From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sun, 20 Apr 2025 09:31:19 +0000 (+0100)
Subject: io_uring/zcrx: move zcrx region to struct io_zcrx_ifq
X-Git-Tag: v6.16-rc1~215^2~45
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=632b3186726984319e2337987de86a442407f30e;p=thirdparty%2Fkernel%2Flinux.git

io_uring/zcrx: move zcrx region to struct io_zcrx_ifq

Refill queue region is a part of zcrx and should stay in struct
io_zcrx_ifq. We can't have multiple queues without it, so move it there.

As a result there is no context global zcrx region anymore, and the
region is looked up together with its ifq. To protect a concurrent mmap
from seeing an inconsistent region we were protecting changes to
->zcrx_region with mmap_lock, but now it protect the publishing of the
ifq.

Reviewed-by: David Wei <dw@davidwei.uk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/24f1a728fc03d0166f16d099575457e10d9d90f2.1745141261.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 3b467879bca89..06d722289fc5a 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -448,8 +448,6 @@ struct io_ring_ctx {
 	struct io_mapped_region		ring_region;
 	/* used for optimised request parameter and wait argument passing  */
 	struct io_mapped_region		param_region;
-	/* just one zcrx per ring for now, will move to io_zcrx_ifq eventually */
-	struct io_mapped_region		zcrx_region;
 };
 
 /*
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index b7e65ae413b62..033284b695c7e 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -167,12 +167,11 @@ static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
 	if (size > rd->size)
 		return -EINVAL;
 
-	ret = io_create_region_mmap_safe(ifq->ctx, &ifq->ctx->zcrx_region, rd,
-					 IORING_MAP_OFF_ZCRX_REGION);
+	ret = io_create_region(ifq->ctx, &ifq->region, rd, IORING_MAP_OFF_ZCRX_REGION);
 	if (ret < 0)
 		return ret;
 
-	ptr = io_region_get_ptr(&ifq->ctx->zcrx_region);
+	ptr = io_region_get_ptr(&ifq->region);
 	ifq->rq_ring = (struct io_uring *)ptr;
 	ifq->rqes = (struct io_uring_zcrx_rqe *)(ptr + off);
 	return 0;
@@ -180,7 +179,10 @@ static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
 
 static void io_free_rbuf_ring(struct io_zcrx_ifq *ifq)
 {
-	io_free_region(ifq->ctx, &ifq->ctx->zcrx_region);
+	if (WARN_ON_ONCE(ifq->ctx->ifq))
+		return;
+
+	io_free_region(ifq->ctx, &ifq->region);
 	ifq->rq_ring = NULL;
 	ifq->rqes = NULL;
 }
@@ -343,9 +345,9 @@ struct io_mapped_region *io_zcrx_get_region(struct io_ring_ctx *ctx,
 {
 	lockdep_assert_held(&ctx->mmap_lock);
 
-	if (id != 0)
+	if (id != 0 || !ctx->ifq)
 		return NULL;
-	return &ctx->zcrx_region;
+	return &ctx->ifq->region;
 }
 
 int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
@@ -433,7 +435,8 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		ret = -EFAULT;
 		goto err;
 	}
-	ctx->ifq = ifq;
+	scoped_guard(mutex, &ctx->mmap_lock)
+		ctx->ifq = ifq;
 	return 0;
 err:
 	io_zcrx_ifq_free(ifq);
@@ -449,7 +452,8 @@ void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)
 	if (!ifq)
 		return;
 
-	ctx->ifq = NULL;
+	scoped_guard(mutex, &ctx->mmap_lock)
+		ctx->ifq = NULL;
 	io_zcrx_ifq_free(ifq);
 }
 
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 43134e5c92133..e3c7c4e647f11 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -39,6 +39,7 @@ struct io_zcrx_ifq {
 	netdevice_tracker		netdev_tracker;
 	spinlock_t			lock;
 	struct mutex			dma_lock;
+	struct io_mapped_region		region;
 };
 
 #if defined(CONFIG_IO_URING_ZCRX)