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From: Jens Axboe <[email protected]>
To: [email protected]
Cc: Jens Axboe <[email protected]>
Subject: [PATCH 4/6] io_uring/kbuf: protect io_buffer_list teardown with a reference
Date: Thu, 21 Mar 2024 08:44:59 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

No functional changes in this patch, just in preparation for being able
to keep the buffer list alive outside of the ctx->uring_lock.

Signed-off-by: Jens Axboe <[email protected]>
---
 io_uring/kbuf.c | 15 +++++++++++----
 io_uring/kbuf.h |  2 ++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 72c15dde34d3..206f4d352e15 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -62,6 +62,7 @@ static int io_buffer_add_list(struct io_ring_ctx *ctx,
 	 * 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));
 }
 
@@ -259,6 +260,14 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx,
 	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;
@@ -268,8 +277,7 @@ void io_destroy_buffers(struct io_ring_ctx *ctx)
 
 	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);
 	}
 
 	/*
@@ -671,9 +679,8 @@ int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 	if (!bl->is_buf_ring)
 		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;
 }
 
diff --git a/io_uring/kbuf.h b/io_uring/kbuf.h
index fdbb10449513..8b868a1744e2 100644
--- 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_buf_ring;
 	/* ring mapped provided buffers, but mmap'ed by application */
-- 
2.43.0


  parent reply	other threads:[~2024-03-21 14:48 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-21 14:44 [PATCHSET 0/6] Switch kbuf mappings to vm_insert_pages() Jens Axboe
2024-03-21 14:44 ` [PATCH 1/6] io_uring/kbuf: get rid of lower BGID lists Jens Axboe
2024-03-21 14:44 ` [PATCH 2/6] io_uring/kbuf: get rid of bl->is_ready Jens Axboe
2024-03-21 14:44 ` [PATCH 3/6] io_uring/kbuf: vmap pinned buffer ring Jens Axboe
2024-03-21 14:44 ` Jens Axboe [this message]
2024-03-21 14:45 ` [PATCH 5/6] mm: add nommu variant of vm_insert_pages() Jens Axboe
2024-03-21 14:45 ` [PATCH 6/6] io_uring/kbuf: use vm_insert_pages() for mmap'ed pbuf ring Jens Axboe

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