Re: [PATCH v7 08/22] Replace xip_truncate_page with dax_truncate_page

From: Matthew Wilcox
Date: Sun Apr 13 2014 - 18:38:12 EST


On Wed, Apr 09, 2014 at 11:26:35AM +0200, Jan Kara wrote:
> I thought about this for a while and classical IO, truncation etc. could
> easily work for blocksize < pagesize. And for mmap() you could just use
> pagecache. Not sure if it's worth the complications though. Anyway we
> should decide whether we don't care about blocksize < PAGE_CACHE_SIZE at
> all, or whether we try to make things which can work reasonably easily
> functional. In that case dax_truncate_page() needs some tweaking because it
> currently assumes blocksize == PAGE_CACHE_SIZE.

I think it actually assumes that blocksize <= PAGE_CACHE_SIZE in that
it doesn't contain a loop to iterate over all blocks. It wouldn't be
hard to fix but I'll just put in a comment noting what needs to be fixed
... I don't think there's going to be a lot of enthusiasm for adding
support for blocksize != PAGE_SIZE / PAGE_CACHE_SIZE.
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