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 939DCCD4F24 for ; Tue, 12 May 2026 16:14:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C30996B009B; Tue, 12 May 2026 12:14:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BE1376B009E; Tue, 12 May 2026 12:14:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AA8F26B00A0; Tue, 12 May 2026 12:14:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 9372C6B009B for ; Tue, 12 May 2026 12:14:18 -0400 (EDT) Received: from smtpin12.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 41A0E8D0CD for ; Tue, 12 May 2026 16:14:18 +0000 (UTC) X-FDA: 84759264996.12.0791C67 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf20.hostedemail.com (Postfix) with ESMTP id 7EF311C0003 for ; Tue, 12 May 2026 16:14:16 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="J/S/PcOS"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of djwong@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=djwong@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778602456; 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=jVM4DfUVCcEgrG+8nfDyufkWHXji2ICb2GvkaG2MzZE=; b=D7E9/lwhKw1zHkNm1zkIVmHrrYUjDH+DhM1P94r3esZVmadHk9QdcQvZCs+tzaQqqI4cIq sigrNKpMl3eTMftygS0tafEnHw4BIoZ7CYW8ZHgQTxuFfw2NhWgRXga/t9gV21Vp4VAk1z Wcia/i9tyc5KqzJ3N2u6A7VOz7UaoJY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778602456; a=rsa-sha256; cv=none; b=QS52ygkIAqGIMsE0gUHhHaLj0pVAyKpKx0JLUSk9kWQUOlkDmvr4uViexhDujf/q0VdRgl EAHaRT1FFajAJpH2n3ytTvNAgJniCnTHflv03Syz69UJWTEDstRife5B2Sc/9FlSDfXRn3 9+tVn7i0JQ09pKW4aSsXs4kGS/EV448= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="J/S/PcOS"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of djwong@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=djwong@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 90FC943D00; Tue, 12 May 2026 16:14:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 646AEC2BCFA; Tue, 12 May 2026 16:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778602455; bh=IUNQoj40BBpUNJf0ajtJqYtGemiYL8A1ke06SM7+b4E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=J/S/PcOS1XPcZV7Syc+JlqArxkXZ/hbxBjwDT1oINHHwBvkhhEWP9INmRvwBy5uMs IQ7LRTkDcpdEEKM0Tw08keNfDow4yaHa7b0CVm3jBd1tISNFLljNv2sMqAGoS/qtXU kvv4bupqJjw57mXwLGv3YQYnlWf91aYSUfKamfSgWAYibwIdHaKI2hKtoE8SnMjl/r yss2iKimG4E33ynm2qH/k2CFu5aRhuOAM/21vTLClYeYWVJ5nzDy2SveAFpZ27Z4QK HnDMLSECA8B5Mln82mBvnzgxuWuoXQxgVvLQ2dQycDnG6am4VL4o8Rvgtxso9ns8vD fQ/KjPYMec+yg== Date: Tue, 12 May 2026 09:14:14 -0700 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Andrew Morton , Chris Li , Kairui Song , Christian Brauner , Jens Axboe , David Sterba , Theodore Ts'o , Jaegeuk Kim , Chao Yu , Trond Myklebust , Anna Schumaker , Namjae Jeon , Hyunchul Lee , Steve French , Paulo Alcantara , Carlos Maiolino , Damien Le Moal , Naohiro Aota , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org Subject: Re: [PATCH 01/12] swap: remove the maxpages variable in sys_swapon Message-ID: <20260512161414.GB9555@frogsfrogsfrogs> References: <20260512053625.2950900-1-hch@lst.de> <20260512053625.2950900-2-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512053625.2950900-2-hch@lst.de> X-Rspam-User: X-Rspamd-Queue-Id: 7EF311C0003 X-Rspamd-Server: rspam04 X-Stat-Signature: yrejcdh1gzyziksa9wd477tkmqoup4yb X-HE-Tag: 1778602456-479341 X-HE-Meta: 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 rWlvePwU i24meGgy9wPS8vGC7ZvcRMLktURQ+NVIV/Xw/FO1QIV5cf7m1HsH/AsFbdo6r/FyHakaHfEsDZSD5wBqYKf14/qFYBtbFJCwgAEPnJNtBnLOU7nApBv5ZR8pUFVuI7jgUY6/ZOxurj9uq9wmEMWSE2c0uAWj38IQ6kW/0f+5qf3lUd1PnDd3SsaFTbf/tjgCQCzpc9sMX9lzgm9YUtljiRUUPodyeUVALLEYjW/xHKDFIxOgszqJGZL6AwEwJWUu7zyGKymuMlrYzGFB6Sm+fedEybz2BRjoz2XK8e0sk65/ntZaRm8+WHE02XEbvc3zeY3Gm6HspRRfmx1UC/3vGBjh6PprYUtrcDY+9GicVb/Em1jz90r4jw6SvhyrbADMguMbzW68PE5K/7wDsDH7XceipfFOGOS1luxMafX1lrLCeUDE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, May 