On Sun, 16 Jun 2002, Kevin Easton wrote:
>
> So... the difference on i386 is just the definitions of the protection_map
> entries that are used.. specifically that PAGE_SHARED in asm-i386/pgtable.h
> includes _PAGE_RW? Changing this definition to be the same as the PAGE_COPY
> definition would be one fix?
It _could_ be _part_ of a fix (to the "problem" of dirty unbacked
pages arriving unheralded at the filesystem, too late to find
space for them; but our reluctance to have read faults allocate).
I say "could" because it would tend to cause double (read then write)
faulting more widely than necessary; I say "part" because at present
do_wp_page expects to be handling private Copy-On-Write faults rather
than shared mappings (please correct me if I'm wrong, Russell); and
we would still need to implement a callout down to the filesystem
(e.g. "wppage" method I suggested) to allocate the space (though,
doing it on the cheap, that method could be "nopage" revisited).
And I put quotes around "problem" because I'm uncertain how seriously
to take it, and we've had no chorus of anxious developers and users.
Hugh
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This archive was generated by hypermail 2b29 : Sun Jun 23 2002 - 22:00:11 EST