Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932669Ab1CDWWz (ORCPT ); Fri, 4 Mar 2011 17:22:55 -0500 Received: from idcmail-mo2no.shaw.ca ([64.59.134.9]:34153 "EHLO idcmail-mo2no.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932278Ab1CDWWy convert rfc822-to-8bit (ORCPT ); Fri, 4 Mar 2011 17:22:54 -0500 X-Cloudmark-SP-Filtered: true X-Cloudmark-SP-Result: v=1.1 cv=dyVpuHYQJROgCHwBBw1H+I+7e1rgZIKdHwrI0HSbuo4= c=1 sm=1 a=WKMNdXk8PrIA:10 a=BLceEmwcHowA:10 a=kj9zAlcOel0A:10 a=c23vf5CSMVc0QQz9B4a6RA==:17 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=evzLwH17iOcCeDFJ8nUA:9 a=gtjsmCH9Vjgmw397naMA:7 a=FGaQGwpRsN35CIcH8KLmnSQZ1W0A:4 a=CjuIK1q_8ugA:10 a=x8gzFH9gYPwA:10 a=e6qwrDixvCFvde8a:21 a=Vx_Oe6OF1rowUdLz:21 a=HpAAvcLHHh0Zw7uRqdWCyQ==:117 Subject: Re: [RFC] block integrity: Fix write after checksum calculation problem Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=us-ascii From: Andreas Dilger In-Reply-To: <20110304210724.GF27190@tux1.beaverton.ibm.com> Date: Fri, 4 Mar 2011 15:22:30 -0700 Cc: Chris Mason , Jan Kara , Joel Becker , "Martin K. Petersen" , Jens Axboe , linux-kernel , linux-fsdevel , Mingming Cao , linux-scsi Content-Transfer-Encoding: 8BIT Message-Id: <8C2F258E-60BE-45F8-B6E2-87988DEE2776@dilger.ca> References: <20110222020022.GH32261@tux1.beaverton.ibm.com> <20110223202446.GG4020@noexit> <1298493173-sup-8301@think> <20110224164758.GH23042@quack.suse.cz> <1298566775-sup-730@think> <20110224182732.GV27190@tux1.beaverton.ibm.com> <1298897186-sup-9394@think> <20110304210724.GF27190@tux1.beaverton.ibm.com> To: djwong@us.ibm.com X-Mailer: Apple Mail (2.1082) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3932 Lines: 118 On 2011-03-04, at 2:07 PM, Darrick J. Wong wrote: > Ok, here's what I have so far. I took everyone's suggestions of where to add > calls to wait_on_page_writeback, which seems to handle the multiple-write case > adequately. Unfortunately, it is still possible to generate checksum errors by > scribbling furiously on a mmap'd region, even after adding the writeback wait > in the ext4 writepage function. Oddly, I couldn't break btrfs with mmap by > removing its wait_for_page_writeback call, so I suspect there's a bit more > going on in btrfs than I've been able to figure out. Did you add this to ext4_page_mkwrite() or only ext4_writepage()? It wasn't clear from your description above. > The set_memory_ro debugging trick didn't ferret out any write paths that I > didn't catch... though it did have the effect of causing occasional fsync() > deadlocks. I suppose I could sprinkle in a few more of those write calls to > see what happens. > > Either way, I'm emailing to ask everyone's advice since I've run out of ideas. > Or: Did I miss something? > > Thanks all for the feedback so far! > > -- > fs: Wait for page writeback when rewrite detected > > Signed-off-by: Darrick J. Wong > --- > > fs/buffer.c | 4 +++- > fs/ext4/inode.c | 3 +++ > mm/filemap.c | 15 +++++++++++++-- > 3 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 2219a76..39e934c 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -2379,8 +2379,10 @@ block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, > ret = VM_FAULT_OOM; > else /* -ENOSPC, -EIO, etc */ > ret = VM_FAULT_SIGBUS; > - } else > + } else { > + wait_on_page_writeback(page); > ret = VM_FAULT_LOCKED; > + } > > out: > return ret; > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 9f7f9e4..2364704 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -2730,12 +2730,15 @@ static int ext4_writepage(struct page *page, > struct inode *inode = page->mapping->host; > > trace_ext4_writepage(inode, page); > +lock_page(page); > size = i_size_read(inode); > if (page->index == size >> PAGE_CACHE_SHIFT) > len = size & ~PAGE_CACHE_MASK; > else > len = PAGE_CACHE_SIZE; > > +wait_on_page_writeback(page); > + > /* > * If the page does not have buffers (for whatever reason), > * try to create them using __block_write_begin. If this > diff --git a/mm/filemap.c b/mm/filemap.c > index 83a45d3..f201d80 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2217,8 +2217,8 @@ EXPORT_SYMBOL(generic_file_direct_write); > * Find or create a page at the given pagecache position. Return the locked > * page. This function is specifically for buffered writes. > */ > -struct page *grab_cache_page_write_begin(struct address_space *mapping, > - pgoff_t index, unsigned flags) > +struct page *__grab_cache_page_write_begin(struct address_space *mapping, > + pgoff_t index, unsigned flags) > { > int status; > struct page *page; > @@ -2243,6 +2243,17 @@ repeat: > } > return page; > } > +struct page *grab_cache_page_write_begin(struct address_space *mapping, > + pgoff_t index, unsigned flags) > +{ > + struct page *p; > + > + p = __grab_cache_page_write_begin(mapping, index, flags); > + if (p) > + wait_on_page_writeback(p); > + > + return p; > +} > EXPORT_SYMBOL(grab_cache_page_write_begin); > > static ssize_t generic_perform_write(struct file *file, > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/