From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BB0741F09BF for ; Thu, 18 Sep 2025 09:52:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758189181; cv=none; b=W+QgK30HO06mU5QJ0tVK70a6FolCdhJPc3pG76ER2M9y4nrXB9zbpaKN3WRv0c/8m7zKFqzYrFHR5Jcznmw1agG88eS/KZAsJol2PcPhPdHseZ9mo5hwB05KfEz4M8ZNkqz+AoVZGVvDXfxvy6Kd8oyRwNwa5V4DuRym1+tI8Dk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758189181; c=relaxed/simple; bh=9NUcHiuwJ7yy7eIocMusuxX8hrBc3RhlUO2hxypoQxw=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=TSX4G3+d4cKIasHq+vFD2UsZzTqIo7yHzEN8kmaedEx3rZo+PW1Z+MOQJNiVis11qnaZv7DSfR9+JY8FMjTtp+Eyzo8RsxHuuWGjwLpq8k0pk98aaitzNK0gKf+7dlK66UjezQbdenlEseFA3EUw2YYTHXt1h2sFWA3bwoctRow= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=hEz2t9aX; arc=none smtp.client-ip=209.85.128.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="hEz2t9aX" Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-4619eb18311so4931465e9.1 for ; Thu, 18 Sep 2025 02:52:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1758189178; x=1758793978; darn=vger.kernel.org; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :from:to:cc:subject:date:message-id:reply-to; bh=xrCiUL75bZCAw4+y+WgmkA8zlr1SQwxLhmhWl+htlwk=; b=hEz2t9aXKEhir5Nk+ChxtrHLhkKTvBCvU8rvrYUqU9/elQhInakzHeH1I0/E/AQ/5s kyNqv+dia2t4sN1VM/p1pScq1GP/AOTaYGpY1ot32zt+YVFevgXxLCR/Jd74vZB1eJUH ritJ/aCGZt8wq9mi9FaLkP75Wdcu5YDK4QCTrUXiSRAJRGbKlsTAUBOB3K02U7e2Idlo +OUkATFJ0usreNE4gQp683D+zFQOAERQP+vaqf45poWsgmCt1NxFxGeRrL1+OVebBsCj n95uh3SWMw1T8+xKfTvQacb0b9fOm/6kcyvNmCVTxpgyGITWX3L2hlLnMe0dg0zOf5Oc 5egQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758189178; x=1758793978; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=xrCiUL75bZCAw4+y+WgmkA8zlr1SQwxLhmhWl+htlwk=; b=SqnVFreCB/C5WBhHwKt/8SNRyH5wEBzcC0MOF5yGyh6u4c4ZNLMuhlvHCymKkwQpOv z1rk/e3aB7bjMreBT9VPaTrLJKXR2jFFyVkjnhzKcKruDHsiClIlkTYQrlrJiMo3US89 JB3wxSI7vymsn+elhJ+lWyObY6MlWndS+XjNDHHqjnJLWp/MldxYI0qCRnFEJq+4mZww IRkJwXaL7bjcQ36FPtzTH2alMkdZj/YFktc1mNFfPyM81FOTZrJz/umAUW/x+KA8ei0w aKNkvAvfzlEd+27wY7Y5rxYJwRiSJRtMwFNPJTtIucTyQInkcJ8XC9jdy9sxGAO3x830 6Fzg== X-Gm-Message-State: AOJu0YwYgnJdUtdDf3HtBvy/CXrtZWOXZHkDdHtc8PRuMpP/PsUVmmdF Dwoo988Y9xFJUJJl9Q+a/3/enKdRvfCrWBulUhuwvH9xS4BZWAxaMTsrWLv/G0kkIK0= X-Gm-Gg: ASbGncumh0UuP+qdhGF0vtQDPJRXEh1RXL5pu8g6+OPukPu9f4kSSnNtrGgCnNA7MY5 RKrsmBDXkSNR8bowj1y1a/NGY4aMzz7gDBwxfeTUZRkEYWJRZOWsdb4G8HH1sRn0z9ht8y2w1X9 yZXFYjJEici8R0sxo8zn0llpUvcRX6DNuFiwGM+WnpaQ9NHLAU14l/Azh0dHExM9+x6SPAzkVzZ LnFepCYTBdSwfrDZsRapfYcxJOeZWd2DFUb3uVvcNLFKSAc1/G2HY3heWLlmvDKQ37NIlYThpPh jKmiv+SfYD+rNBZR6PBem6I63a0bSOwxlvu+iwwtsUDDl5ICk/Fhad4I22R+WyLgPADStGEGCCt SqvOeEbPLtFU4MjsvhqR9yYEUKRYLI0DLuVgWayBmVT7U5g== X-Google-Smtp-Source: AGHT+IEuhQYgzgTFbOZXUjahrTWsABPfUZy194AF4v8KaCUe4OxfBmwdar9IdKHdJilo4IGaTHcK7g== X-Received: by 2002:a05:6000:22c1:b0:3ec:248f:f86a with SMTP id ffacd0b85a97d-3ecdfa37807mr4725910f8f.48.1758189177722; Thu, 18 Sep 2025 02:52:57 -0700 (PDT) Received: from localhost ([196.207.164.177]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3ee1385adebsm1167298f8f.42.2025.09.18.02.52.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Sep 2025 02:52:57 -0700 (PDT) Date: Thu, 18 Sep 2025 12:52:54 +0300 From: Dan Carpenter To: Jan Kara Cc: linux-fsdevel@vger.kernel.org Subject: [bug report] writeback: Avoid contention on wb->list_lock when switching inodes Message-ID: Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hello Jan Kara, Commit 67c312b4e9bf ("writeback: Avoid contention on wb->list_lock when switching inodes") from Sep 12, 2025 (linux-next), leads to the following Smatch static checker warning: fs/fs-writeback.c:730 cleanup_offline_cgwb() error: uninitialized symbol 'new_wb'. fs/fs-writeback.c 709 bool cleanup_offline_cgwb(struct bdi_writeback *wb) 710 { 711 struct cgroup_subsys_state *memcg_css; 712 struct inode_switch_wbs_context *isw; 713 struct bdi_writeback *new_wb; 714 int nr; 715 bool restart = false; 716 717 isw = kzalloc(struct_size(isw, inodes, WB_MAX_INODES_PER_ISW), 718 GFP_KERNEL); 719 if (!isw) 720 return restart; 721 722 atomic_inc(&isw_nr_in_flight); 723 724 for (memcg_css = wb->memcg_css->parent; memcg_css; 725 memcg_css = memcg_css->parent) { The concern here is that do we know for sure that we enter the loop? 726 new_wb = wb_get_create(wb->bdi, memcg_css, GFP_KERNEL); 727 if (new_wb) 728 break; 729 } --> 730 if (unlikely(!new_wb)) ^^^^^^ These are a common source of false positives, but I just wanted to be sure. Thanks! 731 new_wb = &wb->bdi->wb; /* wb_get() is noop for bdi's wb */ 732 733 nr = 0; regards, dan carpenter