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    SubjectRe: Q: generic_file_write sets PG_locked???

    On 21 Apr 1999 19:46:21 -0500, (Eric W. Biederman) said:

    > As note on the PG_locked flag.
    > That simply indicates that there is I/O inprocess on the page and you
    > can use wait_on_page to wait for it to complete.

    > This does not prevent pages from being mapped.

    > If we count on PageLocked from keeping a page from being mapped in
    > while it is being written out, I think that is a part of the current
    > NFS design that needs to be redesigned.

    Yes and no. PageLocked may just indicate a background writeback in
    progress. That definitely happens in the swap cache right now, but the
    vfs code doesn't use it for the page cache (yet). It will do. However,
    if a given filesystem provides its own write-page strategy functions
    which have their own locking semantics, there's no real reason to
    prevent it from doing so as long as the page mapping functions continue
    to block on a non-uptodate page.

    > I'm not prepared quite yet, for a large discussion on the code as I
    > haven't finished testing my prototypes. Once that is done I'll write
    > up some documentation and start pushing for integration of generic
    > dirty page handling for 2.3

    _Good_. :)


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