> Hmm? Look at the page_cache_read() code more closely:
> add_to_page_cache_unique() calls __add_to_page_cache, which
> sets up the new page to be locked.
> The locking is not quite so visible now, but it is still there.
> Indeed, the locking is now done at the lower level precisely so
> that we can be 100% sure that a page which has been newly added
> to the page cache and which does not yet have valid contents is
> guaranteed to be both locked and !uptodate, so that nobody will
> ever look at the contents before they have been initialised.
Yup. I found that out the hard way (lockups). It's been corrected
now. I still found the io-flag useful though for serializing writing
to pages and actually syncing those same pages to the server.
Cheers,
Trond
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