diff mbox series

[v2,2/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when migration

Message ID 1ec8a987be1a5400e077260a300d0079564b1472.1652002221.git.baolin.wang@linux.alibaba.com (mailing list archive)
State New
Headers show
Series Fix CONT-PTE/PMD size hugetlb issue when unmapping or migrating | expand

Commit Message

Baolin Wang May 8, 2022, 9:36 a.m. UTC
On some architectures (like ARM64), it can support CONT-PTE/PMD size
hugetlb, which means it can support not only PMD/PUD size hugetlb:
2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page
size specified.

When migrating a hugetlb page, we will get the relevant page table
entry by huge_pte_offset() only once to nuke it and remap it with
a migration pte entry. This is correct for PMD or PUD size hugetlb,
since they always contain only one pmd entry or pud entry in the
page table.

However this is incorrect for CONT-PTE and CONT-PMD size hugetlb,
since they can contain several continuous pte or pmd entry with
same page table attributes. So we will nuke or remap only one pte
or pmd entry for this CONT-PTE/PMD size hugetlb page, which is
not expected for hugetlb migration. The problem is we can still
continue to modify the subpages' data of a hugetlb page during
migrating a hugetlb page, which can cause a serious data consistent
issue, since we did not nuke the page table entry and set a
migration pte for the subpages of a hugetlb page.

To fix this issue, we should change to use huge_ptep_clear_flush()
to nuke a hugetlb page table, and remap it with set_huge_pte_at()
and set_huge_swap_pte_at() when migrating a hugetlb page, which
already considered the CONT-PTE or CONT-PMD size hugetlb.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/rmap.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

Comments

kernel test robot May 8, 2022, 12:01 p.m. UTC | #1
Hi Baolin,

I love your patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on next-20220506]
[cannot apply to hnaz-mm/master arm64/for-next/core linus/master v5.18-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Baolin-Wang/Fix-CONT-PTE-PMD-size-hugetlb-issue-when-unmapping-or-migrating/20220508-174036
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: x86_64-randconfig-a013 (https://download.01.org/0day-ci/archive/20220508/202205081910.mStoC5rj-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/907981b27213707fdb2f8a24c107d6752a09a773
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Baolin-Wang/Fix-CONT-PTE-PMD-size-hugetlb-issue-when-unmapping-or-migrating/20220508-174036
        git checkout 907981b27213707fdb2f8a24c107d6752a09a773
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   mm/rmap.c: In function 'try_to_migrate_one':
>> mm/rmap.c:1931:34: error: implicit declaration of function 'huge_ptep_clear_flush'; did you mean 'ptep_clear_flush'? [-Werror=implicit-function-declaration]
    1931 |                         pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
         |                                  ^~~~~~~~~~~~~~~~~~~~~
         |                                  ptep_clear_flush
>> mm/rmap.c:1931:34: error: incompatible types when assigning to type 'pte_t' from type 'int'
>> mm/rmap.c:2023:41: error: implicit declaration of function 'set_huge_pte_at'; did you mean 'set_huge_swap_pte_at'? [-Werror=implicit-function-declaration]
    2023 |                                         set_huge_pte_at(mm, address, pvmw.pte, pteval);
         |                                         ^~~~~~~~~~~~~~~
         |                                         set_huge_swap_pte_at
   cc1: some warnings being treated as errors


