From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f177.google.com (mail-yw1-f177.google.com [209.85.128.177]) (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 846EA33C192 for ; Wed, 2 Sep 2026 04:05:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788321919; cv=none; b=gQCrFMQIUi5VxcyiPIEN31lbpV9I6excJidNH8qyl8YhhVVMt/04aZG5rvf9ZVfYr1xlVUxifK/t9TgyWMKXNGFXN1wi5jR4ON9t1VtFlaCd00/SkTiPnJz0whqtRJre+pbwcGhtP2JudvCfTdhW2e1lyhBgZ7bUbKh5Vw79h5s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788321919; c=relaxed/simple; bh=GbeRlDFB/Ojrth/vw1XdAvxwKBOubQN4yOMhkl5AS1k=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=Y259QKAbQ6HbI7SOHEw4HdWbZKu5485x+gs97/ECBiax6+fhJnGZdzXYpb7+nLX+Ch0kC6Alj8QC/76b4/k+Srn+QOtCNmpvqsAMuANF+FLJOLc9Ad0EPzZF0fUa98cu0kjCOP4w98sOQiFuUO99XB/3GZk/+oxzj1I343WvMBg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=SjwjlyGb; arc=none smtp.client-ip=209.85.128.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SjwjlyGb" Received: by mail-yw1-f177.google.com with SMTP id 00721157ae682-855a66e5b5dso7824237b3.0 for ; Tue, 01 Sep 2026 21:05:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788321917; x=1788926717; darn=vger.kernel.org; h=content-type:mime-version:references:message-id:in-reply-to:subject :cc:to:from:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=sggsj0swIY6SNlhR5Rlr4w6l9mVN7Mj25L4G93WgJu0=; b=SjwjlyGbhriZMEkj9jJpqzEk0TtZ2Xzv5+szURgcf7xHhyICpP3fYbcc16LChvSamn L58WyX5AdvRUvEX6zCgYOadE/EPj2UXEmH+0CvdAnm6409JGsekNlgoGUzknnx/pCC48 P8oF/M4vsc5F7eQptLAJ1h7fNDyG3zCz569XLRrUO1AJx+LnZsdAqx86aPCTSBCgsFHw aasUMt30uxz0u8ciA/dCii0d32b+k8l8odbEj7fB7rUkTOoTbAGbItxbtGV0PjHN2vvQ 63Pg/jo9V3kkeQ+KJkpaTGiIJLr7L5eT44UxrVPw+iV+pF4odqGcwYKrdrVUdATl5dxP h2lw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788321917; x=1788926717; h=content-type:mime-version:references:message-id:in-reply-to:subject :cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=sggsj0swIY6SNlhR5Rlr4w6l9mVN7Mj25L4G93WgJu0=; b=LLxvD6Bfoa/iXJgjDFlZy0o669cy9cTR+M57KF9EKFP71Wq28CAy2W1EuqIU2UgBaX 5jFigfSnmYBeoofT0Dcfo4rswJboJ/6cqLjPNtZCJcD4riyXwnHDk/XInhEb5d2cPRwp 8bkIp+yCpJ3NX9e36kgY291/60TCc+Wm+Cqm4pWTCBuBzZsCoYpwc/lcsaT+LeB31Ude JbNJR1fDm8qzQpyx2dUMiZ2eCNddzciQw/tlZ0KbkFLn55qQGvQZXYdk4QTvxKcSnRVK WB5nHiaaBuHUR+oZhyKfVsXiKncKRZnVhh6+DH3VacA8qOW2oxvsOJa2NGoAMETBUgR4 TTHQ== X-Forwarded-Encrypted: i=1; AKwUvBwoBTyVZr3qglZZxTi/4iLx0ANq7QZxgnkcGE/1ZgdYSId+aM4iJ3QDt1pkO3GLCISSLGN98LZs8Mbdk1U=@vger.kernel.org X-Gm-Message-State: AFuF++mZwFdkl0euducM4PmJzdb28N3ZrCCkKEfY23YJbHB+mSG2N4gh YGwLxePNzsuri8Al3uKp6upRbjccimxvcbYBNlJIJrr+UGch/+0ec8ftStOrTzTUhQ== X-Gm-Gg: AYBFou0wsSBcc1I7lkvvDTynD5klkmq5QILXN8GjsZLe2pZFr3kdaf0WN0CelJaDzlm SYzIdMNNLxWQWgA98URjINOH+3aEU/NiRjLaB9CPWBs04XnPsjfDzpHpsR0ZeaL56Nd0optlA5X Pt/GhTXk2kAj6e07r+Z9qt+545m1LPCMEcBK+fEs5ntXZoXAj2QquK25m0TuhWBs8ZWHv8YqdgA