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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C0EB9CCD199 for ; Fri, 17 Oct 2025 15:45:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2943B8E0047; Fri, 17 Oct 2025 11:45:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 26BB78E001F; Fri, 17 Oct 2025 11:45:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1822C8E0047; Fri, 17 Oct 2025 11:45:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 026B98E001F for ; Fri, 17 Oct 2025 11:45:09 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 96749B708A for ; Fri, 17 Oct 2025 15:45:08 +0000 (UTC) X-FDA: 84008029896.19.8821FFD Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf03.hostedemail.com (Postfix) with ESMTP id 0308520004 for ; Fri, 17 Oct 2025 15:45:06 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Kym3Qj/1"; spf=pass (imf03.hostedemail.com: domain of djwong@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1760715907; a=rsa-sha256; cv=none; b=BGGhkHNpJ0CdwLairIEfAitVBmdVOLz/mRd451pj8lJPjGiDggDiHWTdQyUBK5TDTpqUWr bd5leMGF8Op3lpO9gy8zk1v86LuoZmY/qVi+aBOhWsLpPczK7i1YAGiZVnR92dZP5h9C6m ox33Mw0UqUF9gi+9eznk4samJSwxp7A= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Kym3Qj/1"; spf=pass (imf03.hostedemail.com: domain of djwong@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760715907; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=T1c1dv8QjcSijwB4PTfLy/R64Ra9NB8M/WbGg411sG0=; b=JSdVNjgpuWFWONi+xWTpEI6lSuK95v6Zo1kwZ0fyDC8OkOV0qLBwJqABd1GHrzWTsemzkU oWAY80He/0mh5A4YPbktyRs0JUbETGmbl812ATZdjDgsIOVyg8MfbfBD5jVGpb28ZCIGwy l2KuM5/0RR4nkOsbCQxeu3pGS7Vx1c4= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 7218F6465D; Fri, 17 Oct 2025 15:45:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 17664C4CEE7; Fri, 17 Oct 2025 15:45:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760715906; bh=hsyaCroZlOpyDIPtwc0w/ZFBWjk/QkbVl30D1Hma/F8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Kym3Qj/1oqjNnBDMDOACUt16lqnELIDADwAxk+3t/U1kOC8GbtA+5DL8fdqFb8mCV 3OTmnKNuU/eMWWUmPt5dJXe/TpD7eBOyMFKFxMJGqSP4+ztRVP7EPp9ptY9vYagCmY qco02GBiZXkDgYVL/iMcgrlh3o+vsM6T+RcnUAi+gzkPZxidI/a3/5fDhWVcJje5YL m+XEa9bLIjdI1tNIwcFarMeMtqY6b0wUnu0UuSCnY3UY4me6QKUvLFZ+xu77BJtHBw 4eGZTLs/5p+ErJLOaf0q+x/3hoa1TyhfGPFKbsRy0MIMLBGTXW2LcLPJzru4NmuZY8 Q7g532pVrbEmQ== Date: Fri, 17 Oct 2025 08:45:05 -0700 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Christian Brauner , Jan Kara , Carlos Maiolino , Andrew Morton , willy@infradead.org, dlemoal@kernel.org, hans.holmberg@wdc.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org Subject: Re: [PATCH 2/3] writeback: allow the file system to override MIN_WRITEBACK_PAGES Message-ID: <20251017154505.GE6174@frogsfrogsfrogs> References: <20251017034611.651385-1-hch@lst.de> <20251017034611.651385-3-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251017034611.651385-3-hch@lst.de> X-Rspam-User: X-Stat-Signature: sxkuxx36hqin88nixa9way5a94a7m35p X-Rspamd-Queue-Id: 0308520004 X-Rspamd-Server: rspam09 X-HE-Tag: 1760715906-687036 X-HE-Meta: U2FsdGVkX18ROJJYq2yt25Xa0C63Vt1OyTZZn6Q5t1M6qqZS+A3gNku2dgEmNjavzeB14ODwMQaLwTsciHp+gfH3wczwOGQ3AGRN4fG+celmHqfHqfKFdBZ3ZEuJ/tkK5C9lklfkMhMOQm/08eMm49zRCpU63p5ijmBjqTqhEKciTK+nI5nyOjeHXKurX1IOvUwDCcFzCEjbRwLRmoIjgVJL190KWCl95tUZcwGUdDUiEEAVvpeXO6aUNgGjmMmFeLuElutcUQHLjfepquRMgu5U45BePcXrcGoZUVQIcojAU1fTLYYLnigKuzBMtztxA9OdRP8qDzGRibg0z81lxxbWe1N8Bl0HKJAnOaXZXh9jgM1M43ZNvdcw8rVm2s3W2B4cfGHeohO6/CQdnE1LreOTxrRfDEtXNuLwpjsdW2HY2KSNDpnhygX0R8/tbRHPYSRqsUPSwbILzn6pjSd4uUNiYyUqr+NdQXRtkPqqr5ZznoLRtwJaxGYxCCOZo1EPfdYF6j3wzgt22K8JxVB0gn3o6/jv8BpKaczyg32iAnovIW5QXQUE+rzJgUZ0IOcQ/Ba1e+qfLfQaZYx4N/oo3RFFTko6iTA4WdTiv3IGuRhuPaUFhxKs3EOhIiwIsW0mrGUw98uMdRzX5Vf241IKqKFYmo+Q9M46GEmXL2YjNnV97IXuy9umkoU0Dm5bo4/z2SAjDkBuZaXzSFR3kTPbdZ27F73B4bmEO4ejjdt0zRBrEUH5tUWb4O9mJbqLezOBlxm4ij/6sWBwWUoB9HC7vkrKmNN5LguyN6esW6rlzsAVKydgDd/6gaT0Q3fxdMUhYeTMhpH4f3ZQLb4ifta4zJ6wD9i+ZJ50N5YXaZ+yFZUzjASLTw7LP9GrlTluKZchAGaZr4ERGNFnqHhzGZsePdh2KAX9q9Z6feQ5uhAVi6ey3is6loBVSlfoizpPouxpbd5ByX6juPvshv7AdpK