[PATCH 6.12 003/242] io_uring/kbuf: simplify __io_put_kbuf

Greg Kroah-Hartman
2026-04-08T18:40:34Z

From: Pavel Begunkov <asml.silence@gmail.com>

Commit dc39fb1093ea33019f192c93b77b863282e10162 upstream.

As a preparation step remove an optimisation from __io_put_kbuf() trying
to use the locked cache. With that __io_put_kbuf_list() is only used
with ->io_buffers_comp, and we remove the explicit list argument.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1b7f1394ec4afc7f96b35a61f5992e27c49fd067.1738724373.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
io_uring/io_uring.c | 2 --
io_uring/kbuf.c | 26 +++-----------------------
io_uring/kbuf.h | 11 +++++------
3 files changed, 8 insertions(+), 31 deletions(-)

--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -385,9 +385,7 @@ static bool req_need_defer(struct io_kio
static void io_clean_op(struct io_kiocb *req)
{
if (req->flags & REQ_F_BUFFER_SELECTED) {
- spin_lock(&req->ctx->completion_lock);
io_kbuf_drop(req);
- spin_unlock(&req->ctx->completion_lock);
}

if (req->flags & REQ_F_NEED_CLEANUP) {
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -78,29 +78,9 @@ bool io_kbuf_recycle_legacy(struct io_ki

void __io_put_kbuf(struct io_kiocb *req, int len, unsigned issue_flags)
{
- /*
- * We can add this buffer back to two lists:
- *
- * 1) The io_buffers_cache list. This one is protected by the
- * ctx->uring_lock. If we already hold this lock, add back to this
- * list as we can grab it from issue as well.
- * 2) The io_buffers_comp list. This one is protected by the
- * ctx->completion_lock.
- *
- * We migrate buffers from the comp_list to the issue cache list
- * when we need one.
- */
- if (issue_flags & IO_URING_F_UNLOCKED) {
- struct io_ring_ctx *ctx = req->ctx;
-
- spin_lock(&ctx->completion_lock);
- __io_put_kbuf_list(req, len, &ctx->io_buffers_comp);
- spin_unlock(&ctx->completion_lock);
- } else {
- lockdep_assert_held(&req->ctx->uring_lock);
-
- __io_put_kbuf_list(req, len, &req->ctx->io_buffers_cache);
- }
+ spin_lock(&req->ctx->completion_lock);
+ __io_put_kbuf_list(req, len);
+ spin_unlock(&req->ctx->completion_lock);
}

static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
--- a/io_uring/kbuf.h
+++ b/io_uring/kbuf.h
@@ -171,27 +171,26 @@ static inline bool __io_put_kbuf_ring(st
return ret;
}

-static inline void __io_put_kbuf_list(struct io_kiocb *req, int len,
- struct list_head *list)
+static inline void __io_put_kbuf_list(struct io_kiocb *req, int len)
{
if (req->flags & REQ_F_BUFFER_RING) {
__io_put_kbuf_ring(req, len, 1);
} else {
req->buf_index = req->kbuf->bgid;
- list_add(&req->kbuf->list, list);
+ list_add(&req->kbuf->list, &req->ctx->io_buffers_comp);
req->flags &= ~REQ_F_BUFFER_SELECTED;
}
}

static inline void io_kbuf_drop(struct io_kiocb *req)
{
- lockdep_assert_held(&req->ctx->completion_lock);
-
if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
return;

+ spin_lock(&req->ctx->completion_lock);
/* len == 0 is fine here, non-ring will always drop all of it */
- __io_put_kbuf_list(req, 0, &req->ctx->io_buffers_comp);
+ __io_put_kbuf_list(req, 0);
+ spin_unlock(&req->ctx->completion_lock);
}

static inline unsigned int __io_put_kbufs(struct io_kiocb *req, int len,