Hi Hugh,
At Sun, 20 Nov 2005 19:35:57 +0000 (GMT),
Hugh Dickins wrote:
>
> On Sun, 20 Nov 2005, Lee Revell wrote:
> > (Added alsa-devel to cc:)
> >
> > Will this change have any ill effects on older kernels?
>
> I think not (except 2.6.5 and earlier didn't define __GFP_COMP).
Sorry, I still don't figure out how __GFP_COMP solved this problem.
Could you enlighten me a bit?
Isn't it needed for dma_alloc_coherent() (for i386, particularly),
too? dma_alloc_coherent() also gets pages with __get_free_pages().
Also, I think we can remove all Set/ClearPageReserved() in memalloc.c
now. It was there just for mmap...
> > If not we should fix it in the ALSA tree right?
>
> Probably, but I'm no authority on the ALSA tree.
We'd need to add a dummy definition of __GFP_COMP for older kenels in
alsa-driver tree. But that's all.
> And suggest you wait a bit, since I haven't yet signed off on the
> patch that piece will be a part of.
>
> And what about the patch at the bottom (which I had CC'ed to Karsten
> Wiese), is that part of the ALSA tree too? That case isn't so easy:
> the get_page makes a difference, and probably it was right not to do
> it before, yet strange it was the only nopage in the tree which didn't
> get_page.
In the ealier version, get_page() in sound/pcm_native.c was checked
with "if (! PageReserved(page))". Since the pages were always
reserved, get_page was never called indeed. (IIRC, the check was
introduced to avoid crash with anon page or so.)
usx2y driver was added later, so it didn't have unneeded get_page().
thanks,
Takashi
>
> Hugh
>
> > Lee
> >
> > On Sun, 2005-11-20 at 08:05 +0000, Hugh Dickins wrote:
> > > On Sat, 19 Nov 2005, Miles Lane wrote:
> > > > [17179671.700000] Bad page state at free_hot_cold_page (in process
> > > > 'aplay', page c18eef30)
> > > > [17179671.700000] flags:0x80000414 mapping:00000000 mapcount:0 count:0
> > >
> > > Please let me know if it's not fixed by:
> > >
> > > --- 2.6.15-rc1-mm2/sound/core/memalloc.c 2005-11-12 09:01:28.000000000 +0000
> > > +++ linux/sound/core/memalloc.c 2005-11-19 19:03:32.000000000 +0000
> > > @@ -197,6 +197,7 @@ void *snd_malloc_pages(size_t size, gfp_
> > >
> > > snd_assert(size > 0, return NULL);
> > > snd_assert(gfp_flags != 0, return NULL);
> > > + gfp_flags |= __GFP_COMP; /* compound page lets parts be mapped */
> > > pg = get_order(size);
> > > if ((res = (void *) __get_free_pages(gfp_flags, pg)) != NULL) {
> > > mark_pages(virt_to_page(res), pg);
> > > @@ -241,6 +242,7 @@ static void *snd_malloc_dev_pages(struct
> > > snd_assert(dma != NULL, return NULL);
> > > pg = get_order(size);
> > > gfp_flags = GFP_KERNEL
> > > + | __GFP_COMP /* compound page lets parts be mapped */
> > > | __GFP_NORETRY /* don't trigger OOM-killer */
> > > | __GFP_NOWARN; /* no stack trace print - this call is non-critical */
> > > res = dma_alloc_coherent(dev, PAGE_SIZE << pg, dma, gfp_flags);
>
> Karsten Wiese <[email protected]>
> [PATCH 03/11] unpaged: sound nopage get_page
>
> Something noticed when studying use of VM_RESERVED in different drivers:
> snd_usX2Y_hwdep_pcm_vm_nopage omitted to get_page: fixed.
>
> And how did this work before? Aargh! That nopage is returning a page
> from within a buffer allocated by snd_malloc_pages, which allocates a
> high-order page, then does SetPageReserved on each 0-order page within.
>
> That would have worked in 2.6.14, because when the area was unmapped,
> PageReserved inhibited put_page. 2.6.15-rc1 removed that inhibition
> (while leaving ineffective PageReserveds around for now), but it hasn't
> caused trouble because.. we've not been freeing from VM_RESERVED at all.
>
> Signed-off-by: Hugh Dickins <[email protected]>
> ---
>
> sound/usb/usx2y/usx2yhwdeppcm.c | 1 +
> 1 files changed, 1 insertion(+)
>
> --- unpaged02/sound/usb/usx2y/usx2yhwdeppcm.c 2005-11-12 09:01:30.000000000 +0000
> +++ unpaged03/sound/usb/usx2y/usx2yhwdeppcm.c 2005-11-17 15:10:34.000000000 +0000
> @@ -691,6 +691,7 @@ static struct page * snd_usX2Y_hwdep_pcm
> snd_assert((offset % PAGE_SIZE) == 0, return NOPAGE_OOM);
> vaddr = (char*)((usX2Ydev_t*)area->vm_private_data)->hwdep_pcm_shm + offset;
> page = virt_to_page(vaddr);
> + get_page(page);
>
> if (type)
> *type = VM_FAULT_MINOR;
> -
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