Re: [patch] mm: bug in set_page_dirty_buffers

[Nick Piggin <npiggin@suse.de>]

On Tue, Oct 10, 2006 at 02:07:26AM -0700, Andrew Morton wrote:
> On Tue, 10 Oct 2006 10:49:31 +0200
> Nick Piggin <npiggin@suse.de> wrote:
> 
> > > > but that is a bug in truncate and I have some patches to fix them.
> > > > 
> > > > But anyone who has done a get_user_pages, AFAIKS, can later run a
> > > > set_page_dirty on the pages.
> > > 
> > > Most (all?) callers are (and should be) using set_page_dirty_lock().
> > 
> > They don't, and I haven't checked but I doubt it is because they
> > always have the page locked.
> 
> I don't understand that.  If they're using get_user_pages() then they're probably _not_
> locking the page, and they should be using set_page_dirty_lock().
> 
> If they _are_ locking the page, and running set_page_dirty() inside that
> lock_page() then fine.

The requirement (commented fairly clearly on top of set_page_dirty_lock)
is for the mapping to be pinned, whether by page lock or some other means.

I'm not saying you're wrong because I haven't gone through everything,
have you?

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