[svn-r11470] Purpose:

Repair synchronization bug in the metadata cache in PHDF5

Also repair numerous other bugs that surfaced in testing the
bug fix.


Description:

While operations modifying metadata must be collective, we allow
independant reads.  This allows metadata caches on different processes
to adjust to different sizes, and to place the entries on their dirty
lists in different orders.  Since only process 0 actually writes
metadata to disk (all other processes thought they did, but the writes
were discarded on the theory that they had to be collective), this made
it possible for another process to modify metadata, flush it, and then
read it back in in its original form (pre-modification) form.  The
possibilities for file corruption should be obvious.


Solution:

Make the policy that only process 0 can write to file explicit, and
visible to the metadata caches.  Thus only process 0 may flush dirty
entries -- all other caches must retain dirty entries until they are
informed by process 0 that the entries are clean.

Synchronization is handled by counting the bytes of dirty cache entries
created, and then synching up between the caches whenever the sum
exceeds an (eventually user specified) limit.  Dirty metadata creation
is consistent across all processes because all operations modifying
metadata must be collective.

This change uncovered may bugs which are repaired in this checkin.
It also required modification of H5HL and H5O to allocate file space
on insertion rather than on flush from cache.


Platforms tested:

H5committest, heping(parallel & serial)

Misc. update:

0 files changed, 0 insertions, 0 deletions