io_uring/kbuf.h

   1 // SPDX-License-Identifier: GPL-2.0
   2 #ifndef IOU_KBUF_H
   3 #define IOU_KBUF_H
   4
   5 #include <uapi/linux/io_uring.h>
   6
   7 struct io_buffer_list {
   8         /*
   9          * If ->buf_nr_pages is set, then buf_pages/buf_ring are used. If not,
  10          * then these are classic provided buffers and ->buf_list is used.
  11          */
  12         union {
  13                 struct list_head buf_list;
  14                 struct {
  15                         struct page **buf_pages;
  16                         struct io_uring_buf_ring *buf_ring;
  17                 };
  18         };
  19         __u16 bgid;
  20
  21         /* below is for ring provided buffers */
  22         __u16 buf_nr_pages;
  23         __u16 nr_entries;
  24         __u16 head;
  25         __u16 mask;
  26 };
  27
  28 struct io_buffer {
  29         struct list_head list;
  30         __u64 addr;
  31         __u32 len;
  32         __u16 bid;
  33         __u16 bgid;
  34 };
  35
  36 void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
  37                               unsigned int issue_flags);
  38 void io_destroy_buffers(struct io_ring_ctx *ctx);
  39
  40 int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
  41 int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags);
  42
  43 int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
  44 int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags);
  45
  46 int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg);
  47 int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg);
  48
  49 unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags);
  50
  51 void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags);
  52
  53 static inline void io_kbuf_recycle_ring(struct io_kiocb *req)
  54 {
  55         /*
  56          * We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
  57          * the flag and hence ensure that bl->head doesn't get incremented.
  58          * If the tail has already been incremented, hang on to it.
  59          * The exception is partial io, that case we should increment bl->head
  60          * to monopolize the buffer.
  61          */
  62         if (req->buf_list) {
  63                 if (req->flags & REQ_F_PARTIAL_IO) {
  64                         /*
  65                          * If we end up here, then the io_uring_lock has
  66                          * been kept held since we retrieved the buffer.
  67                          * For the io-wq case, we already cleared
  68                          * req->buf_list when the buffer was retrieved,
  69                          * hence it cannot be set here for that case.
  70                          */
  71                         req->buf_list->head++;
  72                         req->buf_list = NULL;
  73                 } else {
  74                         req->buf_index = req->buf_list->bgid;
  75                         req->flags &= ~REQ_F_BUFFER_RING;
  76                 }
  77         }
  78 }
  79
  80 static inline bool io_do_buffer_select(struct io_kiocb *req)
  81 {
  82         if (!(req->flags & REQ_F_BUFFER_SELECT))
  83                 return false;
  84         return !(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING));
  85 }
  86
  87 static inline void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
  88 {
  89         /*
  90          * READV uses fields in `struct io_rw` (len/addr) to stash the selected
  91          * buffer data. However if that buffer is recycled the original request
  92          * data stored in addr is lost. Therefore forbid recycling for now.
  93          */
  94         if (req->opcode == IORING_OP_READV)
  95                 return;
  96
  97         if (req->flags & REQ_F_BUFFER_SELECTED)
  98                 io_kbuf_recycle_legacy(req, issue_flags);
  99         if (req->flags & REQ_F_BUFFER_RING)
 100                 io_kbuf_recycle_ring(req);
 101 }
 102
 103 static inline unsigned int __io_put_kbuf_list(struct io_kiocb *req,
 104                                               struct list_head *list)
 105 {
 106         unsigned int ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
 107
 108         if (req->flags & REQ_F_BUFFER_RING) {
 109                 if (req->buf_list) {
 110                         req->buf_index = req->buf_list->bgid;
 111                         req->buf_list->head++;
 112                 }
 113                 req->flags &= ~REQ_F_BUFFER_RING;
 114         } else {
 115                 req->buf_index = req->kbuf->bgid;
 116                 list_add(&req->kbuf->list, list);
 117                 req->flags &= ~REQ_F_BUFFER_SELECTED;
 118         }
 119
 120         return ret;
 121 }
 122
 123 static inline unsigned int io_put_kbuf_comp(struct io_kiocb *req)
 124 {
 125         lockdep_assert_held(&req->ctx->completion_lock);
 126
 127         if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
 128                 return 0;
 129         return __io_put_kbuf_list(req, &req->ctx->io_buffers_comp);
 130 }
 131
 132 static inline unsigned int io_put_kbuf(struct io_kiocb *req,
 133                                        unsigned issue_flags)
 134 {
 135
 136         if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
 137                 return 0;
 138         return __io_put_kbuf(req, issue_flags);
 139 }
 140 #endif