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io_uring/kbuf: pass bgid to io_buffer_select()

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The current situation with buffer group id juggling is not ideal.
req->buf_index first stores the bgid, then it's overwritten by a buffer
id, and then it can get restored back no recycling / etc. It's not so
easy to control, and it's not handled consistently across request types
with receive requests saving and restoring the bgid it by hand.

It's a prep patch that adds a buffer group id argument to
io_buffer_select(). The caller will be responsible for stashing a copy
somewhere and passing it into the function.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a210d6427cc3f4f42271a6853274cd5a50e56820.1743437358.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2025-03-31 17:18:01 +01:00 • committed by Jens Axboe
parent e6f74fd67d
commit c0e9650521
5 changed files with 13 additions and 9 deletions
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4
io_uring/kbuf.c
View file

@ -193,7 +193,7 @@ static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
}
void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
unsigned int issue_flags)
unsigned buf_group, unsigned int issue_flags)
{
struct io_ring_ctx *ctx = req->ctx;
struct io_buffer_list *bl;
@ -201,7 +201,7 @@ void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
io_ring_submit_lock(req->ctx, issue_flags);
bl = io_buffer_get_list(ctx, req->buf_index);
bl = io_buffer_get_list(ctx, buf_group);
if (likely(bl)) {
if (bl->flags & IOBL_BUF_RING)
ret = io_ring_buffer_select(req, len, bl, issue_flags);

2
io_uring/kbuf.h
View file

@ -58,7 +58,7 @@ struct buf_sel_arg {
};
void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
unsigned int issue_flags);
unsigned buf_group, unsigned int issue_flags);
int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
unsigned int issue_flags);
int io_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg);

9
io_uring/net.c
View file

@ -407,13 +407,12 @@ int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
if (sr->msg_flags & MSG_DONTWAIT)
req->flags |= REQ_F_NOWAIT;
if (req->flags & REQ_F_BUFFER_SELECT)
sr->buf_group = req->buf_index;
if (sr->flags & IORING_RECVSEND_BUNDLE) {
if (req->opcode == IORING_OP_SENDMSG)
return -EINVAL;
if (!(req->flags & REQ_F_BUFFER_SELECT))
return -EINVAL;
sr->msg_flags |= MSG_WAITALL;
sr->buf_group = req->buf_index;
req->buf_list = NULL;
req->flags |= REQ_F_MULTISHOT;
}
@ -979,7 +978,7 @@ retry_multishot:
void __user *buf;
size_t len = sr->len;
buf = io_buffer_select(req, &len, issue_flags);
buf = io_buffer_select(req, &len, sr->buf_group, issue_flags);
if (!buf)
return -ENOBUFS;
@ -1089,7 +1088,7 @@ static int io_recv_buf_select(struct io_kiocb *req, struct io_async_msghdr *kmsg
void __user *buf;
*len = sr->len;
buf = io_buffer_select(req, len, issue_flags);
buf = io_buffer_select(req, len, sr->buf_group, issue_flags);
if (!buf)
return -ENOBUFS;
sr->buf = buf;

5
io_uring/rw.c
View file

@ -119,7 +119,7 @@ static int __io_import_rw_buffer(int ddir, struct io_kiocb *req,
return io_import_vec(ddir, req, io, buf, sqe_len);
if (io_do_buffer_select(req)) {
buf = io_buffer_select(req, &sqe_len, issue_flags);
buf = io_buffer_select(req, &sqe_len, io->buf_group, issue_flags);
if (!buf)
return -ENOBUFS;
rw->addr = (unsigned long) buf;
@ -253,16 +253,19 @@ static int __io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
int ddir)
{
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
struct io_async_rw *io;
unsigned ioprio;
u64 attr_type_mask;
int ret;
if (io_rw_alloc_async(req))
return -ENOMEM;
io = req->async_data;
rw->kiocb.ki_pos = READ_ONCE(sqe->off);
/* used for fixed read/write too - just read unconditionally */
req->buf_index = READ_ONCE(sqe->buf_index);
io->buf_group = req->buf_index;
ioprio = READ_ONCE(sqe->ioprio);
if (ioprio) {

2
io_uring/rw.h
View file

@ -16,6 +16,8 @@ struct io_async_rw {
struct iov_iter iter;
struct iov_iter_state iter_state;
struct iovec fast_iov;
unsigned buf_group;
/*
* wpq is for buffered io, while meta fields are used with
* direct io