On Wed, 1 Dec 2010 14:43:14 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
wrote:
> On Thu, 2 Dec 2010 08:29:13 +1100
> Neil Brown <neilb@xxxxxxx> wrote:
>
> > > >
> > > > However, while reading Documentation/filesystems/vfs.txt (in order to
> > > > add documentation for freepage) I was surprised to read that the
> > > > ->releasepage() is itself supposed to be allowed to actually remove the
> > > > page from the address space if it so desires.
> > >
> > > That doesn't sound right. It came from Neil in 2006.
> > >
> > > Neil, what were you thinking there? Did you find such a ->releasepage()?
> >
> > Nope, no idea, sorry.
> >
> > No releasepage functions do anything like that, and no call sites suggest it
> > could be a possibility. Quite the reverse - they are likely to remove the
> > page from the mapping without checking that it is still in the mapping.
> >
> > So that sentence should be deleted.
>
> This?
Perfect, thanks.
NeilBrown
>
> From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>
> ->releasepage() does not remove the page from the mapping.
>
> Cc: Neil Brown <neilb@xxxxxxx>
> Cc: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> Documentation/filesystems/vfs.txt | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff -puN Documentation/filesystems/vfs.txt~documentation-filesystems-vfstxt-fix-repeasepage-description Documentation/filesystems/vfs.txt
> --- a/Documentation/filesystems/vfs.txt~documentation-filesystems-vfstxt-fix-repeasepage-description
> +++ a/Documentation/filesystems/vfs.txt
> @@ -660,11 +660,10 @@ struct address_space_operations {
> releasepage: releasepage is called on PagePrivate pages to indicate
> that the page should be freed if possible. ->releasepage
> should remove any private data from the page and clear the
> - PagePrivate flag. It may also remove the page from the
> - address_space. If this fails for some reason, it may indicate
> - failure with a 0 return value.
> - This is used in two distinct though related cases. The first
> - is when the VM finds a clean page with no active users and
> + PagePrivate flag. If releasepage() fails for some reason, it must
> + indicate failure with a 0 return value.
> + releasepage() is used in two distinct though related cases. The
> + first is when the VM finds a clean page with no active users and
> wants to make it a free page. If ->releasepage succeeds, the
> page will be removed from the address_space and become free.
>
> _
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