Re: [PATCH 1/2] fs/dax: deposit pagetable even when installing zero page

[Aneesh Kumar K.V]

On 2/28/19 2:51 PM, Jan Kara wrote:
> On Thu 28-02-19 14:05:21, Aneesh Kumar K.V wrote:
> > Architectures like ppc64 use the deposited page table to store hardware
> > page table slot information. Make sure we deposit a page table when
> > using zero page at the pmd level for hash.
> >
> > Without this we hit
> >
> > Unable to handle kernel paging request for data at address 0x00000000
> > Faulting instruction address: 0xc000000000082a74
> > Oops: Kernel access of bad area, sig: 11 [#1]
> > ....
> >
> > NIP [c000000000082a74] __hash_page_thp+0x224/0x5b0
> > LR [c0000000000829a4] __hash_page_thp+0x154/0x5b0
> > Call Trace:
> >   hash_page_mm+0x43c/0x740
> >   do_hash_page+0x2c/0x3c
> >   copy_from_iter_flushcache+0xa4/0x4a0
> >   pmem_copy_from_iter+0x2c/0x50 [nd_pmem]
> >   dax_copy_from_iter+0x40/0x70
> >   dax_iomap_actor+0x134/0x360
> >   iomap_apply+0xfc/0x1b0
> >   dax_iomap_rw+0xac/0x130
> >   ext4_file_write_iter+0x254/0x460 [ext4]
> >   __vfs_write+0x120/0x1e0
> >   vfs_write+0xd8/0x220
> >   SyS_write+0x6c/0x110
> >   system_call+0x3c/0x130
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
>
> Thanks for the patch. It looks good to me. You can add:
>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
>
> > ---
> > TODO:
> > * Add fixes tag
>
> Probably this is a problem since initial PPC PMEM support, isn't it?

Considering ppc64 is the only broken architecture here, I guess I will 
use the commit that enabled PPC PMEM support here.

-aneesh