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Date: Tue, 18 Feb 2014 09:30:05 -0500
From: "Theodore Ts'o" <tytso@mit.edu>
To: Namjae Jeon <linkinjeon@gmail.com>
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        Ashish Sangwan <a.sangwan@samsung.com>
Subject: Re: [PATCH RESEND 3/10] ext4: Add support FALLOC_FL_COLLAPSE_RANGE
 for fallocate
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Namjae,

Did you respond to Matthew Wilcox's comments/question from Feb. 2nd?

> > What if the file is mmaped at the time somebody issues this command?
> > Seems to me we should drop pagecache pages that overlap with the
> > removed blocks.  If the removed range is not a multiple of PAGE_SIZE,
> > then we should also drop any pagecache pages after the removed range.
>
> Oops, forgot to add "and if it is a multiple of page size, then we need
> to update the offsets of any pages after the removed page".

Dave responded that XFS does the right thing when doing a punch hole
operation, but it wasn't obvious to me whether FL_COLLAPSE_RANGE does
the right thing with ext4.

Thanks,

					- Ted