On Wed, 2014-01-01 at 15:23 +0530, Aneesh Kumar K.V wrote: > From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > > This patch fix the below crash > > NIP [c00000000004cee4] .__hash_page_thp+0x2a4/0x440 > LR [c0000000000439ac] .hash_page+0x18c/0x5e0 > ... > Call Trace: > [c000000736103c40] [00001ffffb000000] 0x1ffffb000000(unreliable) > [437908.479693] [c000000736103d50] [c0000000000439ac] .hash_page+0x18c/0x5e0 > [437908.479699] [c000000736103e30] [c00000000000924c] .do_hash_page+0x4c/0x58 > > On ppc64 we use the pgtable for storing the hpte slot information and > store address to the pgtable at a constant offset (PTRS_PER_PMD) from > pmd. On mremap, when we switch the pmd, we need to withdraw and deposit > the pgtable again, so that we find the pgtable at PTRS_PER_PMD offset > from new pmd. > > We also want to move the withdraw and deposit before the set_pmd so > that, when page fault find the pmd as trans huge we can be sure that > pgtable can be located at the offset. > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > --- > NOTE: > For other archs we would just be removing the pgtable from the list and adding it back. > I didn't find an easy way to make it not do that without lots of #ifdef around. Any > suggestion around that is welcome. What about - if (new_ptl != old_ptl) { + if (new_ptl != old_ptl || ARCH_THP_MOVE_PMD_ALWAYS_WITHDRAW) { Or something similar ? Cheers, Ben. > mm/huge_memory.c | 21 ++++++++++----------- > 1 file changed, 10 insertions(+), 11 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 7de1bf85f683..eb2e60d9ba45 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1500,24 +1500,23 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, > */ > ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); > if (ret == 1) { > + pgtable_t pgtable; > + > new_ptl = pmd_lockptr(mm, new_pmd); > if (new_ptl != old_ptl) > spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); > pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); > VM_BUG_ON(!pmd_none(*new_pmd)); > + /* > + * Archs like ppc64 use pgtable to store per pmd > + * specific information. So when we switch the pmd, > + * we should also withdraw and deposit the pgtable > + */ > + pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); > + pgtable_trans_huge_deposit(mm, new_pmd, pgtable); > set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); > - if (new_ptl != old_ptl) { > - pgtable_t pgtable; > - > - /* > - * Move preallocated PTE page table if new_pmd is on > - * different PMD page table. > - */ > - pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); > - pgtable_trans_huge_deposit(mm, new_pmd, pgtable); > - > + if (new_ptl != old_ptl) > spin_unlock(new_ptl); > - } > spin_unlock(old_ptl); > } > out: -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>