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    SubjectRe: [patch resend v4] update ctime and mtime for mmaped write
    On 27 Mar 2007 15:24:52 -0400 wrote:

    > > * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
    > Yes, I noticed. See
    > for a bug report on the subject February 2006.

    Suggest you use msync(MS_ASYNC), then

    The new (post 2.6.17) MAP_SHARED dirty-page semantics mean that the msync()
    isn't actually needed.

    > That's why this application is still running on 2.4.
    > As I mentioned at the time, the SUS says:
    > (
    > "When MS_ASYNC is specified, msync() returns immediately once all the
    > write operations are initiated or queued for servicing."
    > You can argue that putting it on the dirty list constitutes "queued for
    > servicing", but the intent seems pretty clear to me: MS_ASYNC is supposed
    > to start the I/O. Although strict standards-ese parsing says that
    > either branch of an or is acceptable, it is a common English language
    > convention that the first alternative is preferred and the second
    > is a fallback.
    > It makes sense in this case: start the write or, if that's not possible
    > (the disk is already busy), queue it for service as soon as the disk
    > is available.
    > They perhaps didn't mandate it this strictly, but that's clearly the
    > intent.

    We can fix your application, and we'll break someone else's.

    I don't think it's solveable, really - the range of applications is so
    broad, and the "standard" is so vague as to be useless. This is why we've
    been extending these things with linux-specific goodies which permit
    applications to actually tell the kernel what they want to be done in a
    more finely-grained fashion.
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