[Ocfs2-devel] Question of rejecting a downconvert

[Dong Yang Li]

but just re-queuing the downconvert when the dentry is used as a mount point won't work for this case,
because when the other node wanna up-convert its dentry_lock to EX, it has already got the EX lock on

the inode of the dentry's parent. so when we wanna get a PR lock on the inode(this could happen during a umount on the mountpoint),
we'll block on that and both the nodes will wait for each other forever. I see two options on this:
1. make a node could reject the downconvert when it requires so.
2. blocking the other node when it wanna unlink the dentry we used as a mount point,
and make us could get a PR on the inode of the mount point's parent, so after umount
we can finally do the downconvert and unblock the other node.
Comments?
Br,
Li Dongyang

>>> Sunil Mushran  03/25/10 2:51 AM >>>
While the fs can delay the downconvert of any resource, there are
no means of explicitly rejecting it. And no rejection means the
requesting node will keep waiting for the downconvert.

Li Dongyang wrote:
> Hi, list
> I've read 
> http://opendlm.sourceforge.net/cvsmirror/opendlm/docs/dlmbook_final.pdf but 
> still confused, why a node can not reject a downconvert when it gets a bast in 
> o2dlm?
> and if we can, we could fix this bug: 
> http://oss.oracle.com/bugzilla/show_bug.cgi?id=1075
> ocfs2: a busy mount point can be removed from another node
> by adding a check in check_downconvert callback:
> if the dentry->d_mounted is not zero, then just reject the downconvert.
>
> Any hints? :-)
> Thanks
>
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