[Bugme-new] [Bug 9044] New: Local NFS mounts lead to system lockups

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=9044

           Summary: Local NFS mounts lead to system lockups
           Product: File System
           Version: 2.5
     KernelVersion: 2.6.22
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: NFS
        AssignedTo: trond.myklebust at fys.uio.no
        ReportedBy: muehlenhoff at univention.de


Most recent kernel where this bug did not occur:
Distribution: Tested both on Gentoo and a Debian 4.0-based distribution
Hardware Environment: i386 (two different hardware setups)
Software Environment:
Problem Description:

NFS mounts lead to system lockups if the share is mounted locally and massive
amounts of data are copied to the share.
I.e. the system running the kernel NFS server mounts one of it's exported
shares instead of accessing the exported filesystem locally. Writing on the
share from remote hosts works fine.

For reference the line from /etc/exports:
/test 10.1.71.251(rw,sync,fsid=0,no_root_squash,no_subtree_check)
/test 10.1.71.252(rw,sync,fsid=0,no_root_squash,no_subtree_check)
/test 10.1.71.250(rw,sync,fsid=0,no_root_squash,no_subtree_check)

Disabling/enabling subtree_check and sync/async don't make a difference.
These lockups can be reproduced with 2.6.18, 2.6.20 and 2.6.22 and as it occurs
on two systems with different hardware a hardware bug seems unlikely.

The symptoms occur both with NFS4 and NFS3, although NFS3 appears more stable.

Steps to reproduce:
1. Create a /etc/exports with the line above
2. Run NFS kernel server
3. Mount the above share somewhere, e.g. /mnt/nfstest
4. Run dd if=/dev/zero of=/mnt/nfstest bs=1024k count=4048
   This should lead to a lockup pretty soon.


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