r9PBleri vtavKhUYAbSKfeYAZFniwiWoN4Umbfwimp+3Ca/hvfV8/gtnbd1vELUFl4cqdBYNjhRCTrrMZGSxQHQyhH6Vk29l2xRrrSaLNxRv+E0vcUXYqWFu1TM/Q5y0tYOuNdiF1jmVRD8ApUZWGHuTYVMAiA06T21F1buNIigOM1msxqQqc2/d8mI1mTHAu4vZtUJj+FRmYKuE/elFyrRtyQN+rsWcFvF391tGCoQVEJY1+RoE3l2o/HQmDpF13mlvQWfFLugG73O8kBA4bA8dpneVFjS4U9q03YLbQ+yOzxyLbYps6pq5gQkIVZJrxg31o0AM2RKb3HZzwddorbXN7GKmkUnpchCFMrlIVhiSJ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 17, 2025 at 05:45:48AM +0200, Christoph Hellwig wrote: > The relatively low minimal writeback size of 4MiB means that written back > inodes on rotational media are switched a lot. Besides introducing > additional seeks, this also can lead to extreme file fragmentation on > zoned devices when a lot of files are cached relative to the available > writeback bandwidth. > > Add a superblock field that allows the file system to override the > default size. > > Signed-off-by: Christoph Hellwig The comment in the next patch satisfies me sufficiently, so Reviewed-by: "Darrick J. Wong" --D > --- > fs/fs-writeback.c | 14 +++++--------- > fs/super.c | 1 + > include/linux/fs.h | 1 + > include/linux/writeback.h | 5 +++++ > 4 files changed, 12 insertions(+), 9 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 11fd08a0efb8..6d50b02cdab6 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -31,11 +31,6 @@ > #include > #include "internal.h" > > -/* > - * 4MB minimal write chunk size > - */ > -#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10)) > - > /* > * Passed into wb_writeback(), essentially a subset of writeback_control > */ > @@ -1874,8 +1869,8 @@ static int writeback_single_inode(struct inode *inode, > return ret; > } > > -static long writeback_chunk_size(struct bdi_writeback *wb, > - struct wb_writeback_work *work) > +static long writeback_chunk_size(struct super_block *sb, > + struct bdi_writeback *wb, struct wb_writeback_work *work) > { > long pages; > > @@ -1898,7 +1893,8 @@ static long writeback_chunk_size(struct bdi_writeback *wb, > pages = min(wb->avg_write_bandwidth / 2, > global_wb_domain.dirty_limit / DIRTY_SCOPE); > pages = min(pages, work->nr_pages); > - return round_down(pages + MIN_WRITEBACK_PAGES, MIN_WRITEBACK_PAGES); > + return round_down(pages + sb->s_min_writeback_pages, > + sb->s_min_writeback_pages); > } > > /* > @@ -2000,7 +1996,7 @@ static long writeback_sb_inodes(struct super_block *sb, > inode->i_state |= I_SYNC; > wbc_attach_and_unlock_inode(&wbc, inode); > > - write_chunk = writeback_chunk_size(wb, work); > + write_chunk = writeback_chunk_size(inode->i_sb, wb, work); > wbc.nr_to_write = write_chunk; > wbc.pages_skipped = 0; > > diff --git a/fs/super.c b/fs/super.c > index 5bab94fb7e03..599c1d2641fe 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -389,6 +389,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags, > goto fail; > if (list_lru_init_memcg(&s->s_inode_lru, s->s_shrink)) > goto fail; > + s->s_min_writeback_pages = MIN_WRITEBACK_PAGES; > return s; > > fail: > diff --git a/include/linux/fs.h b/include/linux/fs.h > index c895146c1444..ae6f37c6eaa4 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1583,6 +1583,7 @@ struct super_block { > > spinlock_t s_inode_wblist_lock; > struct list_head s_inodes_wb; /* writeback inodes */ > + long s_min_writeback_pages; > } __randomize_layout; > > static inline struct user_namespace *i_user_ns(const struct inode *inode) > diff --git a/include/linux/writeback.h b/include/linux/writeback.h > index 22dd4adc5667..49e1dd96f43e 100644 > --- a/include/linux/writeback.h > +++ b/include/linux/writeback.h > @@ -374,4 +374,9 @@ bool redirty_page_for_writepage(struct writeback_control *, struct page *); > void sb_mark_inode_writeback(struct inode *inode); > void sb_clear_inode_writeback(struct inode *inode); > > +/* > + * 4MB minimal write chunk size > + */ > +#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10)) > + > #endif /* WRITEBACK_H */ > -- > 2.47.3 > >