remount-ro & umount & quota interaction

[Michael Tokarev]

For a long time I'm bitten by a bad interaction
of mount -o remount,ro and quota operations.

The sequence is as follows:

 mount /fs
 quotaon -ug /fs
 mount -o remount,ro /fs
 umount /fs

At this point, umount never returns.  /proc/$pid/wchan
shows vfs_quota_off:

Feb  6 20:53:25 linux kernel: umount        D e5183eb8     0  8646      1
Feb  6 20:53:25 linux kernel:        e5183ecc 00000086 00000002 e5183eb8 e5183eb0 00000000 c1db2540 c1db2684
Feb  6 20:53:25 linux kernel:        c1db2684 c1c0dd00 00000000 cfd9f1c0 c0367080 c0367080 f5849000 f7f06880
Feb  6 20:53:25 linux kernel:        f7e89d80 00000000 c0367080 b7c9795c 005f3997 00000000 000000ff 00000000
Feb  6 20:53:25 linux kernel: Call Trace:
Feb  6 20:53:25 linux kernel:  [<c01a2a65>] vfs_quota_off+0x345/0x490
Feb  6 20:53:25 linux kernel:  [<c013a3a0>] autoremove_wake_function+0x0/0x50
Feb  6 20:53:25 linux kernel:  [<c0174bf6>] deactivate_super+0x46/0x80
Feb  6 20:53:25 linux kernel:  [<c0188bba>] sys_umount+0x4a/0x240
Feb  6 20:53:25 linux kernel:  [<c017637f>] sys_stat64+0xf/0x30
Feb  6 20:53:25 linux kernel:  [<c0162069>] remove_vma+0x39/0x50
Feb  6 20:53:25 linux kernel:  [<c0162b67>] do_munmap+0x197/0x1f0
Feb  6 20:53:25 linux kernel:  [<c0188dc5>] sys_oldumount+0x15/0x20
Feb  6 20:53:25 linux kernel:  [<c010417e>] sysenter_past_esp+0x5f/0x85

The filesystem is ext3.  The issue is here for a long time,
at least since before 2.6.20, and is still present in 2.6.23
(I'll try 2.6.24 later today).

Can it be fixed please? :)

Thanks!

/mjt
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