| Message ID | 20181213051510.20306-1-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] mm: thp: fix flags for pmd migration when split | expand |
On Thu, Dec 13, 2018 at 8:15 AM Peter Xu <peterx@redhat.com> wrote: > > When splitting a huge migrating PMD, we'll transfer all the existing > PMD bits and apply them again onto the small PTEs. However we are > fetching the bits unconditionally via pmd_soft_dirty(), pmd_write() > or pmd_yound() while actually they don't make sense at all when it's > a migration entry. Fix them up. Since at it, drop the ifdef together > as not needed. > > Note that if my understanding is correct about the problem then if > without the patch there is chance to lose some of the dirty bits in > the migrating pmd pages (on x86_64 we're fetching bit 11 which is part > of swap offset instead of bit 2) and it could potentially corrupt the > memory of an userspace program which depends on the dirty bit. > Looks good to me Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > CC: Andrea Arcangeli <aarcange@redhat.com> > CC: Andrew Morton <akpm@linux-foundation.org> > CC: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > CC: Matthew Wilcox <willy@infradead.org> > CC: Michal Hocko <mhocko@suse.com> > CC: Dave Jiang <dave.jiang@intel.com> > CC: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> > CC: Souptick Joarder <jrdr.linux@gmail.com> > CC: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > CC: Zi Yan <zi.yan@cs.rutgers.edu> > CC: linux-mm@kvack.org > CC: linux-kernel@vger.kernel.org > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > v2: > - fix it up for young/write/dirty bits too [Konstantin] > v3: > - fetch write correctly for migration entry; drop macro [Konstantin] > --- > mm/huge_memory.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index f2d19e4fe854..aebade83cec9 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2145,23 +2145,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > */ > old_pmd = pmdp_invalidate(vma, haddr, pmd); > > -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > pmd_migration = is_pmd_migration_entry(old_pmd); > - if (pmd_migration) { > + if (unlikely(pmd_migration)) { > swp_entry_t entry; > > entry = pmd_to_swp_entry(old_pmd); > page = pfn_to_page(swp_offset(entry)); > - } else > -#endif > + write = is_write_migration_entry(entry); > + young = false; > + soft_dirty = pmd_swp_soft_dirty(old_pmd); > + } else { > page = pmd_page(old_pmd); > + if (pmd_dirty(old_pmd)) > + SetPageDirty(page); > + write = pmd_write(old_pmd); > + young = pmd_young(old_pmd); > + soft_dirty = pmd_soft_dirty(old_pmd); > + } > VM_BUG_ON_PAGE(!page_count(page), page); > page_ref_add(page, HPAGE_PMD_NR - 1); > - if (pmd_dirty(old_pmd)) > - SetPageDirty(page); > - write = pmd_write(old_pmd); > - young = pmd_young(old_pmd); > - soft_dirty = pmd_soft_dirty(old_pmd); > > /* > * Withdraw the table only after we mark the pmd entry invalid. > -- > 2.17.1 >
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index f2d19e4fe854..aebade83cec9 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2145,23 +2145,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > */ > old_pmd = pmdp_invalidate(vma, haddr, pmd); > > -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > pmd_migration = is_pmd_migration_entry(old_pmd); > - if (pmd_migration) { > + if (unlikely(pmd_migration)) { > swp_entry_t entry; > > entry = pmd_to_swp_entry(old_pmd); > page = pfn_to_page(swp_offset(entry)); > - } else > -#endif > + write = is_write_migration_entry(entry); > + young = false; > + soft_dirty = pmd_swp_soft_dirty(old_pmd); > + } else { > page = pmd_page(old_pmd); > + if (pmd_dirty(old_pmd)) > + SetPageDirty(page); > + write = pmd_write(old_pmd); > + young = pmd_young(old_pmd); > + soft_dirty = pmd_soft_dirty(old_pmd); > + } > VM_BUG_ON_PAGE(!page_count(page), page); > page_ref_add(page, HPAGE_PMD_NR - 1); > - if (pmd_dirty(old_pmd)) > - SetPageDirty(page); > - write = pmd_write(old_pmd); > - young = pmd_young(old_pmd); > - soft_dirty = pmd_soft_dirty(old_pmd); > > /* > * Withdraw the table only after we mark the pmd entry invalid. > -- Looks good. Reviewed-by: William Kucharski <william.kucharski@oracle.com>
On Thu, Dec 13, 2018 at 01:15:10PM +0800, Peter Xu wrote: > When splitting a huge migrating PMD, we'll transfer all the existing > PMD bits and apply them again onto the small PTEs. However we are > fetching the bits unconditionally via pmd_soft_dirty(), pmd_write() > or pmd_yound() while actually they don't make sense at all when it's > a migration entry. Fix them up. Since at it, drop the ifdef together > as not needed. > > Note that if my understanding is correct about the problem then if > without the patch there is chance to lose some of the dirty bits in > the migrating pmd pages (on x86_64 we're fetching bit 11 which is part > of swap offset instead of bit 2) and it could potentially corrupt the > memory of an userspace program which depends on the dirty bit. > > CC: Andrea Arcangeli <aarcange@redhat.com> > CC: Andrew Morton <akpm@linux-foundation.org> > CC: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > CC: Matthew Wilcox <willy@infradead.org> > CC: Michal Hocko <mhocko@suse.com> > CC: Dave Jiang <dave.jiang@intel.com> > CC: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> > CC: Souptick Joarder <jrdr.linux@gmail.com> > CC: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > CC: Zi Yan <zi.yan@cs.rutgers.edu> > CC: linux-mm@kvack.org > CC: linux-kernel@vger.kernel.org > Signed-off-by: Peter Xu <peterx@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Stable?
