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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9EF89C433EF for ; Sun, 26 Sep 2021 23:09:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8402A61151 for ; Sun, 26 Sep 2021 23:09:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231979AbhIZXKg (ORCPT ); Sun, 26 Sep 2021 19:10:36 -0400 Received: from esa5.hgst.iphmx.com ([216.71.153.144]:2900 "EHLO esa5.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232048AbhIZXKf (ORCPT ); Sun, 26 Sep 2021 19:10:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=wdc.com; i=@wdc.com; q=dns/txt; s=dkim.wdc.com; t=1632697737; x=1664233737; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=TDOTPmawcYz4rmiMAIYJQQx5dPP35Ldh0mdFUTfrChI=; b=ak++SGTJXJHjtj8QwbHXn3zAZVY+7BYQC63ZMZMQrrRu2FOPWU1JLhwg EwNV/vGwamcgpsvjdFTl5Z0dW4RiM3/M7zPMerpXoX2tBBzwqEZBAxAwH RVuptlDR2Xqak8YtNQQINJIxHKzqwsvQf3Rf7blkIdZTJbENLyc7fXACW nPyNSzXSqcYMcTWtyaMMcC89P4PxBngfAGFhMdkepDxdGsKVOyLT0voXl gM6jnpnShIFKf4elVhMFyegpfnrWuMYEEQ9hTDdLWbrxeIUoT/HLg6I0M J4JlgJbDZKZdGX+Q1uZ5DP4aC3ZvxomWGAjcSAS/KvHUMVLyByjNUEInz g==; X-IronPort-AV: E=Sophos;i="5.85,325,1624291200"; d="scan'208";a="181015787" Received: from uls-op-cesaip01.wdc.com (HELO uls-op-cesaep01.wdc.com) ([199.255.45.14]) by ob1.hgst.iphmx.com with ESMTP; 27 Sep 2021 07:08:57 +0800 IronPort-SDR: ICcqwBDFwh80OGx87GM9RFEoejF60p2+6z4E3r4T6MoEbxMVzD5pgo+C3rHqVLR39uOGxyUNSD ZbL+IHOPPimjw4rTLZsT0t3ylB8k9p+/0FYqVHO84rM73wmjV/bi1EcXe+XlX7mSsRBLbgioMZ pRs+1C9f0ges8vOiWrqmaPhf/oVIeF6bR8WjRafBraZ05DmiUKW628F2ul3D0lmjmel26zB/c6 QZhBKRLlYDiHEJobb2Q5tHeUyguj44Ttori+O+BbXriAhd+myTTzGu18G0XXmJZAfpWojmttFg 8PjJ78icnynBcpuHtk4CeJBx Received: from uls-op-cesaip01.wdc.com ([10.248.3.36]) by uls-op-cesaep01.wdc.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Sep 2021 15:45:05 -0700 IronPort-SDR: jqO9itrV3hJEY/oDIrcoZC4K1L0poyjj5vjzwyeVaehXygmzx9la8mabxfjkfgDpwIOcpE4Tgb 9RCrSO6yDZ9Fy1HiDS5JCtAsK3QJMvqpsPh2MRa577cy5Od9ruPtM/pQ2vyT91YuDpbKYOr9HA fiWyX77jh8yVXBu/os8gfxZ3ePE/yahTJJUz/fy7AV9aEXqHTClgzqKFfc4LD2Y0EcFMUjmosP hLWPTPZpNTmcg/1zUQcfxGUdArTKhFMKR93FXcvnm3S7BIzgsawk0Y7h2CipQBWwGgHXhtfpTx ccY= WDCIronportException: Internal Received: from usg-ed-osssrv.wdc.com ([10.3.10.180]) by uls-op-cesaip01.wdc.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Sep 2021 16:08:58 -0700 Received: from usg-ed-osssrv.wdc.com (usg-ed-osssrv.wdc.com [127.0.0.1]) by usg-ed-osssrv.wdc.com (Postfix) with ESMTP id 4HHhKQ2p2cz1Rvlf for ; Sun, 26 Sep 2021 16:08:58 -0700 (PDT) Authentication-Results: usg-ed-osssrv.wdc.com (amavisd-new); dkim=pass reason="pass (just generated, assumed good)" header.d=opensource.wdc.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d= opensource.wdc.com; h=content-transfer-encoding:content-type :in-reply-to:organization:from:references:to:content-language :subject:user-agent:mime-version:date:message-id; s=dkim; t= 1632697737; x=1635289738; bh=TDOTPmawcYz4rmiMAIYJQQx5dPP35Ldh0md FUTfrChI=; b=TmqmtvnUWB/0fOST0cEzXPQ5EjlnNrPpSxR+bjf6UJqZZo55P3D FIoK8AI8+hr11KKXdI9k4f+fj7jXDyP+GSOexgk0xQ5mvJef7ZgJvnuC6IfeSIxu 68YNCNVQ/KNmrGCLycrn5vhJmh7iefjax+lFC53KM9o6w0POibu9PNHkEiXeA9GO gl732LcWzZi0+Eh76bIZJ07k9YXnl8VYPQcR6VMWAdskcbLH7wUyZXqpzFX9nOqn Q1Syji8+Zfe5lPXeAqSxX7a3Uzh6sEh0tLn4ixpeKfBTVQFKr4wfz9w2ASbpPiGH D7WlSzZ0SuLjRdJmxdhMRyEoDIkt+zeXcPA== X-Virus-Scanned: amavisd-new at usg-ed-osssrv.wdc.com Received: from usg-ed-osssrv.wdc.com ([127.0.0.1]) by usg-ed-osssrv.wdc.com (usg-ed-osssrv.wdc.