From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C163A2E7631; Tue, 12 May 2026 16:14:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778602455; cv=none; b=GsWS4tlcfOTd6WmEf+SCRHYRo+MERQd706y4XZ8wFBJRdyKRmF1V9mXhyxpRvZg+Nv4y67IqB6v7EhEd1rvxaWgiV49KOv2QxoHvt2ZfQlmHzTaKOptd1UkDy5oovmKDYI00EWUJEH9bGBUMEtGu4NvzDQVwkv9F8G9i+kcQGSk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778602455; c=relaxed/simple; bh=IUNQoj40BBpUNJf0ajtJqYtGemiYL8A1ke06SM7+b4E=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TT4CwthdPK2f4KCeKhXs0d6UfLQNQIAzw7+mmlHz7yfT7nJsW7j8pc/7NPj5HCR7n/19i2OP3Ct95L63un+mYIkctWOUtmumsus8+lKsdmVJpZJQeq3SjHjhj8A+CgQp0dhXgsZpGjg+ZFqRvVYOrEYxRW6KxlSBElYMajILoQ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J/S/PcOS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J/S/PcOS" 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> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512053625.2950900-2-hch@lst.de> 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 > >