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Date: Wed, 23 Nov 2011 11:07:05 -0800 (PST)
From: Hugh Dickins <hughd@google.com>
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To: Cong Wang <amwang@redhat.com>
cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        Pekka Enberg <penberg@kernel.org>, Christoph Hellwig <hch@lst.de>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Lennart Poettering <lennart@poettering.net>,
        Kay Sievers <kay.sievers@vrfy.org>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org
Subject: Re: [V3 PATCH 1/2] tmpfs: add fallocate support
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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().

Hugh