Re: [PATCH 21/41] CacheFiles: Permit the page lock state to be monitored [ver #48]

[Nick Piggin]

On Saturday 04 April 2009 17:09:31 Nick Piggin wrote:
> On Saturday 04 April 2009 02:56:24 David Howells wrote:
> > Add a function to install a monitor on the page lock waitqueue for a particular
> > page, thus allowing the page being unlocked to be detected.
> > 
> > This is used by CacheFiles to detect read completion on a page in the backing
> > filesystem so that it can then copy the data to the waiting netfs page.
> 
> This is the only thing I'm still worried about in core code. The extra
> page flag (which is probably unusable for any other fs, due to its
> semantics) is an issue, but Andrew seemed like he was willing to spend
> *2* page flags on this, so I'm sure he's happy with 1.

Well that is to say it is not a such a bad concept to have... actually
we already have exactly this concept which is what should be used. Ie.
the filesystem's io completion handler.
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