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, 6 insertions, 21 deletions

diff --git a/io_uring/rw.c b/io_uring/rw.c
index a9a2733be842..991ecfbea88e 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -158,16 +158,13 @@ static void io_rw_iovec_free(struct io_async_rw *rw)
 static void io_rw_recycle(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_async_rw *rw = req->async_data;
-	struct iovec *iov;
 
 	if (unlikely(issue_flags & IO_URING_F_UNLOCKED)) {
 		io_rw_iovec_free(rw);
 		return;
 	}
-	iov = rw->free_iovec;
+	io_alloc_cache_kasan(&rw->free_iovec, &rw->free_iov_nr);
 	if (io_alloc_cache_put(&req->ctx->rw_cache, rw)) {
-		if (iov)
-			kasan_mempool_poison_object(iov);
 		req->async_data = NULL;
 		req->flags &= ~REQ_F_ASYNC_DATA;
 	}
@@ -208,27 +205,16 @@ static void io_req_rw_cleanup(struct io_kiocb *req, unsigned int issue_flags)
 	}
 }
 
-static void io_rw_async_data_init(void *obj)
-{
-	struct io_async_rw *rw = (struct io_async_rw *)obj;
-
-	rw->free_iovec = NULL;
-	rw->bytes_done = 0;
-}
-
 static int io_rw_alloc_async(struct io_kiocb *req)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_async_rw *rw;
 
-	rw = io_uring_alloc_async_data(&ctx->rw_cache, req, io_rw_async_data_init);
+	rw = io_uring_alloc_async_data(&ctx->rw_cache, req);
 	if (!rw)
 		return -ENOMEM;
-	if (rw->free_iovec) {
-		kasan_mempool_unpoison_object(rw->free_iovec,
-					      rw->free_iov_nr * sizeof(struct iovec));
+	if (rw->free_iovec)
 		req->flags |= REQ_F_NEED_CLEANUP;
-	}
 	rw->bytes_done = 0;
 	return 0;
 }
@@ -1323,10 +1309,9 @@ void io_rw_cache_free(const void *entry)
 {
 	struct io_async_rw *rw = (struct io_async_rw *) entry;
 
-	if (rw->free_iovec) {
-		kasan_mempool_unpoison_object(rw->free_iovec,
-				rw->free_iov_nr * sizeof(struct iovec));
+#if !defined(CONFIG_KASAN)
+	if (rw->free_iovec)
 		io_rw_iovec_free(rw);
-	}
+#endif
 	kfree(rw);
 }