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[213.95.11.211]) by mx.google.com with ESMTPS id z75si17626453wmc.151.2019.04.26.07.22.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Apr 2019 07:22:44 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id 6210F68BFE; Fri, 26 Apr 2019 16:22:28 +0200 (CEST) Date: Fri, 26 Apr 2019 16:22:28 +0200 From: Christoph Hellwig To: Andreas Gruenbacher Cc: cluster-devel@redhat.com, Christoph Hellwig , Bob Peterson , Jan Kara , Dave Chinner , Ross Lagerwall , Mark Syms , Edwin =?iso-8859-1?B?VPZy9ms=?= , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v5 2/3] iomap: Add a page_prepare callback Message-ID: <20190426142228.GA16499@lst.de> References: <20190426131127.19164-1-agruenba@redhat.com> <20190426131127.19164-2-agruenba@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190426131127.19164-2-agruenba@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 26, 2019 at 03:11:26PM +0200, Andreas Gruenbacher wrote: > Move the page_done callback into a separate iomap_page_ops structure and > add a page_prepare calback to be called before the next page is written > to. In gfs2, we'll want to start a transaction in page_prepare and end > it in page_done; other filesystems that implement data journaling will > require the same kind of mechanism. > > Signed-off-by: Andreas Gruenbacher > --- > fs/gfs2/bmap.c | 22 +++++++++++++++++----- > fs/iomap.c | 22 ++++++++++++++++++---- > include/linux/iomap.h | 18 +++++++++++++----- > 3 files changed, 48 insertions(+), 14 deletions(-) > > diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c > index 5da4ca9041c0..6b980703bae7 100644 > --- a/fs/gfs2/bmap.c > +++ b/fs/gfs2/bmap.c > @@ -991,15 +991,27 @@ static void gfs2_write_unlock(struct inode *inode) > gfs2_glock_dq_uninit(&ip->i_gh); > } > > -static void gfs2_iomap_journaled_page_done(struct inode *inode, loff_t pos, > - unsigned copied, struct page *page, > - struct iomap *iomap) > +static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos, > + unsigned len, struct iomap *iomap) > +{ > + return 0; > +} > + > +static void gfs2_iomap_page_done(struct inode *inode, loff_t pos, > + unsigned copied, struct page *page, > + struct iomap *iomap) > { > struct gfs2_inode *ip = GFS2_I(inode); > > - gfs2_page_add_databufs(ip, page, offset_in_page(pos), copied); > + if (page) > + gfs2_page_add_databufs(ip, page, offset_in_page(pos), copied); > } > > +static const struct iomap_page_ops gfs2_iomap_page_ops = { > + .page_prepare = gfs2_iomap_page_prepare, > + .page_done = gfs2_iomap_page_done, > +}; > + > static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos, > loff_t length, unsigned flags, > struct iomap *iomap, > @@ -1077,7 +1089,7 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos, > } > } > if (!gfs2_is_stuffed(ip) && gfs2_is_jdata(ip)) > - iomap->page_done = gfs2_iomap_journaled_page_done; > + iomap->page_ops = &gfs2_iomap_page_ops; > return 0; > > out_trans_end: > diff --git a/fs/iomap.c b/fs/iomap.c > index 3e4652dac9d9..ba2d44b33ed1 100644 > --- a/fs/iomap.c > +++ b/fs/iomap.c > @@ -665,6 +665,7 @@ static int > iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > struct page **pagep, struct iomap *iomap) > { > + const struct iomap_page_ops *page_ops = iomap->page_ops; > pgoff_t index = pos >> PAGE_SHIFT; > struct page *page; > int status = 0; > @@ -674,9 +675,17 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > if (fatal_signal_pending(current)) > return -EINTR; > > + if (page_ops) { > + status = page_ops->page_prepare(inode, pos, len, iomap); > + if (status) > + return status; > + } > + > page = grab_cache_page_write_begin(inode->i_mapping, index, flags); > - if (!page) > - return -ENOMEM; > + if (!page) { > + status = -ENOMEM; > + goto no_page; > + } > > if (iomap->type == IOMAP_INLINE) > iomap_read_inline_data(inode, page, iomap); > @@ -684,12 +693,16 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > status = __block_write_begin_int(page, pos, len, NULL, iomap); > else > status = __iomap_write_begin(inode, pos, len, page, iomap); > + > if (unlikely(status)) { > unlock_page(page); > put_page(page); > page = NULL; > > iomap_write_failed(inode, pos, len); > +no_page: > + if (page_ops) > + page_ops->page_done(inode, pos, 0, NULL, iomap); > } > > *pagep = page; I think we need to clean this area up a bit, this is becoming to confusing. Something like: if (unlikely(status)) goto out_unlock; *pagep = page; return 0; out_unlock: unlock_page(page); put_page(page); iomap_write_failed(inode, pos, len); out_no_page: if (page_ops) page_ops->page_done(inode, pos, 0, NULL, iomap); *pagep = NULL; return status; > + if (page_ops) > + page_ops->page_done(inode, pos, copied, page, iomap); Do we always require both pages ops to be set? Wouldn't it be better to check for the method presence as well? > +/* > + * Called before / after processing a page in the mapping returned in this > + * iomap. At least for now, this is only supported in the buffered write path. > + * When page_prepare returns 0, page_done is called as well > + * (possibly with page == NULL). > + */ Not just for now - I think the concept fundamentally only makes sense for buffered I/O. Maybe we need to express that a little more clearly. Otherwise looks fine to me.