Re: [PATCH] [PATCH 4.9] staging: android: ion: fix page is NULL

[Cheng Chao <cs.os.kernel@xxxxxxxxx>]

for longterm v4.4.283, the code has checked if (!page)
   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/staging/android/ion/ion_system_heap.c?h=v4.4.283


static struct page *alloc_buffer_page(struct ion_system_heap *heap,
     struct ion_buffer *buffer,
     unsigned long order)
{
...
if (!cached) {
page = ion_page_pool_alloc(pool);
} else {
...
page = alloc_pages(gfp_flags | __GFP_COMP, order);
if (!page)    <---
   return NULL; <---

ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order,
...
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
for longterm v4.14.246, has no ion_pages_sync_for_device after
ion_page_pool_alloc
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/staging/android/ion/ion_system_heap.c?h=v4.14.246


static struct page *alloc_buffer_page(struct ion_system_heap *heap,
     struct ion_buffer *buffer,
     unsigned long order)
{
...
if (!cached)
pool = heap->uncached_pools[order_to_index(order)];
else
pool = heap->cached_pools[order_to_index(order)];

page = ion_page_pool_alloc(pool);

return page;
}

----------------------------------------------------------------------------------------------------------------------------------------------------------
after longterm v4.19.206(include),

static struct page *alloc_buffer_page(struct ion_system_heap *heap,
     struct ion_buffer *buffer,
     unsigned long order)
{
struct ion_page_pool *pool = heap->pools[order_to_index(order)];

return ion_page_pool_alloc(pool);
}

On Sat, Sep 11, 2021 at 7:54 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Sat, Sep 11, 2021 at 07:21:15PM +0800, Cheng Chao wrote:
> > kernel panic is here:
> >
> > Unable to handle kernel paging request at virtual address b0380000
> > pgd = d9d94000
> > [b0380000] *pgd=00000000
> > Internal error: Oops: 2805 [#1] PREEMPT SMP ARM
> > ...
> > task: daa2dd00 task.stack: da194000
> > PC is at v7_dma_clean_range+0x1c/0x34
> > LR is at arm_dma_sync_single_for_device+0x44/0x58
> > pc : [<c011aa0c>]    lr : [<c011645c>]    psr: 200f0013
> > sp : da195da0  ip : dc1f9000  fp : c1043dc4
> > r10: 00000000  r9 : c16f1f58  r8 : 00000001
> > r7 : c1621f94  r6 : c0116418  r5 : 00000000  r4 : c011aa58
> > r3 : 0000003f  r2 : 00000040  r1 : b0480000  r0 : b0380000
> > Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> > Control: 10c5383d  Table: 19d9406a  DAC: 00000051
> > ...
> > [<c011aa0c>] (v7_dma_clean_range) from [<c011645c>] (arm_dma_sync_single_for_device+0x44/0x58)
> > [<c011645c>] (arm_dma_sync_single_for_device) from [<c0117088>] (arm_dma_sync_sg_for_device+0x50/0x7c)
> > [<c0117088>] (arm_dma_sync_sg_for_device) from [<c0c033c4>] (ion_pages_sync_for_device+0xb0/0xec)
> > [<c0c033c4>] (ion_pages_sync_for_device) from [<c0c054ac>] (ion_system_heap_allocate+0x2a0/0x2e0)
> > [<c0c054ac>] (ion_system_heap_allocate) from [<c0c02c78>] (ion_alloc+0x12c/0x494)
> > [<c0c02c78>] (ion_alloc) from [<c0c03eac>] (ion_ioctl+0x510/0x63c)
> > [<c0c03eac>] (ion_ioctl) from [<c027c4b0>] (do_vfs_ioctl+0xa8/0x9b4)
> > [<c027c4b0>] (do_vfs_ioctl) from [<c027ce28>] (SyS_ioctl+0x6c/0x7c)
> > [<c027ce28>] (SyS_ioctl) from [<c0108a40>] (ret_fast_syscall+0x0/0x48)
> > Code: e3a02004 e1a02312 e2423001 e1c00003 (ee070f3a)
> > ---[ end trace 89278304932c0e87 ]---
> > Kernel panic - not syncing: Fatal exception
> >
> > Signed-off-by: Cheng Chao <cs.os.kernel@xxxxxxxxx>
> > ---
> >  drivers/staging/android/ion/ion_system_heap.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> > index 22c481f2ae4f..2a35b99cf628 100644
> > --- a/drivers/staging/android/ion/ion_system_heap.c
> > +++ b/drivers/staging/android/ion/ion_system_heap.c
> > @@ -75,7 +75,7 @@ static struct page *alloc_buffer_page(struct ion_system_heap *heap,
> >
> >       page = ion_page_pool_alloc(pool);
> >
> > -     if (cached)
> > +     if (page && cached)
> >               ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order,
> >                                         DMA_BIDIRECTIONAL);
> >       return page;
> > --
> > 2.26.3
> >
>
> Why is this just a 4.9 patch?  Ion didn't get removed until 5.11, so
> wouldn't this be an issue for anything 5.10 and older?
>
> thanks,
>
> greg k-h