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id ohNM2JB8nnEK for ; Sun, 26 Sep 2021 16:08:57 -0700 (PDT) Received: from [10.89.85.1] (c02drav6md6t.dhcp.fujisawa.hgst.com [10.89.85.1]) by usg-ed-osssrv.wdc.com (Postfix) with ESMTPSA id 4HHhKL6dDzz1RvTg; Sun, 26 Sep 2021 16:08:54 -0700 (PDT) Message-ID: <5fde9167-6f8b-c698-f34d-d7fafd4219f7@opensource.wdc.com> Date: Mon, 27 Sep 2021 08:08:53 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.1.1 Subject: Re: [PATCH v3 9/9] mm: Remove swap BIO paths and only use DIO paths Content-Language: en-US To: Matthew Wilcox , David Howells Cc: hch@lst.de, trond.myklebust@primarydata.com, Jens Axboe , "Darrick J. Wong" , linux-block@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, darrick.wong@oracle.com, viro@zeniv.linux.org.uk, jlayton@kernel.org, torvalds@linux-foundation.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <163250387273.2330363.13240781819520072222.stgit@warthog.procyon.org.uk> <163250396319.2330363.10564506508011638258.stgit@warthog.procyon.org.uk> <2396106.1632584202@warthog.procyon.org.uk> From: Damien Le Moal Organization: Western Digital In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On 2021/09/26 2:09, Matthew Wilcox wrote: > On Sat, Sep 25, 2021 at 04:36:42PM +0100, David Howells wrote: >> Matthew Wilcox wrote: >> >>> On Fri, Sep 24, 2021 at 06:19:23PM +0100, David Howells wrote: >>>> Delete the BIO-generating swap read/write paths and always use ->swap_rw(). >>>> This puts the mapping layer in the filesystem. >>> >>> Is SWP_FS_OPS now unused after this patch? >> >> Ummm. Interesting question - it's only used in swap_set_page_dirty(): >> >> int swap_set_page_dirty(struct page *page) >> { >> struct swap_info_struct *sis = page_swap_info(page); >> >> if (data_race(sis->flags & SWP_FS_OPS)) { >> struct address_space *mapping = sis->swap_file->f_mapping; >> >> VM_BUG_ON_PAGE(!PageSwapCache(page), page); >> return mapping->a_ops->set_page_dirty(page); >> } else { >> return __set_page_dirty_no_writeback(page); >> } >> } > > I suspect that's no longer necessary. NFS was the only filesystem > using SWP_FS_OPS and ... > > fs/nfs/file.c: .set_page_dirty = __set_page_dirty_nobuffers, > > so it's not like NFS does anything special to reserve memory to write > back swap pages. > >>> Also, do we still need ->swap_activate and ->swap_deactivate? >> >> f2fs does quite a lot of work in its ->swap_activate(), as does btrfs. I'm >> not sure how necessary it is. cifs looks like it intends to use it, but it's >> not fully implemented yet. zonefs and nfs do some checking, including hole >> checking in nfs's case. nfs also does some setting up for the sunrpc >> transport. >> >> btrfs, cifs, f2fs and nfs all supply ->swap_deactivate() to undo the effects >> of the activation. > > Right ... so my question really is, now that we're doing I/O through > aops->direct_IO (or ->swap_rw), do those magic things need to be done? > After all, open(O_DIRECT) doesn't do these same magic things. They're > really there to allow the direct-to-BIO path to work, and you're removing > that here. For zonefs, ->swap_activate() checks that the user is not trying to use a sequential write only file for swap. Swap cannot work on these files as there are no guarantees that the writes will be sequential. -- Damien Le Moal Western Digital Research