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, 5 deletions

diff --git a/io_uring/uring_cmd.h b/io_uring/uring_cmd.h
index 477ea8865639..a361f98664d2 100644
--- a/io_uring/uring_cmd.h
+++ b/io_uring/uring_cmd.h
@@ -1,15 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 
 struct uring_cache {
-	union {
-		struct io_cache_entry cache;
-		struct io_uring_sqe sqes[2];
-	};
+	struct io_uring_sqe sqes[2];
 };
 
 int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags);
 int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
-void io_uring_cache_free(struct io_cache_entry *entry);
 
 bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
 				   struct task_struct *task, bool cancel_all);