io_uring: get rid of alloc cache init_once handling

init_once is called when an object doesn't come from the cache, and
hence needs initial clearing of certain members. While the whole
struct could get cleared by memset() in that case, a few of the cache
members are large enough that this may cause unnecessary overhead if
the caches used aren't large enough to satisfy the workload. For those
cases, some churn of kmalloc+kfree is to be expected.

Ensure that the 3 users that need clearing put the members they need
cleared at the start of the struct, and wrap the rest of the struct in
a struct group so the offset is known.

While at it, improve the interaction with KASAN such that when/if
KASAN writes to members inside the struct that should be retained over
caching, it won't trip over itself. For rw and net, the retaining of
the iovec over caching is disabled if KASAN is enabled. A helper will
free and clear those members in that case.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/io_uring/futex.c b/io_uring/futex.c
index 30139cc150f2..3159a2b7eeca 100644
--- a/io_uring/futex.c
+++ b/io_uring/futex.c
@@ -36,7 +36,7 @@ struct io_futex_data {
 bool io_futex_cache_init(struct io_ring_ctx *ctx)
 {
 	return io_alloc_cache_init(&ctx->futex_cache, IO_FUTEX_ALLOC_CACHE_MAX,
-				sizeof(struct io_futex_data));
+				sizeof(struct io_futex_data), 0);
 }
 
 void io_futex_cache_free(struct io_ring_ctx *ctx)
@@ -320,7 +320,7 @@ int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags)
 	}
 
 	io_ring_submit_lock(ctx, issue_flags);
-	ifd = io_cache_alloc(&ctx->futex_cache, GFP_NOWAIT, NULL);
+	ifd = io_cache_alloc(&ctx->futex_cache, GFP_NOWAIT);
 	if (!ifd) {
 		ret = -ENOMEM;
 		goto done_unlock;