vim +1931 mm/rmap.c

  1883	
  1884			/* Unexpected PMD-mapped THP? */
  1885			VM_BUG_ON_FOLIO(!pvmw.pte, folio);
  1886	
  1887			subpage = folio_page(folio,
  1888					pte_pfn(*pvmw.pte) - folio_pfn(folio));
  1889			address = pvmw.address;
  1890			anon_exclusive = folio_test_anon(folio) &&
  1891					 PageAnonExclusive(subpage);
  1892	
  1893			if (folio_test_hugetlb(folio)) {
  1894				/*
  1895				 * huge_pmd_unshare may unmap an entire PMD page.
  1896				 * There is no way of knowing exactly which PMDs may
  1897				 * be cached for this mm, so we must flush them all.
  1898				 * start/end were already adjusted above to cover this
  1899				 * range.
  1900				 */
  1901				flush_cache_range(vma, range.start, range.end);
  1902	
  1903				if (!folio_test_anon(folio)) {
  1904					/*
  1905					 * To call huge_pmd_unshare, i_mmap_rwsem must be
  1906					 * held in write mode.  Caller needs to explicitly
  1907					 * do this outside rmap routines.
  1908					 */
  1909					VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
  1910	
  1911					if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
  1912						flush_tlb_range(vma, range.start, range.end);
  1913						mmu_notifier_invalidate_range(mm, range.start,
  1914									      range.end);
  1915	
  1916						/*
  1917						 * The ref count of the PMD page was dropped
  1918						 * which is part of the way map counting
  1919						 * is done for shared PMDs.  Return 'true'
  1920						 * here.  When there is no other sharing,
  1921						 * huge_pmd_unshare returns false and we will
  1922						 * unmap the actual page and drop map count
  1923						 * to zero.
  1924						 */
  1925						page_vma_mapped_walk_done(&pvmw);
  1926						break;
  1927					}
  1928				}
  1929	
  1930				/* Nuke the hugetlb page table entry */
> 1931				pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
  1932			} else {
  1933				flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
  1934				/* Nuke the page table entry. */
  1935				pteval = ptep_clear_flush(vma, address, pvmw.pte);
  1936			}
  1937	
  1938			/* Set the dirty flag on the folio now the pte is gone. */
  1939			if (pte_dirty(pteval))
  1940				folio_mark_dirty(folio);
  1941	
  1942			/* Update high watermark before we lower rss */
  1943			update_hiwater_rss(mm);
  1944	
  1945			if (folio_is_zone_device(folio)) {
  1946				unsigned long pfn = folio_pfn(folio);
  1947				swp_entry_t entry;
  1948				pte_t swp_pte;
  1949	
  1950				if (anon_exclusive)
  1951					BUG_ON(page_try_share_anon_rmap(subpage));
  1952	
  1953				/*
  1954				 * Store the pfn of the page in a special migration
  1955				 * pte. do_swap_page() will wait until the migration
  1956				 * pte is removed and then restart fault handling.
  1957				 */
  1958				entry = pte_to_swp_entry(pteval);
  1959				if (is_writable_device_private_entry(entry))
  1960					entry = make_writable_migration_entry(pfn);
  1961				else if (anon_exclusive)
  1962					entry = make_readable_exclusive_migration_entry(pfn);
  1963				else
  1964					entry = make_readable_migration_entry(pfn);
  1965				swp_pte = swp_entry_to_pte(entry);
  1966	
  1967				/*
  1968				 * pteval maps a zone device page and is therefore
  1969				 * a swap pte.
  1970				 */
  1971				if (pte_swp_soft_dirty(pteval))
  1972					swp_pte = pte_swp_mksoft_dirty(swp_pte);
  1973				if (pte_swp_uffd_wp(pteval))
  1974					swp_pte = pte_swp_mkuffd_wp(swp_pte);
  1975				set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
  1976				trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
  1977							compound_order(&folio->page));
  1978				/*
  1979				 * No need to invalidate here it will synchronize on
  1980				 * against the special swap migration pte.
  1981				 *
  1982				 * The assignment to subpage above was computed from a
  1983				 * swap PTE which results in an invalid pointer.
  1984				 * Since only PAGE_SIZE pages can currently be
  1985				 * migrated, just set it to page. This will need to be
  1986				 * changed when hugepage migrations to device private
  1987				 * memory are supported.
  1988				 */
  1989				subpage = &folio->page;
  1990			} else if (PageHWPoison(subpage)) {
  1991				pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
  1992				if (folio_test_hugetlb(folio)) {
  1993					hugetlb_count_sub(folio_nr_pages(folio), mm);
  1994					set_huge_swap_pte_at(mm, address,
  1995							     pvmw.pte, pteval,
  1996							     vma_mmu_pagesize(vma));
  1997				} else {
  1998					dec_mm_counter(mm, mm_counter(&folio->page));
  1999					set_pte_at(mm, address, pvmw.pte, pteval);
  2000				}
  2001	
  2002			} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
  2003				/*
  2004				 * The guest indicated that the page content is of no
  2005				 * interest anymore. Simply discard the pte, vmscan
  2006				 * will take care of the rest.
  2007				 * A future reference will then fault in a new zero
  2008				 * page. When userfaultfd is active, we must not drop
  2009				 * this page though, as its main user (postcopy
  2010				 * migration) will not expect userfaults on already
  2011				 * copied pages.
  2012				 */
  2013				dec_mm_counter(mm, mm_counter(&folio->page));
  2014				/* We have to invalidate as we cleared the pte */
  2015				mmu_notifier_invalidate_range(mm, address,
  2016							      address + PAGE_SIZE);
  2017			} else {
  2018				swp_entry_t entry;
  2019				pte_t swp_pte;
  2020	
  2021				if (arch_unmap_one(mm, vma, address, pteval) < 0) {
  2022					if (folio_test_hugetlb(folio))
> 2023						set_huge_pte_at(mm, address, pvmw.pte, pteval);
  2024					else
  2025						set_pte_at(mm, address, pvmw.pte, pteval);
  2026					ret = false;
  2027					page_vma_mapped_walk_done(&pvmw);
  2028					break;
  2029				}
  2030				VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
  2031					       !anon_exclusive, subpage);
  2032				if (anon_exclusive &&
  2033				    page_try_share_anon_rmap(subpage)) {
  2034					if (folio_test_hugetlb(folio))
  2035						set_huge_pte_at(mm, address, pvmw.pte, pteval);
  2036					else
  2037						set_pte_at(mm, address, pvmw.pte, pteval);
  2038					ret = false;
  2039					page_vma_mapped_walk_done(&pvmw);
  2040					break;
  2041				}
  2042	
  2043				/*
  2044				 * Store the pfn of the page in a special migration
  2045				 * pte. do_swap_page() will wait until the migration
  2046				 * pte is removed and then restart fault handling.
  2047				 */
  2048				if (pte_write(pteval))
  2049					entry = make_writable_migration_entry(
  2050								page_to_pfn(subpage));
  2051				else if (anon_exclusive)
  2052					entry = make_readable_exclusive_migration_entry(
  2053								page_to_pfn(subpage));
  2054				else
  2055					entry = make_readable_migration_entry(
  2056								page_to_pfn(subpage));
  2057	
  2058				swp_pte = swp_entry_to_pte(entry);
  2059				if (pte_soft_dirty(pteval))
  2060					swp_pte = pte_swp_mksoft_dirty(swp_pte);
  2061				if (pte_uffd_wp(pteval))
  2062					swp_pte = pte_swp_mkuffd_wp(swp_pte);
  2063				if (folio_test_hugetlb(folio))
  2064					set_huge_swap_pte_at(mm, address, pvmw.pte,
  2065							     swp_pte, vma_mmu_pagesize(vma));
  2066				else
  2067					set_pte_at(mm, address, pvmw.pte, swp_pte);
  2068				trace_set_migration_pte(address, pte_val(swp_pte),
  2069							compound_order(&folio->page));
  2070				/*
  2071				 * No need to invalidate here it will synchronize on
  2072				 * against the special swap migration pte.
  2073				 */
  2074			}
  2075	
  2076			/*
  2077			 * No need to call mmu_notifier_invalidate_range() it has be
  2078			 * done above for all cases requiring it to happen under page
  2079			 * table lock before mmu_notifier_invalidate_range_end()
  2080			 *
  2081			 * See Documentation/vm/mmu_notifier.rst
  2082			 */
  2083			page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
  2084			if (vma->vm_flags & VM_LOCKED)
  2085				mlock_page_drain_local();
  2086			folio_put(folio);
  2087		}
  2088	
  2089		mmu_notifier_invalidate_range_end(&range);
  2090	
  2091		return ret;
  2092	}
  2093
kernel test robot May 8, 2022, 12:11 p.m. UTC | #2
Hi Baolin,

