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, 1 insertions, 6 deletions

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index e21000238954..83c079a707f8 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -2,8 +2,6 @@
 #ifndef IOU_RSRC_H
 #define IOU_RSRC_H
 
-#include "alloc_cache.h"
-
 #define IO_NODE_ALLOC_CACHE_MAX 32
 
 #define IO_RSRC_TAG_TABLE_SHIFT	(PAGE_SHIFT - 3)
@@ -36,10 +34,7 @@ struct io_rsrc_data {
 };
 
 struct io_rsrc_node {
-	union {
-		struct io_cache_entry		cache;
-		struct io_ring_ctx		*ctx;
-	};
+	struct io_ring_ctx		*ctx;
 	int				refs;
 	bool				empty;
 	u16				type;