Re: filefrag and reflink

[Carlos Maiolino <cmaiolino@redhat.com>]

> > zeros, while a cp --reflink will create a sparse file, though?
> 
> Well see therein lies the problem.  The documentation for cp states:
> 
> "When --reflink[=always] is specified, perform a lightweight copy, where
> the data blocks are copied only when modified."
> 
> The lightest weight copy for a bunch of zeroes is a hole.  That's the
> interpretation I went with. :)
> 
> OTOH the "copied only when modified" language does sort of imply that
> you'd share the unwritten extents and then COW them, but that involves
> adding more machinery to _iomap_begin to copy-write over zeroes,
> which seems pointless and would involve a format change since old
> kernels wouldn't know to check for shared unwritten extents...
> 
> ...and if your worry is about being able to write to tmp3 without
> hitting ENOSPC then you'll have to fallocate + funshare the file
> separately anyway.

/me should read the whole thread before replying to earlier messages :P

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-- 
Carlos