Messages in this thread | | | Date | Sun, 16 Jun 2002 17:35:24 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: 2.4.18 no timestamp update on modified mmapped files |
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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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