On Thu, Dec 22, 2016 at 08:48:21AM +0900, Minchan Kim wrote: > Andreas reported [1] made a test in jemalloc hang in THP mode in arm64. I guess you wanted put b8d3c4c3009d before [1], right? > http://lkml.kernel.org/r/mvmmvfy37g1.fsf@xxxxxxxxxxxxxxx > > The problem is page fault handler supports only accessed flag emulation > for THP page of SW-dirty/accessed architecture. > > This patch enables dirty-bit emulation for those architectures. > Without it, MADV_FREE makes application hang by repeated fault forever. > > [1] mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called > > Cc: Jason Evans <je@xxxxxx> > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: linux-arch@xxxxxxxxxxxxxxx > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Cc: <stable@xxxxxxxxxxxxxxx> [4.5+] > Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") > Reported-by: Andreas Schwab <schwab@xxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > --- > mm/huge_memory.c | 6 ++++-- > mm/memory.c | 18 ++++++++++-------- > 2 files changed, 14 insertions(+), 10 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 10eedbf..29ec8a4 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) > { > pmd_t entry; > unsigned long haddr; > + bool write = vmf->flags & FAULT_FLAG_WRITE; > > vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); > if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) > goto unlock; > > entry = pmd_mkyoung(orig_pmd); > + if (write) > + entry = pmd_mkdirty(entry); > haddr = vmf->address & HPAGE_PMD_MASK; > - if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, > - vmf->flags & FAULT_FLAG_WRITE)) > + if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) > update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); > > unlock: > diff --git a/mm/memory.c b/mm/memory.c > index 36c774f..7408ddc 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3637,18 +3637,20 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, > if (pmd_protnone(orig_pmd) && vma_is_accessible(vma)) > return do_huge_pmd_numa_page(&vmf, orig_pmd); > > - if ((vmf.flags & FAULT_FLAG_WRITE) && > - !pmd_write(orig_pmd)) { > - ret = wp_huge_pmd(&vmf, orig_pmd); > - if (!(ret & VM_FAULT_FALLBACK)) > + if (vmf.flags & FAULT_FLAG_WRITE) { > + if (!pmd_write(orig_pmd)) { > + ret = wp_huge_pmd(&vmf, orig_pmd); > + if (ret == VM_FAULT_FALLBACK) In theory, more than one flag can be set and it would lead to false-negative. Bit check was the right thing. And I don't understand why do you need to change code in __handle_mm_fault() at all. >From what I see change to huge_pmd_set_accessed() should be enough. > + goto pte_fault; > return ret; > - } else { > - huge_pmd_set_accessed(&vmf, orig_pmd); > - return 0; > + } > } > + > + huge_pmd_set_accessed(&vmf, orig_pmd); > + return 0; > } > } > - > +pte_fault: > return handle_pte_fault(&vmf); > } > > -- > 2.7.4 > > -- > 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> -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html