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 04A4E357D08; Tue, 12 May 2026 07:08:41 +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=1778569722; cv=none; b=ZacpkcsJD/F3dELlzrPe8rrb0XbUq3+VehYSBxgHLHxyPrLhm8h1DVTFkKx4vTJ8TGUa6nM1zYNwJzXKMkGrFhIEGUkST6kktVBFLtzSdZkJCpfiblZP+JzP5Z6vKBQ9H5GYmuAl2JNs7UU5DzMhdnmiimNZ3/iJ+eK/VuDjRZ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778569722; c=relaxed/simple; bh=5R+EGY533uqCmLzbRat4246szQJrvxiGXh+zrcNZP8Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qZ/tT+5p2sM4JWHzRLZkPhbZC1yih/gvOJK9nyvA5tVfDW6cvm+Jgvfoy7SevddRJlhhJzGd+WDLpw+TPbpvVvg7LIvcRew3rbikdnLLn5s37GpyGC+PB8Ta6Tmi3H4MAhlusbVHNfD8Jj4bXbiubTFZoOdhU6+BBoIf4vizWlg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AZVW7Qui; 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="AZVW7Qui" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0E6A5C2BCFD; Tue, 12 May 2026 07:08:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778569721; bh=5R+EGY533uqCmLzbRat4246szQJrvxiGXh+zrcNZP8Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=AZVW7Qui1CP12PCsES+DAfGefhgG6ZsGG+IPd29OfkaPW+1CkthidE8AZJwY75U0C 4rNrhnRBljNrhbvZDbEiEgSRDdXMcjdraEcCwuiJdxsOXLKnGqhSVmrr/6hhPR2x9L 5vwiYRzb+7Elk2tmObpq81hcArgCm9ZegwZDJEAkv9M9iicfMeRn5NaRYpNZWqfPOE 2HWszZ/4Gxf/5HGNX9W/seayQBqvEPgMe4Hs7m6wvAkzGhJbO9TvFDGMPWP3Yn5FY9 SZ27OhjGJ/CoGsGG5mf9JCFTzQ3uplWm0vr4OAI+NqYEiilCS2Y4tpjuYjp3Qie9BH /RQBnxU6ladzQ== Message-ID: <03dddf72-8755-4ebf-ba79-456377f0f25d@kernel.org> Date: Tue, 12 May 2026 16:08:35 +0900 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/12] swap: remove the maxpages variable in sys_swapon To: Christoph Hellwig , Andrew Morton , Chris Li , Kairui Song Cc: Christian Brauner , "Darrick J . Wong" , 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 , 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 References: <20260512053625.2950900-1-hch@lst.de> <20260512053625.2950900-2-hch@lst.de> Content-Language: en-US From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <20260512053625.2950900-2-hch@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/12/26 14:35, Christoph Hellwig wrote: > Always use si->max which is updated setup_swap_extents instead of copying > into and out of maxpages. Checking mm/swapfile.c, I see s->max being set only in swapon(). Is this a typo or am I misunderstanding this sentence ? Looks good otherwise, but it would be nice to rename ->max to ->maxpages to make it clear what this is counting. > > Signed-off-by: Christoph Hellwig > --- > 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; > -- Damien Le Moal Western Digital Research