[Ocfs2-tools-commits] branch, daemon-fixups, created. ocfs2-tools-1.4.0-136-g71bdcce

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        at  71bdccedf747073b0e060a7ee1afcf09bae28582 (commit)

- Log -----------------------------------------------------------------
commit 71bdccedf747073b0e060a7ee1afcf09bae28582
Author: Joel Becker <joel.becker at oracle.com>
Date:   Sat Aug 16 02:35:13 2008 -0700

    ocfs2_controld: Fix double-leave in complete_mount().
    
    In commit f5032771bc41bf9ff31ed42f332d8ec8def39e55 (ocfs2_controld: Allow
    multiple real mounts.) we stopped tracking mountpoints.  Instead, we
    describe different applications as "services".  "tunefs.ocfs2" is one
    service.  "fsck.ocfs2" is another.  The actual filesystem uses the
    service "ocfs2".
    
    Only one instance of a service is allowed, except for the filesystem.
    You can, of course, have one device mounted at multiple mountpoints:
    
     # mount /dev/sdb1 /ocfs2
     # mount /dev/sdb1 /ocfs3
    
    In the special case of the "ocfs2" service, ocfs2_controld will allow
    more than one MOUNT call (send by o2cb_begin_group_join).
    The additinaly mounters get EALREADY, which libo2cb knows to interpret
    as success.  It goes like this:
    
    mount.ocfs2 on /ocfs2 (first)		ocfs2_controld
    -----------------------------		--------------
    o2cb_begin_group_join(uuid)
    					start_join(uuid)
    					finish_join(uuid)
    					dlmcontrol_register(uuid)
    					notify_mount_client(0)
    err = mount(dev, mntpnt)
    o2cb_complete_group_join(uuid, err)
    					complete_mount(uuid, err)
    
    mount.ocfs2 on /ocfs3 (additional)	ocfs2_controld
    ----------------------------------	--------------
    o2cb_begin_group_join(uuid)
    					notify_client(EALREADY)
    err = mount(dev, mntpnt)
    o2cb_complete_group_join(uuid, err)
    					complete_mount(uuid, err)
    
    Here's the crux of the problem.  If that first mounter gets an error
    from mount(2), the daemon's complete_mount() should leave the group.
    There's no filesystem mounted.
    
    However, if the *second* mounter gets an error from mount(2) (say, a
    missing mountpoint), the daemon should not leave the group - that first
    mount is still going!  That's the bug.  The daemon didn't know the
    difference, and it would leave the group.  The first mount was left out
    in the lurch.
    
    The fix is to mark the additional mounts as such.  complete_mount()
    notices the additional flag and does nothing beyond responding to
    mount.ocfs2(8).
    
    dead_mounter() had the same problem.  If an additional mounter died, it
    was treated like a first mounter.  dead_mounter() now does what
    complete_mount() does.  It cleans up the additional state and nothing
    else.
    
    While we're there, we've learned enough about our state to handle first
    mounts that died before sending their status to the daemon.  We've
    always known that a dead_mounter() during group join could just set
    leave_on_join.  But if the mount program has already been notified,
    there may be a mounted filesystem.  We pinned the filesystem as busy and
    basically locked out all other operations.
    
    But as it turns out, a fully operational group is a good state.  We can
    clear the in-progress flag and allow new operations.  Additional mounts
    can happen cleanly, and umounts as well.  If the filesystem never got
    mounted, a cleanup with ocfs2_hb_ctl is safe.  It's up to the
    administrator to check safety, but it's a predictable environment.
    
    Signed-off-by: Joel Becker <joel.becker at oracle.com>

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