From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (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 99CDC3290B8 for ; Thu, 14 May 2026 02:06:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778724380; cv=none; b=CUKhBFdSoYMN8cTXSZ14QHiXiiZBjTfXy141LYCP+ti7DDvIYLuoBkFU4S8ygchsyX+yQQ8tll0fOcsfqVo9xMzf7x9xykXCKUDwTPZyB6s1JDLY6p5nxzL/IQ7DgNgc9uqXPR4T8xTuBAoX8/IQoQ65UsLrqx29z/bICG9Gvlk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778724380; c=relaxed/simple; bh=63rPgjK1ysLMmmhXAjsxS6SA+0Cm0X7hProd38sBWRM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cJX3t7RftweifAk9esRb14wNPQ6VTpkQSyQ7Lu8wuDv8/rHSq93XAC13VsrwHy6zVaimZYNI+8J4tJSvSeNIepLZbGV1FG166JlvOpAU/srK0snQp5MtoEcqvry97x0Rh9ZGmlPuMSVToUiUTeLbh+RKWEDEWsCP+r38E61yrok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=gC0BC+hj; arc=none smtp.client-ip=95.215.58.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="gC0BC+hj" Date: Thu, 14 May 2026 10:06:10 +0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1778724376; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IAyMtvqeP/vr9LGu+3DeKX1bvcCtny0C/Y5rEZXOKs8=; b=gC0BC+hjX+W2nWO5j0p3sh3YySs6ujuigMwTTi0auOpaMD5Hssh1IuEoRhxsm8Bu24/ISO QwDg/O3O3knZwhf26GJuq47rQP6ES/C/B+DIk8bI3JZrq3/VgVkZj+xxU5dtqOiq7yIbAA //wMCyTTBXYFRhrHbjWLz32oM54xkYA= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Baoquan He To: Kairui Song Cc: linux-mm@kvack.org, akpm@linux-foundation.org, chrisl@kernel.org, usama.arif@linux.dev, baohua@kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, youngjun.park@lge.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 2/3] mm/swap: use swap_ops to register swap device's methods Message-ID: References: <20260512104201.716213-1-baoquan.he@linux.dev> <20260512104201.716213-3-baoquan.he@linux.dev> 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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT On 05/13/26 at 01:53am, Kairui Song wrote: > On Tue, May 12, 2026 at 6:50 PM Baoquan He wrote: > > > > This simplifies codes and makes logic clearer. And also makes later any > > new swap device type being added easier to handle. > > > > Currently there are three types of swap devices: bdev_fs, bdev_sync > > and bdev_async, and only operations read_folio and write_folio are > > included. In the future, there could be more swap device types added > > and more appropriate opeations adapted into swap_ops. > > opeations -> operations Will fix, thanks. > > > > > Suggested-by: Chris Li > > Acked-by: Chris Li > > Co-developed-by: Barry Song > > Signed-off-by: Barry Song > > Signed-off-by: Baoquan He > > A few nitpicks below: > > > -void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug) > > -{ > > - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); > > - > > - VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio); > > This sanify check is dropped and not added back in anywhere. This is > fine, but it might be better to have a similar VM_WARN_ON_FOLIO in > swap_writeout? Good catch. In the old code, it's called by both swap_writeout() and zswap_writeback_entry(). In zswap_writeback_entry(), the folio is allocated in-place, we don't need to worry about it now. I am fine to add it back in swap_writeout() because adding it inside all three swap_write_xxx() is a little too much. Cscope tag: __swap_writepage # line filename / context / line 1 288 /home/bhe/code/linux/mm/page_io.c <> __swap_writepage(folio, swap_plug); 2 1053 /home/bhe/code/linux/mm/zswap.c <> __swap_writepage(folio, NULL); > > > void swap_read_folio(struct folio *folio, struct swap_iocb **plug) > > { > > struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); > > @@ -642,13 +664,7 @@ void swap_read_folio(struct folio *folio, struct swap_iocb **plug) > > /* We have to read from slower devices. Increase zswap protection. */ > > zswap_folio_swapin(folio); > > > > - if (data_race(sis->flags & SWP_FS_OPS)) { > > - swap_read_folio_fs(folio, plug); > > - } else if (synchronous) { > > - swap_read_folio_bdev_sync(folio, sis); > > - } else { > > - swap_read_folio_bdev_async(folio, sis); > > - } > > + sis->ops->read_folio(sis, folio, plug); > > > > finish: > > if (workingset) { > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 4840fd40f36f..8c42632e6765 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -3780,6 +3780,15 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > > goto free_swap_zswap; > > } > > > > + /* > > + * init_swap_ops() sets si->ops based on flags. It does not need > > + * swapon_mutex, and must complete before enable_swap_info() > > + * exposes the device. > > + */ > > + error = init_swap_ops(si); > > + if (error) > > + goto bad_swap_unlock_inode; > > I checked the comment above previously and it looked good. But the > error label seems not that correct after double check. inode->i_flags > will keep the S_SWAPFILE flag. Maybe something like add a > inode->i_flags &= ~S_SWAPFILE here and goto free_swap_zswap. Sorry I > didn't check this part carefully last time. Right. How about moving it zswap_swapon() because it only relies on si->flags setting currently? > > But fortunately, init_swap_ops will never fail at this moment so the > issue never triggers. > > > + > > mutex_lock(&swapon_mutex); > > prio = DEF_SWAP_PRIO; > > if (swap_flags & SWAP_FLAG_PREFER) > > diff --git a/mm/zswap.c b/mm/zswap.c > > index 4b5149173b0e..192401f46de4 100644 > > --- a/mm/zswap.c > > +++ b/mm/zswap.c > > @@ -1054,7 +1054,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry, > > folio_set_reclaim(folio); > > > > /* start writeback */ > > - __swap_writepage(folio, NULL); > > + si->ops->write_folio(si, folio, NULL); > > > > out: > > if (ret && ret != -EEXIST) { > > -- > > 2.52.0 > > > > Rest looks good to me! >