I love your patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on next-20220506]
[cannot apply to hnaz-mm/master arm64/for-next/core linus/master v5.18-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Baolin-Wang/Fix-CONT-PTE-PMD-size-hugetlb-issue-when-unmapping-or-migrating/20220508-174036
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: x86_64-randconfig-a014 (https://download.01.org/0day-ci/archive/20220508/202205081950.IpKFNYip-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project a385645b470e2d3a1534aae618ea56b31177639f)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/907981b27213707fdb2f8a24c107d6752a09a773
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Baolin-Wang/Fix-CONT-PTE-PMD-size-hugetlb-issue-when-unmapping-or-migrating/20220508-174036
        git checkout 907981b27213707fdb2f8a24c107d6752a09a773
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> mm/rmap.c:1931:13: error: call to undeclared function 'huge_ptep_clear_flush'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
                           pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
                                    ^
   mm/rmap.c:1931:13: note: did you mean 'ptep_clear_flush'?
   include/linux/pgtable.h:431:14: note: 'ptep_clear_flush' declared here
   extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
                ^
>> mm/rmap.c:1931:11: error: assigning to 'pte_t' from incompatible type 'int'
                           pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
                                  ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> mm/rmap.c:2023:6: error: call to undeclared function 'set_huge_pte_at'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
                                           set_huge_pte_at(mm, address, pvmw.pte, pteval);
                                           ^
   mm/rmap.c:2035:6: error: call to undeclared function 'set_huge_pte_at'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
                                           set_huge_pte_at(mm, address, pvmw.pte, pteval);
                                           ^
   4 errors generated.


