Re: [PATCH+comment] fix tmpfs BUG and AOP_WRITEPAGE_ACTIVATE

From: Pekka Enberg
Date: Thu Oct 25 2007 - 01:37:40 EST


Hi Hugh,

On 10/25/07, Hugh Dickins <hugh@xxxxxxxxxxx> wrote:
> --- 2.6.24-rc1/mm/shmem.c 2007-10-24 07:16:04.000000000 +0100
> +++ linux/mm/shmem.c 2007-10-24 22:31:09.000000000 +0100
> @@ -915,6 +915,21 @@ static int shmem_writepage(struct page *
> struct inode *inode;
>
> BUG_ON(!PageLocked(page));
> + /*
> + * shmem_backing_dev_info's capabilities prevent regular writeback or
> + * sync from ever calling shmem_writepage; but a stacking filesystem
> + * may use the ->writepage of its underlying filesystem, in which case

I find the above bit somewhat misleading as it implies that the
!wbc->for_reclaim case can be removed after ecryptfs has similar fix
as unionfs. Can we just say that while BDI_CAP_NO_WRITEBACK does
prevent some callers from entering ->writepage(), it's just an
optimization and ->writepage() must deal with !wbc->for_reclaim case
properly?

Pekka
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