linux-kernel - Re: [V3 PATCH 1/2] tmpfs: add fallocate support

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Message-ID: <4ECDB778.30006@redhat.com>
Date:	Thu, 24 Nov 2011 11:18:16 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Hugh Dickins <hughd@...gle.com>
CC:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Pekka Enberg <penberg@...nel.org>,
	Christoph Hellwig <hch@....de>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Lennart Poettering <lennart@...ttering.net>,
	Kay Sievers <kay.sievers@...y.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-mm@...ck.org
Subject: Re: [V3 PATCH 1/2] tmpfs: add fallocate support

于 2011年11月24日 03:07, Hugh Dickins 写道:
> On Wed, 23 Nov 2011, Cong Wang wrote:
>> +
>> +	while (index<  end) {
>> +		ret = shmem_getpage(inode, index,&page, SGP_WRITE, NULL);
>> +		if (ret) {
>> +			if (ret == -ENOSPC)
>> +				goto undo;
> ...
>> +undo:
>> +	while (index>  start) {
>> +		shmem_truncate_page(inode, index);
>> +		index--;
>> +	}
>
> As I said before, I won't actually be reviewing and testing this for
> a week or two; but before this goes any further, must point out how
> wrong it is.  Here you'll be deleting any pages in the range that were
> already present before the failing fallocate().

Ah, I totally missed this. So, is there any way to tell if the page
gotten from shmem_getpage() is newly allocated or not?

I will dig the code...

Thanks.
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