[PATCH v2] fs/dax: deposit pagetable even when installing zero page

[Dan Williams]

On Wed, Mar 13, 2019 at 2:58 AM Jan Kara <jack at suse.cz> wrote:
>
> On Wed 13-03-19 10:17:17, Aneesh Kumar K.V wrote:
> >
> > Hi Dan/Andrew/Jan,
> >
> > "Aneesh Kumar K.V" <aneesh.kumar at linux.ibm.com> writes:
> >
> > > 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
> > >
> > > Fixes: b5beae5e224f ("powerpc/pseries: Add driver for PAPR SCM regions")
> > > Reviewed-by: Jan Kara <jack at suse.cz>
> > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> >
> > Any suggestion on which tree this patch should got to? Also since this
> > fix a kernel crash, we may want to get this to 5.1?
>
> I think this should go through Dan's tree...

I'll merge this and let it soak in -next for a week and then submit for 5.1-rc2.