Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753988Ab1B1MzF (ORCPT ); Mon, 28 Feb 2011 07:55:05 -0500 Received: from rcsinet10.oracle.com ([148.87.113.121]:28756 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753930Ab1B1MzD (ORCPT ); Mon, 28 Feb 2011 07:55:03 -0500 Content-Type: text/plain; charset=UTF-8 From: Chris Mason To: "Darrick J. Wong" Cc: 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 In-reply-to: <20110224182732.GV27190@tux1.beaverton.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> Date: Mon, 28 Feb 2011 07:54:05 -0500 Message-Id: <1298897186-sup-9394@think> User-Agent: Sup/git Content-Transfer-Encoding: 8bit X-Source-IP: acsmt353.oracle.com [141.146.40.153] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090201.4D6B9B17.0261:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5101 Lines: 128 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 > > > > sure you don't free blocks back to the allocator that are actively under > > > > IO. > > > > > > > > I expect the hard part to be jbd and metadata in ext34. > > > But JBD already has to do data copy if a buffer is going to be modified > > > before/while it is written to the journal. So we should alredy do all that > > > is needed for metadata. I don't say there aren't any bugs as they could be > > > triggered only by crashing at the wrong moment and observing fs corruption. > > > But most of the work should be there... > > > > Most of it is there, but there are always little bits and pieces. The > > ext4 journal csumming code was one semi-recent example where we found > > metadata changing in flight. > > > > A big part of testing this is getting some way to detect the bugs > > without dif/dix. With btrfs I have patches to do set_memory_ro on > > pages once I've don the crc, hopefully we can generalize that idea or > > some up with something smarter. > > Right now I'm faking it with modprobe scsi_debug ato=1 guard=1 dif=3 dix=199. > > Hm, would you mind sharing those patches? I've been working on a second patch > to do the wait-on-writeback per everyone's suggestions, but I still see the > occasional corruption error as soon as I enable the mmap write case and covet > some more debugging tools. It does seem to be working for the pure pwrite() > case. :) Here's an ext4 version of the debugging patch. It's a few years old but it'll give you the idea. This only covers metadata pages. Looks like I hacked the btrfs version up and didn't keep the original, I'll have to rework it, I was trying to use it for the big corruption I fixed recently and made a bunch of changes. For data if mmap is giving you trouble you need to wait on writeback in page_mkwrite, with the page locked. fs/btrfs/inode.c has our page_mkwrite, which uses wait_on_page_writeback() and also the btrfs ordered write code. But for the other filesystems, waiting on writeback should be enough. -chris diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index d4cfd6d..9f278db 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -28,6 +28,16 @@ #include #include +int set_memory_ro(unsigned long addr, int numpages); + +static int set_page_ro(struct page *page) +{ + unsigned long addr = (unsigned long)page_address(page); + if (PageHighMem(page)) + return 0; + return set_memory_ro(addr, 1); +} + /* * Default IO end handler for temporary BJ_IO buffer_heads. */ @@ -639,6 +654,8 @@ void jbd2_journal_commit_transaction(journal_t *journal) set_bit(BH_JWrite, &jh2bh(new_jh)->b_state); wbuf[bufs++] = jh2bh(new_jh); + set_page_ro(jh2bh(new_jh)->b_page); + /* Record the new block's tag in the current descriptor buffer */ diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index a051270..153888e 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -28,6 +28,15 @@ #include static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh); +int set_memory_rw(unsigned long addr, int numpages); +static int set_page_rw(struct page *page) +{ + unsigned long addr = (unsigned long)page_address(page); + if (PageHighMem(page)) + return 0; + return set_memory_rw(addr, 1); +} + /* * jbd2_get_transaction: obtain a new transaction_t object. @@ -1474,9 +1487,11 @@ void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh) break; case BJ_IO: list = &transaction->t_iobuf_list; + set_page_rw(bh->b_page); break; case BJ_Shadow: list = &transaction->t_shadow_list; + set_page_rw(bh->b_page); break; case BJ_LogCtl: list = &transaction->t_log_list; -- 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/