linux-kernel - Re: [PATCH RESEND 3/10] ext4: Add support FALLOC_FL_COLLAPSE

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Message-ID: <20140218143005.GO26580@thunk.org>
Date:	Tue, 18 Feb 2014 09:30:05 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	Lukáš Czerner <lczerner@...hat.com>,
	viro@...iv.linux.org.uk, david@...morbit.com, bpm@....com,
	adilger.kernel@...ger.ca, jack@...e.cz, mtk.manpages@...il.com,
	linux-fsdevel@...r.kernel.org, xfs@....sgi.com,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Ashish Sangwan <a.sangwan@...sung.com>
Subject: Re: [PATCH RESEND 3/10] ext4: Add support FALLOC_FL_COLLAPSE_RANGE
 for fallocate

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
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