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, 22 deletions

diff --git a/io_uring/net.c b/io_uring/net.c
index 85f55fbc25c9..41eef286f8b9 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -137,7 +137,6 @@ static void io_netmsg_iovec_free(struct io_async_msghdr *kmsg)
 static void io_netmsg_recycle(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_async_msghdr *hdr = req->async_data;
-	struct iovec *iov;
 
 	/* can't recycle, ensure we free the iovec if we have one */
 	if (unlikely(issue_flags & IO_URING_F_UNLOCKED)) {
@@ -146,39 +145,25 @@ static void io_netmsg_recycle(struct io_kiocb *req, unsigned int issue_flags)
 	}
 
 	/* Let normal cleanup path reap it if we fail adding to the cache */
-	iov = hdr->free_iov;
+	io_alloc_cache_kasan(&hdr->free_iov, &hdr->free_iov_nr);
 	if (io_alloc_cache_put(&req->ctx->netmsg_cache, hdr)) {
-		if (iov)
-			kasan_mempool_poison_object(iov);
 		req->async_data = NULL;
 		req->flags &= ~REQ_F_ASYNC_DATA;
 	}
 }
 
-static void io_msg_async_data_init(void *obj)
-{
-	struct io_async_msghdr *hdr = (struct io_async_msghdr *)obj;
-
-	hdr->free_iov = NULL;
-	hdr->free_iov_nr = 0;
-}
-
 static struct io_async_msghdr *io_msg_alloc_async(struct io_kiocb *req)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_async_msghdr *hdr;
 
-	hdr = io_uring_alloc_async_data(&ctx->netmsg_cache, req,
-					io_msg_async_data_init);
+	hdr = io_uring_alloc_async_data(&ctx->netmsg_cache, req);
 	if (!hdr)
 		return NULL;
 
 	/* If the async data was cached, we might have an iov cached inside. */
-	if (hdr->free_iov) {
-		kasan_mempool_unpoison_object(hdr->free_iov,
-					      hdr->free_iov_nr * sizeof(struct iovec));
+	if (hdr->free_iov)
 		req->flags |= REQ_F_NEED_CLEANUP;
-	}
 	return hdr;
 }
 
@@ -1813,11 +1798,10 @@ void io_netmsg_cache_free(const void *entry)
 {
 	struct io_async_msghdr *kmsg = (struct io_async_msghdr *) entry;
 
-	if (kmsg->free_iov) {
-		kasan_mempool_unpoison_object(kmsg->free_iov,
-				kmsg->free_iov_nr * sizeof(struct iovec));
+#if !defined(CONFIG_KASAN)
+	if (kmsg->free_iov)
 		io_netmsg_iovec_free(kmsg);
-	}
+#endif
 	kfree(kmsg);
 }
 #endif