On Thu, Dec 13, 2018 at 12:59:42PM +0300, Kirill A. Shutemov wrote: > On Thu, Dec 13, 2018 at 01:15:10PM +0800, Peter Xu wrote: > > When splitting a huge migrating PMD, we'll transfer all the existing > > PMD bits and apply them again onto the small PTEs. However we are > > fetching the bits unconditionally via pmd_soft_dirty(), pmd_write() > > or pmd_yound() while actually they don't make sense at all when it's > > a migration entry. Fix them up. Since at it, drop the ifdef together > > as not needed. > > > > Note that if my understanding is correct about the problem then if > > without the patch there is chance to lose some of the dirty bits in > > the migrating pmd pages (on x86_64 we're fetching bit 11 which is part > > of swap offset instead of bit 2) and it could potentially corrupt the > > memory of an userspace program which depends on the dirty bit. > > > > CC: Andrea Arcangeli <aarcange@redhat.com> > > CC: Andrew Morton <akpm@linux-foundation.org> > > CC: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > > CC: Matthew Wilcox <willy@infradead.org> > > CC: Michal Hocko <mhocko@suse.com> > > CC: Dave Jiang <dave.jiang@intel.com> > > CC: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> > > CC: Souptick Joarder <jrdr.linux@gmail.com> > > CC: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > > CC: Zi Yan <zi.yan@cs.rutgers.edu> > > CC: linux-mm@kvack.org > > CC: linux-kernel@vger.kernel.org > > Signed-off-by: Peter Xu <peterx@redhat.com> > > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > Stable? Sorry I missed the reply from Zi. I think it should be: CC: linux-stable <stable@vger.kernel.org> # 4.14+ Thanks,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f2d19e4fe854..aebade83cec9 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2145,23 +2145,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, */ old_pmd = pmdp_invalidate(vma, haddr, pmd); -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION pmd_migration = is_pmd_migration_entry(old_pmd); - if (pmd_migration) { + if (unlikely(pmd_migration)) { swp_entry_t entry; entry = pmd_to_swp_entry(old_pmd); page = pfn_to_page(swp_offset(entry)); - } else -#endif + write = is_write_migration_entry(entry); + young = false; + soft_dirty = pmd_swp_soft_dirty(old_pmd); + } else { page = pmd_page(old_pmd); + if (pmd_dirty(old_pmd)) + SetPageDirty(page); + write = pmd_write(old_pmd); + young = pmd_young(old_pmd); + soft_dirty = pmd_soft_dirty(old_pmd); + } VM_BUG_ON_PAGE(!page_count(page), page); page_ref_add(page, HPAGE_PMD_NR - 1); - if (pmd_dirty(old_pmd)) - SetPageDirty(page); - write = pmd_write(old_pmd); - young = pmd_young(old_pmd); - soft_dirty = pmd_soft_dirty(old_pmd); /* * Withdraw the table only after we mark the pmd entry invalid.
When splitting a huge migrating PMD, we'll transfer all the existing PMD bits and apply them again onto the small PTEs. However we are fetching the bits unconditionally via pmd_soft_dirty(), pmd_write() or pmd_yound() while actually they don't make sense at all when it's a migration entry. Fix them up. Since at it, drop the ifdef together as not needed. Note that if my understanding is correct about the problem then if without the patch there is chance to lose some of the dirty bits in the migrating pmd pages (on x86_64 we're fetching bit 11 which is part of swap offset instead of bit 2) and it could potentially corrupt the memory of an userspace program which depends on the dirty bit. CC: Andrea Arcangeli <aarcange@redhat.com> CC: Andrew Morton <akpm@linux-foundation.org> CC: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> CC: Matthew Wilcox <willy@infradead.org> CC: Michal Hocko <mhocko@suse.com> CC: Dave Jiang <dave.jiang@intel.com> CC: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> CC: Souptick Joarder <jrdr.linux@gmail.com> CC: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> CC: Zi Yan <zi.yan@cs.rutgers.edu> CC: linux-mm@kvack.org CC: linux-kernel@vger.kernel.org Signed-off-by: Peter Xu <peterx@redhat.com> --- v2: - fix it up for young/write/dirty bits too [Konstantin] v3: - fetch write correctly for migration entry; drop macro [Konstantin] --- mm/huge_memory.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)