This is a note to let you know that I've just added the patch titled
io_uring/kbuf: protect io_buffer_list teardown with a reference
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-kbuf-protect-io_buffer_list-teardown-with-a-reference.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6b69c4ab4f685327d9e10caf0d84217ba23a8c4b Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxxxxx>
Date: Fri, 15 Mar 2024 16:12:51 -0600
Subject: io_uring/kbuf: protect io_buffer_list teardown with a reference
From: Jens Axboe <axboe@xxxxxxxxx>
commit 6b69c4ab4f685327d9e10caf0d84217ba23a8c4b upstream.
No functional changes in this patch, just in preparation for being able
to keep the buffer list alive outside of the ctx->uring_lock.
Cc: stable@xxxxxxxxxxxxxxx # v6.4+
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/kbuf.c | 15 +++++++++++----
io_uring/kbuf.h | 2 ++
2 files changed, 13 insertions(+), 4 deletions(-)
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -61,6 +61,7 @@ static int io_buffer_add_list(struct io_
* always under the ->uring_lock, but the RCU lookup from mmap does.
*/
bl->bgid = bgid;
+ atomic_set(&bl->refs, 1);
return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
}
@@ -274,6 +275,14 @@ static int __io_remove_buffers(struct io
return i;
}
+static void io_put_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
+{
+ if (atomic_dec_and_test(&bl->refs)) {
+ __io_remove_buffers(ctx, bl, -1U);
+ kfree_rcu(bl, rcu);
+ }
+}
+
void io_destroy_buffers(struct io_ring_ctx *ctx)
{
struct io_buffer_list *bl;
@@ -283,8 +292,7 @@ void io_destroy_buffers(struct io_ring_c
xa_for_each(&ctx->io_bl_xa, index, bl) {
xa_erase(&ctx->io_bl_xa, bl->bgid);
- __io_remove_buffers(ctx, bl, -1U);
- kfree_rcu(bl, rcu);
+ io_put_bl(ctx, bl);
}
/*
@@ -689,9 +697,8 @@ int io_unregister_pbuf_ring(struct io_ri
if (!bl->is_mapped)
return -EINVAL;
- __io_remove_buffers(ctx, bl, -1U);
xa_erase(&ctx->io_bl_xa, bl->bgid);
- kfree_rcu(bl, rcu);
+ io_put_bl(ctx, bl);
return 0;
}
--- a/io_uring/kbuf.h
+++ b/io_uring/kbuf.h
@@ -25,6 +25,8 @@ struct io_buffer_list {
__u16 head;
__u16 mask;
+ atomic_t refs;
+
/* ring mapped provided buffers */
__u8 is_mapped;
/* ring mapped provided buffers, but mmap'ed by application */
Patches currently in stable-queue which might be from axboe@xxxxxxxxx are
queue-6.8/io_uring-rw-don-t-allow-multishot-reads-without-nowait-support.patch
queue-6.8/io_uring-use-private-workqueue-for-exit-work.patch
queue-6.8/io_uring-kbuf-protect-io_buffer_list-teardown-with-a-reference.patch
queue-6.8/io_uring-kbuf-hold-io_buffer_list-reference-over-mmap.patch
queue-6.8/io_uring-kbuf-get-rid-of-lower-bgid-lists.patch
queue-6.8/io_uring-kbuf-get-rid-of-bl-is_ready.patch
