FUSE filesystems assume that SETATTR with atime is the result of utiimes()
being called. As a result, atime and mtime will be updated. This happens
with MooseFS and glusterFS. atime is supposed to be updated by the
filesystem itself when it gets read operations.
We fix the problem in SETATTR operations by
1) do not create a mtime update when we have an atime update (and vice
versa), just fill the fields to avoid the filesystem restting the
missing field to Epoch, but do not pretend we want to update it.
2) If the change is limited to atime, iscard it, as updates should be
done by READ operations
3) Kernel part of PUFFS has been fixed to make sure reads on empty file
are sent to the filesystem:
http://mail-index.netbsd.org/source-changes/2015/01/13/msg062364.html
Thanks to Tom Ivar Helbekkmo for reporting this issue.
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