MFDTY9ofOUn0sP1wxL235UxLXPx0XY0w8cz1w5biiU/UfMriII/cplO9eE6Q8DW5kVpuoalvezu elf5kOEAfnbbK8SWN4tguwAqp8Azyb1YjHUXPGlCDIkA0nRFavwYPi1+523w/RG9a/zfAgu94K2 bO+rft41ap87x0wPZxVzzzKq0qvTnoIDobLz6WGZ9N55e5fsolfjiQ60gDfpwx9DuBA+gJYdC+m b6QOD6UJeIaopgT718U9bD2iLUvIm4SWDA0uPfzVdbQzusSiktUGhQ4VZPvgoCXmkUbsg+BsATa LInEuvxc57TKYlGZnsNEjB+vaIEfvW8cGm+GQfisiuQ/GxI X-Received: by 2002:a05:690c:81:b0:80b:9f4e:a70 with SMTP id 00721157ae682-86c526f66dfmr8698707b3.26.1788321915018; Tue, 01 Sep 2026 21:05:15 -0700 (PDT) Received: from darker.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id 00721157ae682-86c1975dd91sm8720547b3.49.2026.09.01.21.05.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 21:05:14 -0700 (PDT) Date: Tue, 1 Sep 2026 21:05:09 -0700 (PDT) From: Hugh Dickins To: Andrew Morton cc: Ackerley Tng , Alexander Viro , Baolin Wang , Barry Song , Binbin Wu , Christian Brauner , Christoph Hellwig , Christoph Lameter , Claudio Imbrenda , David Hildenbrand , JP Kobryn , Jan Kara , Jens Axboe , Johannes Weiner , Kairui Song , Kiryl Shutsemau , Lance Yang , Leonardo Bras , Lorenzo Stoakes , Marcelo Tosatti , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michal Hocko , Minchan Kim , Muchun Song , Oscar Salvador , Peter Zijlstra , Qi Zheng , Rik van Riel , Sebastian Andrzej Siewior , Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka , Yang Shi , Yu Zhao , Zach O'Keefe , Zi Yan , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 04/25] mm/fbatch: lru bit set, no extra ref, while folio on per-cpu fbatch In-Reply-To: Message-ID: <04101fb5-a723-1fe0-37ee-5e62b5fbb9d7@google.com> References: <14a16945-529b-8bc0-ab38-3ea97e54e223@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Mon, 24 Aug 2026, Hugh Dickins wrote: ... > --- a/include/linux/mm_inline.h > +++ b/include/linux/mm_inline.h > @@ -343,6 +343,23 @@ static inline void folio_migrate_refs(struct folio *new, const struct folio *old > } > #endif /* CONFIG_LRU_GEN */ > > +enum { > + LRU_NEXT_NEVER_TAIL = 0, /* Used by a tail's compound_head */ > + LRU_NEXT_BATCHED = 1, /* Not used by any aligned pointer */ > + NR_LRU_NEXT_FLAGS > +}; > + > +static __always_inline > +bool lru_add_del_folio(struct folio *folio) > +{ > + /* BUG_ON(folio_test_lru(folio)); */ That was a good statement of intent, but clearly I never booted a system with that BUG_ON uncommented: it actually needs to say /* BUG_ON(folio_test_lru(folio) && folio_ref_count(folio)); */ because once the refcount is 0, __page_cache_release() chooses to lruvec_del_folio() before non-atomically clearing lru flags. To be fixed when respun. > + if (!(folio->lru_next & BIT(LRU_NEXT_BATCHED))) > + return false; > + folio->lru.next = LIST_POISON1; > + /* BUG_ON(folio->lru_next & BIT(LRU_NEXT_BATCHED)); */ > + return true; > +} ...