vim +/huge_ptep_clear_flush +1931 mm/rmap.c

  1883	
  1884			/* Unexpected PMD-mapped THP? */
  1885			VM_BUG_ON_FOLIO(!pvmw.pte, folio);
  1886	
  1887			subpage = folio_page(folio,
  1888					pte_pfn(*pvmw.pte) - folio_pfn(folio));
  1889			address = pvmw.address;
  1890			anon_exclusive = folio_test_anon(folio) &&
  1891					 PageAnonExclusive(subpage);
  1892	
  1893			if (folio_test_hugetlb(folio)) {
  1894				/*
  1895				 * huge_pmd_unshare may unmap an entire PMD page.
  1896				 * There is no way of knowing exactly which PMDs may
  1897				 * be cached for this mm, so we must flush them all.
  1898				 * start/end were already adjusted above to cover this
  1899				 * range.
  1900				 */
  1901				flush_cache_range(vma, range.start, range.end);
  1902	
  1903				if (!folio_test_anon(folio)) {
  1904					/*
  1905					 * To call huge_pmd_unshare, i_mmap_rwsem must be
  1906					 * held in write mode.  Caller needs to explicitly
  1907					 * do this outside rmap routines.
  1908					 */
  1909					VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
  1910	
  1911					if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
  1912						flush_tlb_range(vma, range.start, range.end);
  1913						mmu_notifier_invalidate_range(mm, range.start,
  1914									      range.end);
  1915	
  1916						/*
  1917						 * The ref count of the PMD page was dropped
  1918						 * which is part of the way map counting
  1919						 * is done for shared PMDs.  Return 'true'
  1920						 * here.  When there is no other sharing,
  1921						 * huge_pmd_unshare returns false and we will
  1922						 * unmap the actual page and drop map count
  1923						 * to zero.
  1924						 */
  1925						page_vma_mapped_walk_done(&pvmw);
  1926						break;
  1927					}
  1928				}
  1929	
  1930				/* Nuke the hugetlb page table entry */
> 1931				pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
  1932			} else {
  1933				flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
  1934				/* Nuke the page table entry. */
  1935				pteval = ptep_clear_flush(vma, address, pvmw.pte);
  1936			}
  1937	
  1938			/* Set the dirty flag on the folio now the pte is gone. */
  1939			if (pte_dirty(pteval))
  1940				folio_mark_dirty(folio);
  1941	
  1942			/* Update high watermark before we lower rss */
  1943			update_hiwater_rss(mm);
  1944	
  1945			if (folio_is_zone_device(folio)) {
  1946				unsigned long pfn = folio_pfn(folio);
  1947				swp_entry_t entry;
  1948				pte_t swp_pte;
  1949	
  1950				if (anon_exclusive)
  1951					BUG_ON(page_try_share_anon_rmap(subpage));
  1952	
  1953				/*
  1954				 * Store the pfn of the page in a special migration
  1955				 * pte. do_swap_page() will wait until the migration
  1956				 * pte is removed and then restart fault handling.
  1957				 */
  1958				entry = pte_to_swp_entry(pteval);
  1959				if (is_writable_device_private_entry(entry))
  1960					entry = make_writable_migration_entry(pfn);
  1961				else if (anon_exclusive)
  1962					entry = make_readable_exclusive_migration_entry(pfn);
  1963				else
  1964					entry = make_readable_migration_entry(pfn);
  1965				swp_pte = swp_entry_to_pte(entry);
  1966	
  1967				/*
  1968				 * pteval maps a zone device page and is therefore
  1969				 * a swap pte.
  1970				 */
  1971				if (pte_swp_soft_dirty(pteval))
  1972					swp_pte = pte_swp_mksoft_dirty(swp_pte);
  1973				if (pte_swp_uffd_wp(pteval))
  1974					swp_pte = pte_swp_mkuffd_wp(swp_pte);
  1975				set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
  1976				trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
  1977							compound_order(&folio->page));
  1978				/*
  1979				 * No need to invalidate here it will synchronize on
  1980				 * against the special swap migration pte.
  1981				 *
  1982				 * The assignment to subpage above was computed from a
  1983				 * swap PTE which results in an invalid pointer.
  1984				 * Since only PAGE_SIZE pages can currently be
  1985				 * migrated, just set it to page. This will need to be
  1986				 * changed when hugepage migrations to device private
