From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5CD90C001B0 for ; Wed, 19 Jul 2023 20:39:41 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qMDvA-0005zQ-Lg; Wed, 19 Jul 2023 16:37:16 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qMDv9-0005yI-O8 for qemu-devel@nongnu.org; Wed, 19 Jul 2023 16:37:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qMDv6-0001oq-NQ for qemu-devel@nongnu.org; Wed, 19 Jul 2023 16:37:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689799032; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Chmbko4sWhMG09e5JGonEJeIeKSnNGzYh9pj24p9T78=; b=MW25RSI2ByawybqvrERoUjW/G1n2JrYil/jTJTDbtpGyyO66uBSVha8V0bW2hD6AVatnbh ScWj4lcaKVjSDxGqL6q65qwhCVGWlRyZOohsqF4/HovC1W6QJe/4Uxh30SLZNdXYY+lgam YBBRc37q/23Bqc0ji3yiiD38VeBrJNU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-620-4Akn8B84PS2hKXYGMEUCsA-1; Wed, 19 Jul 2023 16:37:10 -0400 X-MC-Unique: 4Akn8B84PS2hKXYGMEUCsA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 582408F1846; Wed, 19 Jul 2023 20:37:10 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.192]) by smtp.corp.redhat.com (Postfix) with ESMTP id D76294CD0F8; Wed, 19 Jul 2023 20:37:09 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: Vladimir Sementsov-Ogievskiy , Kevin Wolf , Hanna Reitz , qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PULL 12/14] nbd/client: Simplify cookie vs. index computation Date: Wed, 19 Jul 2023 15:27:49 -0500 Message-ID: <20230719202736.2675295-28-eblake@redhat.com> In-Reply-To: <20230719202736.2675295-16-eblake@redhat.com> References: <20230719202736.2675295-16-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Our code relies on a sentinel cookie value of zero for deciding when a packet has been handled, as well as relying on array indices between 0 and MAX_NBD_REQUESTS-1 for dereferencing purposes. As long as we can symmetrically convert between two forms, there is no reason to go with the odd choice of using XOR with a random pointer, when we can instead simplify the mappings with a mere offset of 1. Using ((uint64_t)-1) as the sentinel instead of NULL such that the two macros could be entirely eliminated might also be possible, but would require a more careful audit to find places where we currently rely on zero-initialization to be interpreted as the sentinel value, so I did not pursue that course. Signed-off-by: Eric Blake Message-ID: <20230608135653.2918540-7-eblake@redhat.com> [eblake: enhance commit message] Reviewed-by: Vladimir Sementsov-Ogievskiy --- block/nbd.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/block/nbd.c b/block/nbd.c index be3c46c6fee..5322e66166c 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -50,8 +50,8 @@ #define EN_OPTSTR ":exportname=" #define MAX_NBD_REQUESTS 16 -#define COOKIE_TO_INDEX(bs, cookie) ((cookie) ^ (uint64_t)(intptr_t)(bs)) -#define INDEX_TO_COOKIE(bs, index) ((index) ^ (uint64_t)(intptr_t)(bs)) +#define COOKIE_TO_INDEX(cookie) ((cookie) - 1) +#define INDEX_TO_COOKIE(index) ((index) + 1) typedef struct { Coroutine *coroutine; @@ -420,7 +420,7 @@ static void coroutine_fn GRAPH_RDLOCK nbd_reconnect_attempt(BDRVNBDState *s) static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t cookie) { int ret; - uint64_t ind = COOKIE_TO_INDEX(s, cookie), ind2; + uint64_t ind = COOKIE_TO_INDEX(cookie), ind2; QEMU_LOCK_GUARD(&s->receive_mutex); while (true) { @@ -435,7 +435,7 @@ static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t cookie) * woken by whoever set s->reply.cookie (or never wait in this * yield). So, we should not wake it here. */ - ind2 = COOKIE_TO_INDEX(s, s->reply.cookie); + ind2 = COOKIE_TO_INDEX(s->reply.cookie); assert(!s->requests[ind2].receiving); s->requests[ind].receiving = true; @@ -468,7 +468,7 @@ static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t cookie) nbd_channel_error(s, -EINVAL); return -EINVAL; } - ind2 = COOKIE_TO_INDEX(s, s->reply.cookie); + ind2 = COOKIE_TO_INDEX(s->reply.cookie); if (ind2 >= MAX_NBD_REQUESTS || !s->requests[ind2].coroutine) { nbd_channel_error(s, -EINVAL); return -EINVAL; @@ -519,7 +519,7 @@ nbd_co_send_request(BlockDriverState *bs, NBDRequest *request, qemu_mutex_unlock(&s->requests_lock); qemu_co_mutex_lock(&s->send_mutex); - request->cookie = INDEX_TO_COOKIE(s, i); + request->cookie = INDEX_TO_COOKIE(i); assert(s->ioc); @@ -832,7 +832,7 @@ static coroutine_fn int nbd_co_do_receive_one_chunk( int *request_ret, QEMUIOVector *qiov, void **payload, Error **errp) { int ret; - int i = COOKIE_TO_INDEX(s, cookie); + int i = COOKIE_TO_INDEX(cookie); void *local_payload = NULL; NBDStructuredReplyChunk *chunk; @@ -1038,7 +1038,7 @@ static bool coroutine_fn nbd_reply_chunk_iter_receive(BDRVNBDState *s, break_loop: qemu_mutex_lock(&s->requests_lock); - s->requests[COOKIE_TO_INDEX(s, cookie)].coroutine = NULL; + s->requests[COOKIE_TO_INDEX(cookie)].coroutine = NULL; s->in_flight--; qemu_co_queue_next(&s->free_sema); qemu_mutex_unlock(&s->requests_lock); -- 2.41.0