On Sat 24-12-16 00:14:58, Minchan Kim wrote: > Andreas reported [1] made a test in jemalloc hang in THP mode in arm64. > http://lkml.kernel.org/r/mvmmvfy37g1.fsf@xxxxxxxxxxxxxxx > > The problem is currently page fault handler doesn't supports dirty bit > emulation of pmd for non-HW dirty-bit architecture so that application > stucks until VM marked the pmd dirty. > > How the emulation work depends on the architecture. In case of arm64, > when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to > mark the pte dirty via triggering page fault when store access happens. > Once the page fault occurs, VM marks the pmd dirty and arch code for > setting pmd will clear PTE_RDONLY for application to proceed. > > IOW, if VM doesn't mark the pmd dirty, application hangs forever by > repeated fault(i.e., store op but the pmd is PTE_RDONLY). > > This patch enables pmd dirty-bit emulation for those architectures. Thanks for extending the patch description again! > [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called > > Cc: Jason Evans <je@xxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > 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-and-Tested-by: Andreas Schwab <schwab@xxxxxxx> > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > Merry Xmas! > > * from v3 > * Elaborate description > * from v2 > * Add acked-by/tested-by > * from v1 > * Remove __handle_mm_fault part - Kirill > mm/huge_memory.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 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: > -- > 2.7.4 > -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