  1987				 * memory are supported.
  1988				 */
  1989				subpage = &folio->page;
  1990			} else if (PageHWPoison(subpage)) {
  1991				pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
  1992				if (folio_test_hugetlb(folio)) {
  1993					hugetlb_count_sub(folio_nr_pages(folio), mm);
  1994					set_huge_swap_pte_at(mm, address,
  1995							     pvmw.pte, pteval,
  1996							     vma_mmu_pagesize(vma));
  1997				} else {
  1998					dec_mm_counter(mm, mm_counter(&folio->page));
  1999					set_pte_at(mm, address, pvmw.pte, pteval);
  2000				}
  2001	
  2002			} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
  2003				/*
  2004				 * The guest indicated that the page content is of no
  2005				 * interest anymore. Simply discard the pte, vmscan
  2006				 * will take care of the rest.
  2007				 * A future reference will then fault in a new zero
  2008				 * page. When userfaultfd is active, we must not drop
  2009				 * this page though, as its main user (postcopy
  2010				 * migration) will not expect userfaults on already
  2011				 * copied pages.
  2012				 */
  2013				dec_mm_counter(mm, mm_counter(&folio->page));
  2014				/* We have to invalidate as we cleared the pte */
  2015				mmu_notifier_invalidate_range(mm, address,
  2016							      address + PAGE_SIZE);
  2017			} else {
  2018				swp_entry_t entry;
  2019				pte_t swp_pte;
  2020	
  2021				if (arch_unmap_one(mm, vma, address, pteval) < 0) {
  2022					if (folio_test_hugetlb(folio))
> 2023						set_huge_pte_at(mm, address, pvmw.pte, pteval);
  2024					else
  2025						set_pte_at(mm, address, pvmw.pte, pteval);
  2026					ret = false;
  2027					page_vma_mapped_walk_done(&pvmw);
  2028					break;
  2029				}
  2030				VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
  2031					       !anon_exclusive, subpage);
  2032				if (anon_exclusive &&
  2033				    page_try_share_anon_rmap(subpage)) {
  2034					if (folio_test_hugetlb(folio))
  2035						set_huge_pte_at(mm, address, pvmw.pte, pteval);
  2036					else
  2037						set_pte_at(mm, address, pvmw.pte, pteval);
  2038					ret = false;
  2039					page_vma_mapped_walk_done(&pvmw);
  2040					break;
  2041				}
  2042	
  2043				/*
  2044				 * Store the pfn of the page in a special migration
  2045				 * pte. do_swap_page() will wait until the migration
  2046				 * pte is removed and then restart fault handling.
  2047				 */
  2048				if (pte_write(pteval))
  2049					entry = make_writable_migration_entry(
  2050								page_to_pfn(subpage));
  2051				else if (anon_exclusive)
  2052					entry = make_readable_exclusive_migration_entry(
  2053								page_to_pfn(subpage));
  2054				else
  2055					entry = make_readable_migration_entry(
  2056								page_to_pfn(subpage));
  2057	
  2058				swp_pte = swp_entry_to_pte(entry);
  2059				if (pte_soft_dirty(pteval))
  2060					swp_pte = pte_swp_mksoft_dirty(swp_pte);
  2061				if (pte_uffd_wp(pteval))
  2062					swp_pte = pte_swp_mkuffd_wp(swp_pte);
  2063				if (folio_test_hugetlb(folio))
  2064					set_huge_swap_pte_at(mm, address, pvmw.pte,
  2065							     swp_pte, vma_mmu_pagesize(vma));
  2066				else
  2067					set_pte_at(mm, address, pvmw.pte, swp_pte);
  2068				trace_set_migration_pte(address, pte_val(swp_pte),
  2069							compound_order(&folio->page));
  2070				/*
  2071				 * No need to invalidate here it will synchronize on
  2072				 * against the special swap migration pte.
  2073				 */
  2074			}
  2075	
  2076			/*
  2077			 * No need to call mmu_notifier_invalidate_range() it has be
  2078			 * done above for all cases requiring it to happen under page
  2079			 * table lock before mmu_notifier_invalidate_range_end()
  2080			 *
  2081			 * See Documentation/vm/mmu_notifier.rst
  2082			 */
  2083			page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
  2084			if (vma->vm_flags & VM_LOCKED)
  2085				mlock_page_drain_local();
  2086			folio_put(folio);
  2087		}
  2088	
  2089		mmu_notifier_invalidate_range_end(&range);
  2090	
  2091		return ret;
  2092	}
  2093
Baolin Wang May 8, 2022, 1:13 p.m. UTC | #3
Hi,

