancelation. See
.BR io_uring_register_sync_cancel (3)
for details on that. The return values are the same, except they are passed
back synchronously rather than through the CQE
.I res
field.
.I nr_args
must be set to 1.
Available since 6.0.
.SH RETURN VALUE
On success,