12, 2026 at 07:35:17AM +0200, Christoph Hellwig wrote: > Always use si->max which is updated setup_swap_extents instead of copying "...updated in setup_swap_extents..." > into and out of maxpages. > > Signed-off-by: Christoph Hellwig But yes, it's much harder to track the data flows if we keep copying the value in and out of local variables. Reviewed-by: "Darrick J. Wong" --D > --- > mm/swapfile.c | 27 +++++++++++---------------- > 1 file changed, 11 insertions(+), 16 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 9174f1eeffb0..f7ebd97e28a3 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -3350,10 +3350,9 @@ static unsigned long read_swap_header(struct swap_info_struct *si, > } > > static int setup_swap_clusters_info(struct swap_info_struct *si, > - union swap_header *swap_header, > - unsigned long maxpages) > + union swap_header *swap_header) > { > - unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); > + unsigned long nr_clusters = DIV_ROUND_UP(si->max, SWAPFILE_CLUSTER); > struct swap_cluster_info *cluster_info; > int err = -ENOMEM; > unsigned long i; > @@ -3395,7 +3394,7 @@ static int setup_swap_clusters_info(struct swap_info_struct *si, > if (err) > goto err; > } > - for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++) { > + for (i = si->max; i < round_up(si->max, SWAPFILE_CLUSTER); i++) { > err = swap_cluster_setup_bad_slot(si, cluster_info, i, true); > if (err) > goto err; > @@ -3425,7 +3424,7 @@ static int setup_swap_clusters_info(struct swap_info_struct *si, > si->cluster_info = cluster_info; > return 0; > err: > - free_swap_cluster_info(cluster_info, maxpages); > + free_swap_cluster_info(cluster_info, si->max); > return err; > } > > @@ -3440,7 +3439,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > union swap_header *swap_header; > int nr_extents; > sector_t span; > - unsigned long maxpages; > struct folio *folio = NULL; > struct inode *inode = NULL; > bool inced_nr_rotate_swap = false; > @@ -3512,14 +3510,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > } > swap_header = kmap_local_folio(folio, 0); > > - maxpages = read_swap_header(si, swap_header, inode); > - if (unlikely(!maxpages)) { > + si->max = read_swap_header(si, swap_header, inode); > + if (unlikely(!si->max)) { > error = -EINVAL; > goto bad_swap_unlock_inode; > } > > - si->max = maxpages; > - si->pages = maxpages - 1; > + si->pages = si->max - 1; > nr_extents = setup_swap_extents(si, swap_file, &span); > if (nr_extents < 0) { > error = nr_extents; > @@ -3531,14 +3528,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > goto bad_swap_unlock_inode; > } > > - maxpages = si->max; > - > /* Set up the swap cluster info */ > - error = setup_swap_clusters_info(si, swap_header, maxpages); > + error = setup_swap_clusters_info(si, swap_header); > if (error) > goto bad_swap_unlock_inode; > > - error = swap_cgroup_swapon(si->type, maxpages); > + error = swap_cgroup_swapon(si->type, si->max); > if (error) > goto bad_swap_unlock_inode; > > @@ -3546,7 +3541,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > * Use kvmalloc_array instead of bitmap_zalloc as the allocation order might > * be above MAX_PAGE_ORDER incase of a large swap file. > */ > - si->zeromap = kvmalloc_array(BITS_TO_LONGS(maxpages), sizeof(long), > + si->zeromap = kvmalloc_array(BITS_TO_LONGS(si->max), sizeof(long), > GFP_KERNEL | __GFP_ZERO); > if (!si->zeromap) { > error = -ENOMEM; > @@ -3597,7 +3592,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > } > } > > - error = zswap_swapon(si->type, maxpages); > + error = zswap_swapon(si->type, si->max); > if (error) > goto bad_swap_unlock_inode; > > -- > 2.53.0 > >