From mboxrd@z Thu Jan  1 00:00:00 1970
From: hooanon05@yahoo.co.jp
Subject: Re: [fuse-devel] delta filesystem prototype
Date: Tue, 03 Mar 2009 22:11:24 +0900
Message-ID: <7200.1236085884@jrobl>
References: <E1LdQOr-0008RD-25@pomaz-ex.szeredi.hu> <9884.1236069117@jrobl> <87r61ec1o7.fsf@frosties.localdomain>
Cc: Miklos Szeredi <miklos@szeredi.hu>, linux-fsdevel@vger.kernel.org,
	fuse-devel@lists.sourceforge.net
To: Goswin von Brederlow <goswin-v-b@web.de>
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Goswin von Brederlow:
> Why? When a page is accessed the filesystem gets a read request and
> reads it either from the RO branch or the delta branch. Why should it
> need to copy up the full file?

For example,
- you have two mmap for a single file
- the first mapping is done, it may map the file on the lower rdonly
  layer
- the other mapping modifies the contents
- can the first mapping see the new content?

Of course, it may depend on the implementation.


J. R. Okajima