[PATCH 6.12 001/242] io_uring/kbuf: remove legacy kbuf bulk allocation

Greg Kroah-Hartman
2026-04-08T18:39:38Z

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

Commit 7919292a961421bfdb22f83c16657684c96076b3 upstream.

Legacy provided buffers are slow and discouraged in favour of the ring
variant. Remove the bulk allocation to keep it simpler as we don't care
about performance.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a064d70370e590efed8076e9501ae4cfc20fe0ca.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/kbuf.c | 30 +++++-------------------------
1 file changed, 5 insertions(+), 25 deletions(-)

--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -521,12 +521,9 @@ int io_provide_buffers_prep(struct io_ki
return 0;
}

-#define IO_BUFFER_ALLOC_BATCH 64
-
static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
{
- struct io_buffer *bufs[IO_BUFFER_ALLOC_BATCH];
- int allocated;
+ struct io_buffer *buf;

/*
* Completions that don't happen inline (eg not under uring_lock) will
@@ -544,27 +541,10 @@ static int io_refill_buffer_cache(struct
spin_unlock(&ctx->completion_lock);
}

- /*
- * No free buffers and no completion entries either. Allocate a new
- * batch of buffer entries and add those to our freelist.
- */
-
- allocated = kmem_cache_alloc_bulk(io_buf_cachep, GFP_KERNEL_ACCOUNT,
- ARRAY_SIZE(bufs), (void **) bufs);
- if (unlikely(!allocated)) {
- /*
- * Bulk alloc is all-or-nothing. If we fail to get a batch,
- * retry single alloc to be on the safe side.
- */
- bufs[0] = kmem_cache_alloc(io_buf_cachep, GFP_KERNEL);
- if (!bufs[0])
- return -ENOMEM;
- allocated = 1;
- }
-
- while (allocated)
- list_add_tail(&bufs[--allocated]->list, &ctx->io_buffers_cache);
-
+ buf = kmem_cache_alloc(io_buf_cachep, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+ list_add_tail(&buf->list, &ctx->io_buffers_cache);
return 0;
}