From mboxrd@z Thu Jan 1 00:00:00 1970 From: Suzuki Subject: Re: Problem with multiple mounts Date: Wed, 08 Nov 2006 14:38:58 -0800 Message-ID: <45525C82.5080303@linux.vnet.ibm.com> References: <45522E67.7050907@linux.vnet.ibm.com> <20061108203323.GA8238@csclub.uwaterloo.ca> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20061108203323.GA8238@csclub.uwaterloo.ca> Sender: linux-kernel-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Lennart Sorensen Cc: reiserfs-list@namesys.com, lkml , Jan Kara Lennart Sorensen wrote: > On Wed, Nov 08, 2006 at 11:22:15AM -0800, Suzuki wrote: > >>"I exported a disk partition using nbd protocol. On the nbd client, I >>make reiserfs and run fsstress test case on this partition. At the same >>time, I mount this partition on the nbd server. Then Oops appears as >>following:" >> >>ReiserFS: sda10: found reiserfs format "3.6" with standard journal >>ReiserFS: sda10: using ordered data mode >>ReiserFS: sda10: journal params: device sda10, size 8192, journal first >>block 18, max trans len 1024, max batch 900, max commit age 30, max >>trans age 30 >>ReiserFS: sda10: checking transaction log (sda10) >> >>Oops: Kernel access of bad area, sig: 11 [#1] >> >>Call Trace: >>[C000000011333090] [C0000000001EDB70] .journal_read+0x165c/0x1b6c >>(unreliable) >>[C000000011333410] [C0000000001EF280] .journal_init+0xdc0/0xee8 >>[C000000011333530] [C0000000001CDBD8] .reiserfs_fill_super+0xa90/0x1e40 >>[C000000011333790] [C00000000011E988] .get_sb_bdev+0x208/0x31c >>[C000000011333870] [C0000000001CA00C] .get_super_block+0x38/0x60 >>[C000000011333900] [C00000000011E260] .vfs_kern_mount+0xec/0x198 >>[C0000000113339B0] [C00000000011E3E0] .do_kern_mount+0x88/0xdc >>[C000000011333A50] [C0000000001532CC] .do_mount+0xd50/0xe08 >>[C000000011333D60] [C000000000175090] .compat_sys_mount+0x368/0x448 >>[C000000011333E30] [C00000000000861C] syscall_exit+0x0/0x40 >> >>But, if we try the steps in the reverse order, >> >>"mount the partition on nbd server first and then try fsstress tests on >>the client side. This is just to ensure that the server is not seeing an >>incomplete journal created by the client side runs." >> >>Things work fine ! >> >>I doubt if this is due to the mount finding an incomplete journal >>created by the client side fsstress runs in the first scenario. >> >>My question is : Is this supported ? Mounting a filesystem which is >>already mounted and replaying the ( - a may be incomplete- ) journal. > > > Absolutely not supported. Unless you have a filesystem that is > specifically designed for simultanious read-write mount from multiple > places, then you can't. For performance reasons most systems cache > writes and updates in many cases, so the data read by one system may be > out of date because another system has an update waiting to go to disk. > You need a filesystem that has the ability for multiple systems to talk > to each other about updates and locking and such things. Look for a > cluster supporting filesystem or whatever is used to refer to a > filesystem that supports multiple hosts having it mounted to provide > redundant access. No normal filesystem can do it unless everyone has it > mounted read only. If you want to share it, use NFS. That's what it's > for. Thanks for the response. This problem was reported by one of our test team on 2.6.19. So, I wanted to confirm that what they are doing is not supported ! Thanks, Suzuki > > -- > Len Sorensen