On 5/8/2022 8:01 PM, kernel test robot wrote:
> Hi Baolin,
> 
> I love your patch! Yet something to improve:
> 
> [auto build test ERROR on akpm-mm/mm-everything]
> [also build test ERROR on next-20220506]
> [cannot apply to hnaz-mm/master arm64/for-next/core linus/master v5.18-rc5]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Baolin-Wang/Fix-CONT-PTE-PMD-size-hugetlb-issue-when-unmapping-or-migrating/20220508-174036
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> config: x86_64-randconfig-a013 (https://download.01.org/0day-ci/archive/20220508/202205081910.mStoC5rj-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
> reproduce (this is a W=1 build):
>          # https://github.com/intel-lab-lkp/linux/commit/907981b27213707fdb2f8a24c107d6752a09a773
>          git remote add linux-review https://github.com/intel-lab-lkp/linux
>          git fetch --no-tags linux-review Baolin-Wang/Fix-CONT-PTE-PMD-size-hugetlb-issue-when-unmapping-or-migrating/20220508-174036
>          git checkout 907981b27213707fdb2f8a24c107d6752a09a773
>          # save the config file
>          mkdir build_dir && cp config build_dir/.config
>          make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>     mm/rmap.c: In function 'try_to_migrate_one':
>>> mm/rmap.c:1931:34: error: implicit declaration of function 'huge_ptep_clear_flush'; did you mean 'ptep_clear_flush'? [-Werror=implicit-function-declaration]
>      1931 |                         pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
>           |                                  ^~~~~~~~~~~~~~~~~~~~~
>           |                                  ptep_clear_flush
>>> mm/rmap.c:1931:34: error: incompatible types when assigning to type 'pte_t' from type 'int'
>>> mm/rmap.c:2023:41: error: implicit declaration of function 'set_huge_pte_at'; did you mean 'set_huge_swap_pte_at'? [-Werror=implicit-function-declaration]
>      2023 |                                         set_huge_pte_at(mm, address, pvmw.pte, pteval);
>           |                                         ^~~~~~~~~~~~~~~
>           |                                         set_huge_swap_pte_at
>     cc1: some warnings being treated as errors

