No. It is still cached. You find the buffer with "page->buffer", and when
all of them are up-to-date (whether from read-in or from having written
to them all), you just mark the whole page up-to-date.
This _works_. Try it on ext2 or NFS today.
Now, it may be that the preliminary patches from Andrea do not work this
way. I didn't look at them too closely, and I assume that Andrea basically
made the block-size be the same as the page size. That's how I would have
done it (and then waited for people to find real life cases where we want
to allow sector writes).
So in short: the page cache supports _today_ all the optimizations. In
fact, you can, on NFS, do 4096 one-byte writes, and they will be (a)
coalesced into one write over the wire, and (b) will be cached in the page
and the page marked up-to-date.
Linus
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