Messages in this thread | | | Date | Thu, 19 Mar 2015 22:02:52 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 05/16] page-flags: define behavior of FS/IO-related flags on compound pages |
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On Thu, Mar 19, 2015 at 11:29:52AM -0700, Dave Hansen wrote: > On 03/19/2015 10:08 AM, Kirill A. Shutemov wrote: > > The odd exception is PG_dirty: sound uses compound pages and maps them > > with PTEs. NO_COMPOUND triggers VM_BUG_ON() in set_page_dirty() on > > handling shared fault. Let's use HEAD for PG_dirty. > > Can we get the sound guys to look at this, btw? It seems like an odd > thing that we probably don't want to keep around, right?
CC: +sound guys
I'm not sure what is right fix here. At the time adding __GFP_COMP was a fix: see f3d48f0373c1.
Other odd part about __GFP_COMP here is that we have ->_mapcount in tail pages to be used for both: mapcount of the individual page and for gup pins. __compound_tail_refcounted() doesn't recognize that we don't need tail page accounting for these pages.
Hugh, I tried to ask you about the situation several times (last time on the summit). Any comments?
-- Kirill A. Shutemov
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