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

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Message-ID: <CAKYAXd9E41d2Kt+Sz-d3toUFUrTLtjrOYqq32NQViM_abRWTxg@mail.gmail.com>
Date:	Wed, 19 Feb 2014 10:08:39 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Namjae Jeon <linkinjeon@...il.com>,
	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

2014-02-18 23:30 GMT+09:00, Theodore Ts'o <tytso@....edu>:
> Namjae,
Hi Ted.
>
> Did you respond to Matthew Wilcox's comments/question from Feb. 2nd?
Sorry, I didn't catch about this.
I just replied from Matthew's mail.
Thanks for your remind.
>
>> > 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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