From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH RFC] introduce ioctl to completely invalidate page cache Date: Fri, 03 Oct 2014 08:28:24 -0600 Message-ID: <542EB288.5000209@kernel.dk> References: <1412266184-23776-1-git-send-email-thanos.makatos@citrix.com> <542DAEAC.8010203@kernel.dk> <2368A3FCF9F7214298E53C823B0A48EC0423DFE3@AMSPEX01CL02.citrite.net> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" , "jlayton@poochiereds.net" , "bfields@fieldses.org" , "jack@suse.cz" To: Thanos Makatos , "linux-fsdevel@vger.kernel.org" Return-path: Received: from mail-pa0-f47.google.com ([209.85.220.47]:58851 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753376AbaJCO22 (ORCPT ); Fri, 3 Oct 2014 10:28:28 -0400 Received: by mail-pa0-f47.google.com with SMTP id rd3so1611406pab.20 for ; Fri, 03 Oct 2014 07:28:28 -0700 (PDT) In-Reply-To: <2368A3FCF9F7214298E53C823B0A48EC0423DFE3@AMSPEX01CL02.citrite.net> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 2014-10-03 03:25, Thanos Makatos wrote: >>> - fsync_bdev(bdev); >>> - invalidate_bdev(bdev); >>> + flush_buffer_cache(bdev); >>> + if (BLKFLSBUF2 == cmd) >>> + return invalidate_inode_pages2( >>> + bdev->bd_inode->i_mapping); >>> return 0; >> >> We're currently ignoring the buffer cache sync and invalidation (which is odd), >> but at least being consistent would be good. >> >> Might also need a filemap_write_and_wait() to sync before invalidation. > > (I've got zero knowledge in this area, so excuse my ignorance!) > > Does filemap_write_and_wait() writes back modified, memory-mapped pages? If so, > isn't there a race condition? Or have I got it completely wrong? There's no race to be concerned of for this ioctl. Any page dirtied before you make the call will be synced, any page dirtied after may not. This is no different than what would happen on the buffer cache side in the current ioctl. -- Jens Axboe