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Re: [Cluster-devel] [GFS2 PATCH] GFS2: Eliminate sd_rindex_mutex

----- Original Message -----
| Bearing in mind that the mutex is an exclusive lock and the glock is
| only a shared lock, do we have any other protection against the rgrp
| tree being updated simultaneously?
| Steve.


Yes, I think you're right. The existing code should work most of the
time but has the potential to leak rgrp memory if the timing is right.
We could approach the solution two ways:

(1) We could change the shared lock to an exclusive lock.
(2) We could change function rgd_insert so that it returns an error if
    the rgrp was already in the rb_tree. That way, whoever gets the
    sd_rindex_spin spinlock first will call rgd_insert to insert the new
    rgrp into the rgrp tree, and when the second caller tries to insert
    its new rgrp into the rb_tree, it will find the entry already there,
    (inserted by the first caller), then take the error path and exit,
    freeing the rgrp it kmalloced.


Bob Peterson
Red Hat File Systems

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