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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8BB1FC25B0C for ; Tue, 9 Aug 2022 16:37:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245173AbiHIQhI (ORCPT ); Tue, 9 Aug 2022 12:37:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245186AbiHIQgq (ORCPT ); Tue, 9 Aug 2022 12:36:46 -0400 Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C5291D7; Tue, 9 Aug 2022 09:36:45 -0700 (PDT) Received: by mail-wr1-x42b.google.com with SMTP id n4so13160461wrp.10; Tue, 09 Aug 2022 09:36:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc; bh=Ok5+N/ROSsdYONZgRo7NN1XD5pWHK7Ij0qh3WOIp4Hk=; b=oKtlwHul5j/zPHGlStukJ7puPsBguip4EroHiSwJj69SbsyIQOpOT70cl5OMzYVAXe I+HxbGGO4NqFB35SbGR5zgsEBBzKNtYkYGEe7q7bJYbZUEPvBQ1UT9KAtBEqtqK/hnaG ShUgVOUKcGhnmAHCL5q2o2p+ertnx/8x7UVBbQP+7aVJ50ykQ/The/m16DuqZ1ALEuEl t4Sr15Ng/WVy/KuWppQsFAa81SPVCdacWM4WxUYABmGAhmE/ren06b63cJElTfdqr+zI mqCtbaYP+kd1Q/vgmINgk3RKqjKqoc+MoIMS8RTP0J+a740hCjtCDt0GtetWe4+1ZhWr TBZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc; bh=Ok5+N/ROSsdYONZgRo7NN1XD5pWHK7Ij0qh3WOIp4Hk=; b=xHG2x1+Y320tjVjt1q19yUW/32avgNbN2tDxooOZmne0hyHw9BpqKVlx883623gPPs 9UgquMwEht0P411ka7LfuW4vZZy4Z+f65U1uWi9Mj+PIw33pMMSB/+R+q3XA5gITO27D nBDYxmxQ8LA0u2NouFZchhadOsMNh7aM2A1TczvAxj6zCqZSaP19Qs3mCe95E4RTJ2hp quAro/RJmIbmRFVX+nO3V6yv6BOu3Y4fNzrrq150Syv+F8lx+juAo5zBrDJkfE9YV3pp whBas2mOPzDyi+vwKVV3Un5yuC0C+8Q4FrFcAJnm/+7iaDhhESinrK6wQsbPL1n/uaDL ctOQ== X-Gm-Message-State: ACgBeo0gFZ7QtDZ2+ojgNuqOsLsLnF0DIx17vEZQmUyyTrZjlIkBnXGN gD2qrLyB1OslDVrdlntLNyCbRFsHKrGhSA== X-Google-Smtp-Source: AA6agR6/nHRlqGWl2s71vXeZAAz1IiObS2iTo4xTRzVR/0nfk3Jy9qj99Lp4kxI2Gj1WaUJ27p/TBQ== X-Received: by 2002:adf:de0f:0:b0:21e:ead4:23f5 with SMTP id b15-20020adfde0f000000b0021eead423f5mr14580915wrm.641.1660063003709; Tue, 09 Aug 2022 09:36:43 -0700 (PDT) Received: from localhost.localdomain ([46.248.82.114]) by smtp.gmail.com with ESMTPSA id a7-20020a056000100700b0021f0c0c62d1sm13856980wrx.13.2022.08.09.09.36.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Aug 2022 09:36:43 -0700 (PDT) From: Uros Bizjak To: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Chris Mason , Josef Bacik , David Sterba Subject: [PATCH] fs/btrfs: Use atomic_try_cmpxchg in free_extent_buffer Date: Tue, 9 Aug 2022 18:36:33 +0200 Message-Id: <20220809163633.8255-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use `atomic_try_cmpxchg(ptr, &old, new)` instead of `atomic_cmpxchg(ptr, old, new) == old` in free_extent_buffer. This has two benefits: - The x86 cmpxchg instruction returns success in the ZF flag, so this change saves a compare after cmpxchg, as well as a related move instruction in the front of cmpxchg. - atomic_try_cmpxchg implicitly assigns the *ptr value to &old when cmpxchg fails, enabling further code simplifications. This patch has no functional change. Cc: Chris Mason Cc: Josef Bacik Cc: David Sterba Signed-off-by: Uros Bizjak --- fs/btrfs/extent_io.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index bfae67c593c5..15ff196cbd6d 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -6328,18 +6328,16 @@ static int release_extent_buffer(struct extent_buffer *eb) void free_extent_buffer(struct extent_buffer *eb) { int refs; - int old; if (!eb) return; + refs = atomic_read(&eb->refs); while (1) { - refs = atomic_read(&eb->refs); if ((!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs <= 3) || (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs == 1)) break; - old = atomic_cmpxchg(&eb->refs, refs, refs - 1); - if (old == refs) + if (atomic_try_cmpxchg(&eb->refs, &refs, refs - 1)) return; } -- 2.37.1