MS_ASYNC is not supposed to wait, so SYNC_FILE_RANGE_WAIT_BEFORE
probably should not be used in that case.
What would be perfect, is if we had a sync mode, that on encountering
a page currently under writeback, would just do a page_mkclean() on
it, so we still receive a page fault next time one of the mappings is
dirtied, so the times can be updated.
Would there be any difficulties with that?
Miklos
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