From: Andrew Morton Subject: Re: [PATCH] jbd jbd2: fix diowritereturningEIOwhentry_to_release_page fails Date: Tue, 19 Aug 2008 00:16:51 -0700 Message-ID: <20080819001651.30c7620f.akpm@linux-foundation.org> References: <1217971027.7516.20.camel@mingming-laptop> <1218029114.15342.58.camel@think.oraclecorp.com> <20080806135337.GA3615@duck.suse.cz> <1218063477.6383.41.camel@mingming-laptop> <6.0.0.20.2.20080807115853.03f95b78@172.19.0.2> <1218104494.15342.171.camel@think.oraclecorp.com> <6.0.0.20.2.20080808113605.04141328@172.19.0.2> <1218200055.15342.230.camel@think.oraclecorp.com> <6.0.0.20.2.20080811123405.03ec03d0@172.19.0.2> <1218547706.15342.305.camel@think.oraclecorp.com> <20080813101650.GA14392@duck.suse.cz> <1218632396.15342.340.camel@think.oraclecorp.com> <6.0.0.20.2.20080819113242.03f9e8c8@172.19.0.2> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Chris Mason , Jan Kara , Mingming Cao , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, Zach Brown To: Hisashi Hifumi Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:33055 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752044AbYHSHSA (ORCPT ); Tue, 19 Aug 2008 03:18:00 -0400 In-Reply-To: <6.0.0.20.2.20080819113242.03f9e8c8@172.19.0.2> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, 19 Aug 2008 16:03:45 +0900 Hisashi Hifumi wrote: > > At 21:59 08/08/13, Chris Mason wrote: > >On Wed, 2008-08-13 at 12:16 +0200, Jan Kara wrote: > > > >> > With that said, I don't have strong feelings against falling back to > >> > buffered IO when the invalidate fails. Maybe Zach remembers something I > >> > don't? > >> I don't have a strong opinion either. Falling back to buffered writes is > >> simpler at least for ext3/ext4 because properly synchronizing against > >> writepage() call does not seem to have a nice solution either in > >> do_launder_page() or in releasepage(). OTOH is hides the fact the invalidate > >> is failing and so if we screw up something in future and it fails often, it > >> might be hard to notice / track down the performance penalty. > > > >In general, these races don't happen often, and when they do it is > >because someone is mixing page cache and O_DIRECT io to the same file. > >That is explicitly outside the main use case of O_DIRECT. > > > >So, I'd rather see us slow down O_DIRECT in the mixed use case than have > >big impacts in complexity or speed to other parts of the kernel. If > >falling back avoids problems in some filesystems or avoids clearing the > >uptodate bit unexpectedly, I'd much rather take the fallback patch. > > > >-chris > > Hi Andrew. > I think we don't have strong feelings against falling back to buffered writes to > fix the direct-io -EIO problem. > > Please review my patch. > umm, what problem does it solve? > > diff -Nrup linux-2.6.27-rc3.org/mm/filemap.c linux-2.6.27-rc3/mm/filemap.c > --- linux-2.6.27-rc3.org/mm/filemap.c 2008-08-13 13:48:47.000000000 +0900 > +++ linux-2.6.27-rc3/mm/filemap.c 2008-08-19 15:45:31.000000000 +0900 > @@ -2129,13 +2129,20 @@ generic_file_direct_write(struct kiocb * > * After a write we want buffered reads to be sure to go to disk to get > * the new data. We invalidate clean cached page from the region we're > * about to write. We do this *before* the write so that we can return > - * -EIO without clobbering -EIOCBQUEUED from ->direct_IO(). > + * without clobbering -EIOCBQUEUED from ->direct_IO(). > */ > if (mapping->nrpages) { > written = invalidate_inode_pages2_range(mapping, > pos >> PAGE_CACHE_SHIFT, end); > - if (written) > + /* > + * If a page can not be invalidated, return 0 to fall back > + * to buffered write. > + */ > + if (written) { > + if (written == -EBUSY) > + return 0; > goto out; > + } > } > > written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); > diff -Nrup linux-2.6.27-rc3.org/mm/truncate.c linux-2.6.27-rc3/mm/truncate.c > --- linux-2.6.27-rc3.org/mm/truncate.c 2008-08-13 13:48:48.000000000 +0900 > +++ linux-2.6.27-rc3/mm/truncate.c 2008-08-19 12:10:46.000000000 +0900 > @@ -380,7 +380,7 @@ static int do_launder_page(struct addres > * Any pages which are found to be mapped into pagetables are unmapped prior to > * invalidation. > * > - * Returns -EIO if any pages could not be invalidated. > + * Returns -EBUSY if any pages could not be invalidated. > */ > int invalidate_inode_pages2_range(struct address_space *mapping, > pgoff_t start, pgoff_t end) > @@ -440,7 +440,7 @@ int invalidate_inode_pages2_range(struct > ret2 = do_launder_page(mapping, page); > if (ret2 == 0) { > if (!invalidate_complete_page2(mapping, page)) > - ret2 = -EIO; > + ret2 = -EBUSY; > } > if (ret2 < 0) > ret = ret2; If I recall correctly, we had a problem with pages which are pinned by an ext3 transaction, and those pages weren't releaseable for direct-io, and this caused some problem? I think falling back to buffered writes is always a safe course, but it'd be nice to have a full description of the change, please.