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

Dave Chinner
2013-08-01T00:23:58Z

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.