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io_uring/kbuf: propagate BUF_MORE through early buffer commit path

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When io_should_commit() returns true (eg for non-pollable files), buffer
commit happens at buffer selection time and sel->buf_list is set to
NULL. When __io_put_kbufs() generates CQE flags at completion time, it
calls __io_put_kbuf_ring() which finds a NULL buffer_list and hence
cannot determine whether the buffer was consumed or not. This means that
IORING_CQE_F_BUF_MORE is never set for non-pollable input with
incrementally consumed buffers.

Likewise for io_buffers_select(), which always commits upfront and
discards the return value of io_kbuf_commit().

Add REQ_F_BUF_MORE to store the result of io_kbuf_commit() during early
commit. Then __io_put_kbuf_ring() can check this flag and set
IORING_F_BUF_MORE accordingy.

Reported-by: Martin Michaelis <code@mgjm.de>
Cc: stable@vger.kernel.org
Fixes: ae98dbf43d ("io_uring/kbuf: add support for incremental buffer consumption")
Link: https://github.com/axboe/liburing/issues/1553
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2026-03-19 14:29:20 -06:00
parent 3ecd3e0314
commit 418eab7a6f
2 changed files with 10 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/io_uring_types.h
View File

@@ -541,6 +541,7 @@ enum {
REQ_F_BL_NO_RECYCLE_BIT,
REQ_F_BUFFERS_COMMIT_BIT,
REQ_F_BUF_NODE_BIT,
REQ_F_BUF_MORE_BIT,
REQ_F_HAS_METADATA_BIT,
REQ_F_IMPORT_BUFFER_BIT,
REQ_F_SQE_COPIED_BIT,
@@ -626,6 +627,8 @@ enum {
REQ_F_BUFFERS_COMMIT = IO_REQ_FLAG(REQ_F_BUFFERS_COMMIT_BIT),
/* buf node is valid */
REQ_F_BUF_NODE = IO_REQ_FLAG(REQ_F_BUF_NODE_BIT),
/* incremental buffer consumption, more space available */
REQ_F_BUF_MORE = IO_REQ_FLAG(REQ_F_BUF_MORE_BIT),
/* request has read/write metadata assigned */
REQ_F_HAS_METADATA = IO_REQ_FLAG(REQ_F_HAS_METADATA_BIT),
/*

10
io_uring/kbuf.c
View File

@@ -216,7 +216,8 @@ static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len,
sel.addr = u64_to_user_ptr(READ_ONCE(buf->addr));
if (io_should_commit(req, issue_flags)) {
io_kbuf_commit(req, sel.buf_list, *len, 1);
if (!io_kbuf_commit(req, sel.buf_list, *len, 1))
req->flags |= REQ_F_BUF_MORE;
sel.buf_list = NULL;
}
return sel;
@@ -349,7 +350,8 @@ int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
*/
if (ret > 0) {
req->flags |= REQ_F_BUFFERS_COMMIT | REQ_F_BL_NO_RECYCLE;
io_kbuf_commit(req, sel->buf_list, arg->out_len, ret);
if (!io_kbuf_commit(req, sel->buf_list, arg->out_len, ret))
req->flags |= REQ_F_BUF_MORE;
}
} else {
ret = io_provided_buffers_select(req, &arg->out_len, sel->buf_list, arg->iovs);
@@ -395,8 +397,10 @@ static inline bool __io_put_kbuf_ring(struct io_kiocb *req,
if (bl)
ret = io_kbuf_commit(req, bl, len, nr);
if (ret && (req->flags & REQ_F_BUF_MORE))
ret = false;
req->flags &= ~REQ_F_BUFFER_RING;
req->flags &= ~(REQ_F_BUFFER_RING | REQ_F_BUF_MORE);
return ret;
}