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, 5 insertions, 13 deletions

diff --git a/io_uring/net.h b/io_uring/net.h
index b47b43ec6459..0eb1c1920fc9 100644
--- a/io_uring/net.h
+++ b/io_uring/net.h
@@ -3,23 +3,15 @@
 #include <linux/net.h>
 #include <linux/uio.h>
 
-#include "alloc_cache.h"
-
 struct io_async_msghdr {
 #if defined(CONFIG_NET)
-	union {
-		struct iovec			fast_iov;
-		struct {
-			struct io_cache_entry	cache;
-			/* entry size of ->free_iov, if valid */
-			int			free_iov_nr;
-		};
-	};
+	struct iovec			fast_iov;
 	/* points to an allocated iov, if NULL we use fast_iov instead */
 	struct iovec			*free_iov;
+	int				free_iov_nr;
+	int				namelen;
 	__kernel_size_t			controllen;
 	__kernel_size_t			payloadlen;
-	int				namelen;
 	struct sockaddr __user		*uaddr;
 	struct msghdr			msg;
 	struct sockaddr_storage		addr;
@@ -57,9 +49,9 @@ int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags);
 int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 void io_send_zc_cleanup(struct io_kiocb *req);
 
-void io_netmsg_cache_free(struct io_cache_entry *entry);
+void io_netmsg_cache_free(const void *entry);
 #else
-static inline void io_netmsg_cache_free(struct io_cache_entry *entry)
+static inline void io_netmsg_cache_free(const void *entry)
 {
 }
 #endif