linux-stable/io_uring/kbuf.h
Jens Axboe c56e022c0a io_uring: add support for user mapped provided buffer ring
The ring mapped provided buffer rings rely on the application allocating
the memory for the ring, and then the kernel will map it. This generally
works fine, but runs into issues on some architectures where we need
to be able to ensure that the kernel and application virtual address for
the ring play nicely together. This at least impacts architectures that
set SHM_COLOUR, but potentially also anyone setting SHMLBA.

To use this variant of ring provided buffers, the application need not
allocate any memory for the ring. Instead the kernel will do so, and
the allocation must subsequently call mmap(2) on the ring with the
offset set to:

	IORING_OFF_PBUF_RING | (bgid << IORING_OFF_PBUF_SHIFT)

to get a virtual address for the buffer ring. Normally the application
would allocate a suitable piece of memory (and correctly aligned) and
simply pass that in via io_uring_buf_reg.ring_addr and the kernel would
map it.

Outside of the setup differences, the kernel allocate + user mapped
provided buffer ring works exactly the same.

Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-04-03 07:14:21 -06:00

139 lines
3.8 KiB
C

// SPDX-License-Identifier: GPL-2.0
#ifndef IOU_KBUF_H
#define IOU_KBUF_H
#include <uapi/linux/io_uring.h>
struct io_buffer_list {
/*
* If ->buf_nr_pages is set, then buf_pages/buf_ring are used. If not,
* then these are classic provided buffers and ->buf_list is used.
*/
union {
struct list_head buf_list;
struct {
struct page **buf_pages;
struct io_uring_buf_ring *buf_ring;
};
};
__u16 bgid;
/* below is for ring provided buffers */
__u16 buf_nr_pages;
__u16 nr_entries;
__u16 head;
__u16 mask;
/* ring mapped provided buffers */
__u8 is_mapped;
/* ring mapped provided buffers, but mmap'ed by application */
__u8 is_mmap;
};
struct io_buffer {
struct list_head list;
__u64 addr;
__u32 len;
__u16 bid;
__u16 bgid;
};
void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
unsigned int issue_flags);
void io_destroy_buffers(struct io_ring_ctx *ctx);
int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags);
int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags);
int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg);
int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg);
unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags);
void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags);
void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid);
static inline void io_kbuf_recycle_ring(struct io_kiocb *req)
{
/*
* We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
* the flag and hence ensure that bl->head doesn't get incremented.
* If the tail has already been incremented, hang on to it.
* The exception is partial io, that case we should increment bl->head
* to monopolize the buffer.
*/
if (req->buf_list) {
if (req->flags & REQ_F_PARTIAL_IO) {
/*
* If we end up here, then the io_uring_lock has
* been kept held since we retrieved the buffer.
* For the io-wq case, we already cleared
* req->buf_list when the buffer was retrieved,
* hence it cannot be set here for that case.
*/
req->buf_list->head++;
req->buf_list = NULL;
} else {
req->buf_index = req->buf_list->bgid;
req->flags &= ~REQ_F_BUFFER_RING;
}
}
}
static inline bool io_do_buffer_select(struct io_kiocb *req)
{
if (!(req->flags & REQ_F_BUFFER_SELECT))
return false;
return !(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING));
}
static inline void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
{
if (req->flags & REQ_F_BUFFER_SELECTED)
io_kbuf_recycle_legacy(req, issue_flags);
if (req->flags & REQ_F_BUFFER_RING)
io_kbuf_recycle_ring(req);
}
static inline unsigned int __io_put_kbuf_list(struct io_kiocb *req,
struct list_head *list)
{
unsigned int ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
if (req->flags & REQ_F_BUFFER_RING) {
if (req->buf_list) {
req->buf_index = req->buf_list->bgid;
req->buf_list->head++;
}
req->flags &= ~REQ_F_BUFFER_RING;
} else {
req->buf_index = req->kbuf->bgid;
list_add(&req->kbuf->list, list);
req->flags &= ~REQ_F_BUFFER_SELECTED;
}
return ret;
}
static inline unsigned int io_put_kbuf_comp(struct io_kiocb *req)
{
lockdep_assert_held(&req->ctx->completion_lock);
if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
return 0;
return __io_put_kbuf_list(req, &req->ctx->io_buffers_comp);
}
static inline unsigned int io_put_kbuf(struct io_kiocb *req,
unsigned issue_flags)
{
if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
return 0;
return __io_put_kbuf(req, issue_flags);
}
#endif