Re: [PATCH] cowlinks v2

[Jamie Lokier]

Jörn Engel wrote:
> Sharing the page cache is more important to me than sharing disk
> space.  Disk space is cheap, but increasing memory beyond 1GiB in my
> notebook is not and 1GiB is too little, so memory is the real
> constraint.

Lucky you!  I have 192MB, that's as much as it can take.

> And it looks like Pavel already found the solution.  Whenever doing
> something fishy that would confuse the page cache, we
> 1. lock
> 2. invalidate page cache for all files belonging to that cow entity
> 3. copyfile(), write(), or whatever
> 4. unlock
> 
> This is always possibly, because page cache for cow-files is never
> read-write.  If it was, we would have done 1-4 before and now have a
> regular (non-cow) file.
> 
> Did I miss something?

Just some interesting indirection or substitution of address_space
objects needed in the vmas, to map the right pages.

-- Jamie
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