[PATCH 1/3] fs: Introduce new flag FALLOC_FL_COLLAPSE_RANGE

[Dave Chinner]

On Wed, Jul 31, 2013 at 06:01:54PM -0400, Theodore Ts'o wrote:
> Have you considered what happens if you have a 10 megabyte file, of
> which the first 5 megs are mmap'ed into a userspace process.
> 
> Now suppose you call COLLAPASE_RANGE on a one megabyte range starting
> at offset 1024k from the beginning of the file.
> 
> Does the right thing happen to the mmap'ed region in memory?

Implementation detail. like a hole punch, it needs to invalidate the
range that it is operating over so mmap()d regions are refaulted
after the operation is done.

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com