From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 101F06B02C3 for ; Wed, 9 Aug 2017 23:06:27 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id y206so1473888wmd.1 for ; Wed, 09 Aug 2017 20:06:27 -0700 (PDT) Received: from mail-wm0-x242.google.com (mail-wm0-x242.google.com. [2a00:1450:400c:c09::242]) by mx.google.com with ESMTPS id o7si4137573edj.234.2017.08.09.20.06.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Aug 2017 20:06:26 -0700 (PDT) Received: by mail-wm0-x242.google.com with SMTP id r77so1461649wmd.2 for ; Wed, 09 Aug 2017 20:06:25 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170810030433.GG31390@bombadil.infradead.org> References: <1502175024-28338-1-git-send-email-minchan@kernel.org> <1502175024-28338-3-git-send-email-minchan@kernel.org> <20170808124959.GB31390@bombadil.infradead.org> <20170808132904.GC31390@bombadil.infradead.org> <20170809015113.GB32338@bbox> <20170809023122.GF31390@bombadil.infradead.org> <20170809024150.GA32471@bbox> <20170810030433.GG31390@bombadil.infradead.org> From: Dan Williams Date: Wed, 9 Aug 2017 20:06:24 -0700 Message-ID: Subject: Re: [PATCH v1 2/6] fs: use on-stack-bio if backing device has BDI_CAP_SYNC capability Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: Minchan Kim , Andrew Morton , Linux Kernel Mailing List , linux-mm , Ross Zwisler , "karam . lee" , seungho1.park@lge.com, Christoph Hellwig , Dave Chinner , Jan Kara , Jens Axboe , Vishal Verma , "linux-nvdimm@lists.01.org" , kernel-team On Wed, Aug 9, 2017 at 8:04 PM, Matthew Wilcox wrote: > On Wed, Aug 09, 2017 at 11:41:50AM +0900, Minchan Kim wrote: >> On Tue, Aug 08, 2017 at 07:31:22PM -0700, Matthew Wilcox wrote: >> > On Wed, Aug 09, 2017 at 10:51:13AM +0900, Minchan Kim wrote: >> > > On Tue, Aug 08, 2017 at 06:29:04AM -0700, Matthew Wilcox wrote: >> > > > On Tue, Aug 08, 2017 at 05:49:59AM -0700, Matthew Wilcox wrote: >> > > > > + struct bio sbio; >> > > > > + struct bio_vec sbvec; >> > > > >> > > > ... this needs to be sbvec[nr_pages], of course. >> > > > >> > > > > - bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), >> > > > > + if (bdi_cap_synchronous_io(inode_to_bdi(inode))) { >> > > > > + bio = &sbio; >> > > > > + bio_init(bio, &sbvec, nr_pages); >> > > > >> > > > ... and this needs to be 'sbvec', not '&sbvec'. >> > > >> > > I don't get it why we need sbvec[nr_pages]. >> > > On-stack-bio works with per-page. >> > > May I miss something? >> > >> > The way I redid it, it will work with an arbitrary number of pages. >> >> IIUC, it would be good things with dynamic bio alloction with passing >> allocated bio back and forth but on-stack bio cannot work like that. >> It should be done in per-page so it is worth? > > I'm not passing the bio back and forth between do_mpage_readpage() and > its callers. The version I sent allows for multiple pages in a single > on-stack bio (when called from mpage_readpages()). I like it, but do you think we should switch to sbvec[] to preclude pathological cases where nr_pages is large? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org