Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754645Ab1CJX5c (ORCPT ); Thu, 10 Mar 2011 18:57:32 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:42034 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754581Ab1CJX52 (ORCPT ); Thu, 10 Mar 2011 18:57:28 -0500 Date: Thu, 10 Mar 2011 15:57:22 -0800 From: "Darrick J. Wong" To: Dave Chinner Cc: Chris Mason , Jan Kara , Joel Becker , "Martin K. Petersen" , Jens Axboe , linux-kernel , linux-fsdevel , Mingming Cao , linux-scsi Subject: Re: [RFC] block integrity: Fix write after checksum calculation problem Message-ID: <20110310235722.GA1110@tux1.beaverton.ibm.com> Reply-To: djwong@us.ibm.com 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> <20110308045626.GD1956@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110308045626.GD1956@dastard> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4906 Lines: 131 On Tue, Mar 08, 2011 at 03:56:26PM +1100, Dave Chinner wrote: > On Fri, Mar 04, 2011 at 01:07:24PM -0800, Darrick J. Wong wrote: > > On Mon, Feb 28, 2011 at 07:54:05AM -0500, Chris Mason wrote: > > > Excerpts from Darrick J. Wong's message of 2011-02-24 13:27:32 -0500: > > > > On Thu, Feb 24, 2011 at 12:37:53PM -0500, Chris Mason wrote: > > > > > Excerpts from Jan Kara's message of 2011-02-24 11:47:58 -0500: > > > > > > On Wed 23-02-11 15:35:11, Chris Mason wrote: > > > > > > > Excerpts from Joel Becker's message of 2011-02-23 15:24:47 -0500: > > > > > > > > On Tue, Feb 22, 2011 at 11:45:44AM -0500, Martin K. Petersen wrote: > > > > > > > > > Also, DIX is only the tip of the iceberg. Many other impending > > > > > > > > > technologies feature checksums and require pages to be stable during I/O > > > > > > > > > due to checksumming, encryption and so on. > > > > > > > > > > > > > > > > > > The VM is already trying to do the right thing. We just need the > > > > > > > > > relevant filesystems to catch up. > > > > > > > > > > > > > > > > ocfs2 handles stable metadata for its checksums when feeding > > > > > > > > things to the journal. If we're doing pagecache-based I/O, is the > > > > > > > > pagecache going to help here for data? > > > > > > > > > > > > > > Data is much easier than metadata. All you really need is to wait on > > > > > > > writeback in file_write, wait on writeback in page_mkwrite, and make Hrm... I've been looking for a file_write in ext4; was the aio_write function pointer what you had in mind here? Adding a wait_on_page_writeback to ext4_page_mkwrite eliminated most of the DIF checksum errors in the mmap case. Unfortunately, I still see them, usually within the first few seconds of kicking off the not-first run. I suspect that may be related to the test program truncating the file after each run causing blocks to come and go, so I'll investigate that part of ext4 next. I also noticed that testing the directio+mmap case exhibits the same symptoms. Anyhow, just attaching the latest hack of mine in case anyone wants to have a look. -- fs: Wait for page writeback when rewrite detected --- fs/buffer.c | 2 ++ fs/ext4/inode.c | 6 +++++- mm/filemap.c | 19 +++++++++++++++++-- mm/memory.c | 3 +++ 4 files changed, 27 insertions(+), 3 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 2219a76..f3639f2 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2369,6 +2369,8 @@ block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, else end = PAGE_CACHE_SIZE; + WARN_ON(!PageLocked(page)); + wait_on_page_writeback(page); ret = __block_write_begin(page, 0, end, get_block); if (!ret) ret = block_commit_write(page, 0, end); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 9f7f9e4..ba45b31 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2762,6 +2762,8 @@ static int ext4_writepage(struct page *page, */ goto redirty_page; } + WARN_ON(!PageLocked(page)); + wait_on_page_writeback(page); if (commit_write) /* now mark the buffer_heads as dirty and uptodate */ block_commit_write(page, 0, len); @@ -5865,12 +5867,14 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) if (PageMappedToDisk(page)) goto out_unlock; + lock_page(page); + /* this one seems to handle mmap */ + wait_on_page_writeback(page); if (page->index == size >> PAGE_CACHE_SHIFT) len = size & ~PAGE_CACHE_MASK; else len = PAGE_CACHE_SIZE; - lock_page(page); /* * return if we have all the buffers mapped. This avoid * the need to call write_begin/write_end which does a diff --git a/mm/filemap.c b/mm/filemap.c index 83a45d3..61af700 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2217,8 +2217,9 @@ 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) +static struct page * +__grab_cache_page_write_begin(struct address_space *mapping, pgoff_t index, + unsigned flags) { int status; struct page *page; @@ -2243,6 +2244,20 @@ 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) { + WARN_ON(!PageLocked(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-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/