io_uring/alloc_cache: switch to array based caching

Currently lists are being used to manage this, but best practice is
usually to have these in an array instead as that it cheaper to manage.

Outside of that detail, games are also played with KASAN as the list
is inside the cached entry itself.

Finally, all users of this need a struct io_cache_entry embedded in
their struct, which is union'ized with something else in there that
isn't used across the free -> realloc cycle.

Get rid of all of that, and simply have it be an array. This will not
change the memory used, as we're just trading an 8-byte member entry
for the per-elem array size.

This reduces the overhead of the recycled allocations, and it reduces
the amount of code code needed to support recycling to about half of
what it currently is.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 6 deletions

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 4818b79231dd..7b8a056f98ed 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -13,6 +13,7 @@
 #include <uapi/linux/io_uring.h>
 
 #include "io_uring.h"
+#include "alloc_cache.h"
 #include "openclose.h"
 #include "rsrc.h"
 
@@ -169,7 +170,7 @@ static void io_rsrc_put_work(struct io_rsrc_node *node)
 
 void io_rsrc_node_destroy(struct io_ring_ctx *ctx, struct io_rsrc_node *node)
 {
-	if (!io_alloc_cache_put(&ctx->rsrc_node_cache, &node->cache))
+	if (!io_alloc_cache_put(&ctx->rsrc_node_cache, node))
 		kfree(node);
 }
 
@@ -197,12 +198,9 @@ void io_rsrc_node_ref_zero(struct io_rsrc_node *node)
 struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx)
 {
 	struct io_rsrc_node *ref_node;
-	struct io_cache_entry *entry;
 
-	entry = io_alloc_cache_get(&ctx->rsrc_node_cache);
-	if (entry) {
-		ref_node = container_of(entry, struct io_rsrc_node, cache);
-	} else {
+	ref_node = io_alloc_cache_get(&ctx->rsrc_node_cache);
+	if (!ref_node) {
 		ref_node = kzalloc(sizeof(*ref_node), GFP_KERNEL);
 		if (!ref_node)
 			return NULL;