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io_uring: allow buffer recycling in READV 

In commit 934447a603 ("io_uring: do not recycle buffer in READV") a
temporary fix was put in io_kbuf_recycle to simply never recycle READV
buffers.

Instead of that, rather treat READV with REQ_F_BUFFER_SELECTED the same as
a READ with REQ_F_BUFFER_SELECTED. Since READV requires iov_len of 1 they
are essentially the same.
In order to do this inside io_prep_rw() add some validation to check that
it is in fact only length 1, and also extract the length of the buffer at
prep time.

This allows removal of the io_iov_buffer_select codepaths as they are only
used from the READV op.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220907165152.994979-1-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dylan Yudaken 2022-09-07 09:51:52 -07:00 committed by Jens Axboe
parent de97fcb303
commit 4ab9d46507
2 changed files with 52 additions and 94 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
io_uring/kbuf.h
View File

@ -86,18 +86,6 @@ static inline bool io_do_buffer_select(struct io_kiocb *req)
static inline void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
{
/*
* READV uses fields in `struct io_rw` (len/addr) to stash the selected
* buffer data. However if that buffer is recycled the original request
* data stored in addr is lost. Therefore forbid recycling for now.
*/
if (req->opcode == IORING_OP_READV) {
if ((req->flags & REQ_F_BUFFER_RING) && req->buf_list) {
req->buf_list->head++;
req->buf_list = NULL;
}
return;
}
if (req->flags & REQ_F_BUFFER_SELECTED)
io_kbuf_recycle_legacy(req, issue_flags);
if (req->flags & REQ_F_BUFFER_RING)

134
io_uring/rw.c
View File

@ -33,6 +33,46 @@ static inline bool io_file_supports_nowait(struct io_kiocb *req)
return req->flags & REQ_F_SUPPORT_NOWAIT;
}
#ifdef CONFIG_COMPAT
static int io_iov_compat_buffer_select_prep(struct io_rw *rw)
{
struct compat_iovec __user *uiov;
compat_ssize_t clen;
uiov = u64_to_user_ptr(rw->addr);
if (!access_ok(uiov, sizeof(*uiov)))
return -EFAULT;
if (__get_user(clen, &uiov->iov_len))
return -EFAULT;
if (clen < 0)
return -EINVAL;
rw->len = clen;
return 0;
}
#endif
static int io_iov_buffer_select_prep(struct io_kiocb *req)
{
struct iovec __user *uiov;
struct iovec iov;
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
if (rw->len != 1)
return -EINVAL;
#ifdef CONFIG_COMPAT
if (req->ctx->compat)
return io_iov_compat_buffer_select_prep(rw);
#endif
uiov = u64_to_user_ptr(rw->addr);
if (copy_from_user(&iov, uiov, sizeof(*uiov)))
return -EFAULT;
rw->len = iov.iov_len;
return 0;
}
int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
@ -69,6 +109,16 @@ int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
rw->addr = READ_ONCE(sqe->addr);
rw->len = READ_ONCE(sqe->len);
rw->flags = READ_ONCE(sqe->rw_flags);
/* Have to do this validation here, as this is in io_read() rw->len might
* have chanaged due to buffer selection
*/
if (req->opcode == IORING_OP_READV && req->flags & REQ_F_BUFFER_SELECT) {
ret = io_iov_buffer_select_prep(req);
if (ret)
return ret;
}
return 0;
}
@ -279,79 +329,6 @@ static int kiocb_done(struct io_kiocb *req, ssize_t ret,
return IOU_ISSUE_SKIP_COMPLETE;
}
#ifdef CONFIG_COMPAT
static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
unsigned int issue_flags)
{
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
struct compat_iovec __user *uiov;
compat_ssize_t clen;
void __user *buf;
size_t len;
uiov = u64_to_user_ptr(rw->addr);
if (!access_ok(uiov, sizeof(*uiov)))
return -EFAULT;
if (__get_user(clen, &uiov->iov_len))
return -EFAULT;
if (clen < 0)
return -EINVAL;
len = clen;
buf = io_buffer_select(req, &len, issue_flags);
if (!buf)
return -ENOBUFS;
rw->addr = (unsigned long) buf;
iov[0].iov_base = buf;
rw->len = iov[0].iov_len = (compat_size_t) len;
return 0;
}
#endif
static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
unsigned int issue_flags)
{
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
struct iovec __user *uiov = u64_to_user_ptr(rw->addr);
void __user *buf;
ssize_t len;
if (copy_from_user(iov, uiov, sizeof(*uiov)))
return -EFAULT;
len = iov[0].iov_len;
if (len < 0)
return -EINVAL;
buf = io_buffer_select(req, &len, issue_flags);
if (!buf)
return -ENOBUFS;
rw->addr = (unsigned long) buf;
iov[0].iov_base = buf;
rw->len = iov[0].iov_len = len;
return 0;
}
static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
unsigned int issue_flags)
{
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) {
iov[0].iov_base = u64_to_user_ptr(rw->addr);
iov[0].iov_len = rw->len;
return 0;
}
if (rw->len != 1)
return -EINVAL;
#ifdef CONFIG_COMPAT
if (req->ctx->compat)
return io_compat_import(req, iov, issue_flags);
#endif
return __io_iov_buffer_select(req, iov, issue_flags);
}
static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
struct io_rw_state *s,
unsigned int issue_flags)
@ -374,7 +351,8 @@ static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
buf = u64_to_user_ptr(rw->addr);
sqe_len = rw->len;
if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE ||
(req->flags & REQ_F_BUFFER_SELECT)) {
if (io_do_buffer_select(req)) {
buf = io_buffer_select(req, &sqe_len, issue_flags);
if (!buf)
@ -390,14 +368,6 @@ static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
}
iovec = s->fast_iov;
if (req->flags & REQ_F_BUFFER_SELECT) {
ret = io_iov_buffer_select(req, iovec, issue_flags);
if (ret)
return ERR_PTR(ret);
iov_iter_init(iter, ddir, iovec, 1, iovec->iov_len);
return NULL;
}
ret = __import_iovec(ddir, buf, sqe_len, UIO_FASTIOV, &iovec, iter,
req->ctx->compat);
if (unlikely(ret < 0))