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, 9 deletions

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 6a63ec4b5445..1f6a82128b47 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -168,23 +168,16 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, u64 res2,
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_done);
 
-static void io_uring_cmd_init_once(void *obj)
-{
-	struct io_uring_cmd_data *data = obj;
-
-	data->op_data = NULL;
-}	
-
 static int io_uring_cmd_prep_setup(struct io_kiocb *req,
 				   const struct io_uring_sqe *sqe)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 	struct io_uring_cmd_data *cache;
 
-	cache = io_uring_alloc_async_data(&req->ctx->uring_cache, req,
-			io_uring_cmd_init_once);
+	cache = io_uring_alloc_async_data(&req->ctx->uring_cache, req);
 	if (!cache)
 		return -ENOMEM;
+	cache->op_data = NULL;
 
 	if (!(req->flags & REQ_F_FORCE_ASYNC)) {
 		/* defer memcpy until we need it */