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, 12 insertions, 18 deletions

diff --git a/io_uring/futex.c b/io_uring/futex.c
index 792a03df58de..914848f46beb 100644
--- a/io_uring/futex.c
+++ b/io_uring/futex.c
@@ -9,7 +9,7 @@
 
 #include "../kernel/futex/futex.h"
 #include "io_uring.h"
-#include "rsrc.h"
+#include "alloc_cache.h"
 #include "futex.h"
 
 struct io_futex {
@@ -27,27 +27,21 @@ struct io_futex {
 };
 
 struct io_futex_data {
-	union {
-		struct futex_q		q;
-		struct io_cache_entry	cache;
-	};
+	struct futex_q	q;
 	struct io_kiocb	*req;
 };
 
-void io_futex_cache_init(struct io_ring_ctx *ctx)
-{
-	io_alloc_cache_init(&ctx->futex_cache, IO_NODE_ALLOC_CACHE_MAX,
-				sizeof(struct io_futex_data));
-}
+#define IO_FUTEX_ALLOC_CACHE_MAX	32
 
-static void io_futex_cache_entry_free(struct io_cache_entry *entry)
+bool io_futex_cache_init(struct io_ring_ctx *ctx)
 {
-	kfree(container_of(entry, struct io_futex_data, cache));
+	return io_alloc_cache_init(&ctx->futex_cache, IO_FUTEX_ALLOC_CACHE_MAX,
+				sizeof(struct io_futex_data));
 }
 
 void io_futex_cache_free(struct io_ring_ctx *ctx)
 {
-	io_alloc_cache_free(&ctx->futex_cache, io_futex_cache_entry_free);
+	io_alloc_cache_free(&ctx->futex_cache, kfree);
 }
 
 static void __io_futex_complete(struct io_kiocb *req, struct io_tw_state *ts)
@@ -63,7 +57,7 @@ static void io_futex_complete(struct io_kiocb *req, struct io_tw_state *ts)
 	struct io_ring_ctx *ctx = req->ctx;
 
 	io_tw_lock(ctx, ts);
-	if (!io_alloc_cache_put(&ctx->futex_cache, &ifd->cache))
+	if (!io_alloc_cache_put(&ctx->futex_cache, ifd))
 		kfree(ifd);
 	__io_futex_complete(req, ts);
 }
@@ -259,11 +253,11 @@ static void io_futex_wake_fn(struct wake_q_head *wake_q, struct futex_q *q)
 
 static struct io_futex_data *io_alloc_ifd(struct io_ring_ctx *ctx)
 {
-	struct io_cache_entry *entry;
+	struct io_futex_data *ifd;
 
-	entry = io_alloc_cache_get(&ctx->futex_cache);
-	if (entry)
-		return container_of(entry, struct io_futex_data, cache);
+	ifd = io_alloc_cache_get(&ctx->futex_cache);
+	if (ifd)
+		return ifd;
 
 	return kmalloc(sizeof(struct io_futex_data), GFP_NOWAIT);
 }