[PATCH v2 5/6] io_uring/zcrx: move zcrx region to struct io_zcrx_ifq

[Pavel Begunkov <asml.silence@gmail.com>]

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>
---
 include/linux/io_uring_types.h |  2 --
 io_uring/zcrx.c                | 20 ++++++++++++--------
 io_uring/zcrx.h                |  1 +
 3 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 3b467879bca8..06d722289fc5 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 652daff0eb8d..d56665fd103d 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -160,12 +160,11 @@ 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;
@@ -173,7 +172,10 @@ 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;
 }
@@ -334,9 +336,9 @@ 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,
@@ -428,7 +430,8 @@ 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);
@@ -444,7 +447,8 @@ 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 a183125e69f0..e58191d56249 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -38,6 +38,7 @@ struct io_zcrx_ifq {
 	struct net_device		*netdev;
 	netdevice_tracker		netdev_tracker;
 	spinlock_t			lock;
+	struct io_mapped_region		region;
 };
 
 #if defined(CONFIG_IO_URING_ZCRX)
-- 
2.48.1