[PATCH 5/8] io_uring/rsrc: consolidate node caching

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

We store one pre-allocated rsrc node in ->rsrc_backup_node, merge it
with ->rsrc_node_cache.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/linux/io_uring_types.h |  1 -
 io_uring/alloc_cache.h         |  5 +++++
 io_uring/io_uring.c            |  2 --
 io_uring/rsrc.c                | 20 +++++++++++---------
 4 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index fa621a508a01..40cab420b1bd 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -326,7 +326,6 @@ struct io_ring_ctx {
 	struct io_restriction		restrictions;
 
 	/* slow path rsrc auxilary data, used by update/register */
-	struct io_rsrc_node		*rsrc_backup_node;
 	struct io_mapped_ubuf		*dummy_ubuf;
 	struct io_rsrc_data		*file_data;
 	struct io_rsrc_data		*buf_data;
diff --git a/io_uring/alloc_cache.h b/io_uring/alloc_cache.h
index 851a527afb5e..241245cb54a6 100644
--- a/io_uring/alloc_cache.h
+++ b/io_uring/alloc_cache.h
@@ -23,6 +23,11 @@ static inline bool io_alloc_cache_put(struct io_alloc_cache *cache,
 	return false;
 }
 
+static inline bool io_alloc_cache_empty(struct io_alloc_cache *cache)
+{
+	return !cache->list.next;
+}
+
 static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache)
 {
 	if (cache->list.next) {
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index b171c26d331d..075bae8a2bb1 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2852,8 +2852,6 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	/* there are no registered resources left, nobody uses it */
 	if (ctx->rsrc_node)
 		io_rsrc_node_destroy(ctx, ctx->rsrc_node);
-	if (ctx->rsrc_backup_node)
-		io_rsrc_node_destroy(ctx, ctx->rsrc_backup_node);
 
 	WARN_ON_ONCE(!list_empty(&ctx->rsrc_ref_list));
 
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 24e4e2109549..73f9e10d9bf0 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -230,7 +230,7 @@ void io_rsrc_node_switch(struct io_ring_ctx *ctx,
 			 struct io_rsrc_data *data_to_kill)
 	__must_hold(&ctx->uring_lock)
 {
-	WARN_ON_ONCE(!ctx->rsrc_backup_node);
+	WARN_ON_ONCE(io_alloc_cache_empty(&ctx->rsrc_node_cache));
 	WARN_ON_ONCE(data_to_kill && !ctx->rsrc_node);
 
 	if (data_to_kill) {
@@ -245,18 +245,20 @@ void io_rsrc_node_switch(struct io_ring_ctx *ctx,
 		ctx->rsrc_node = NULL;
 	}
 
-	if (!ctx->rsrc_node) {
-		ctx->rsrc_node = ctx->rsrc_backup_node;
-		ctx->rsrc_backup_node = NULL;
-	}
+	if (!ctx->rsrc_node)
+		ctx->rsrc_node = io_rsrc_node_alloc(ctx);
 }
 
 int io_rsrc_node_switch_start(struct io_ring_ctx *ctx)
 {
-	if (ctx->rsrc_backup_node)
-		return 0;
-	ctx->rsrc_backup_node = io_rsrc_node_alloc(ctx);
-	return ctx->rsrc_backup_node ? 0 : -ENOMEM;
+	if (io_alloc_cache_empty(&ctx->rsrc_node_cache)) {
+		struct io_rsrc_node *node = kzalloc(sizeof(*node), GFP_KERNEL);
+
+		if (!node)
+			return -ENOMEM;
+		io_alloc_cache_put(&ctx->rsrc_node_cache, &node->cache);
+	}
+	return 0;
 }
 
 __cold static int io_rsrc_ref_quiesce(struct io_rsrc_data *data,
-- 
2.40.0