Thanks for reporting. I think I should add some dummy functions in 
hugetlb.h file if the CONFIG_HUGETLB_PAGE is not selected. I can pass 
the building with below changes and your config file.

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 306d6ef..9f71043 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1093,6 +1093,17 @@ static inline void set_huge_swap_pte_at(struct 
mm_struct *mm, unsigned long addr
                                         pte_t *ptep, pte_t pte, 
unsigned long sz)
  {
  }
+
+static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
+                                         unsigned long addr, pte_t *ptep)
+{
+       return ptep_get(ptep);
+}
+
+static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long 
addr,
+                                  pte_t *ptep, pte_t pte)
+{
+}
  #endif /* CONFIG_HUGETLB_PAGE */
Muchun Song May 8, 2022, 1:31 p.m. UTC | #4
On Sun, May 08, 2022 at 05:36:40PM +0800, Baolin Wang wrote:
> On some architectures (like ARM64), it can support CONT-PTE/PMD size
> hugetlb, which means it can support not only PMD/PUD size hugetlb:
> 2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page
> size specified.
> 
> When migrating a hugetlb page, we will get the relevant page table
> entry by huge_pte_offset() only once to nuke it and remap it with
> a migration pte entry. This is correct for PMD or PUD size hugetlb,
> since they always contain only one pmd entry or pud entry in the
> page table.
> 
> However this is incorrect for CONT-PTE and CONT-PMD size hugetlb,
> since they can contain several continuous pte or pmd entry with
> same page table attributes. So we will nuke or remap only one pte
> or pmd entry for this CONT-PTE/PMD size hugetlb page, which is
> not expected for hugetlb migration. The problem is we can still
> continue to modify the subpages' data of a hugetlb page during
> migrating a hugetlb page, which can cause a serious data consistent
> issue, since we did not nuke the page table entry and set a
> migration pte for the subpages of a hugetlb page.
> 
> To fix this issue, we should change to use huge_ptep_clear_flush()
> to nuke a hugetlb page table, and remap it with set_huge_pte_at()
> and set_huge_swap_pte_at() when migrating a hugetlb page, which
> already considered the CONT-PTE or CONT-PMD size hugetlb.
> 
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>

This looks fine to me.

Reviewed-by: Muchun Song <songmuchun@bytedance.com>

Thanks.
Mike Kravetz May 9, 2022, 9:05 p.m. UTC | #5
On 5/8/22 02:36, Baolin Wang wrote:
> On some architectures (like ARM64), it can support CONT-PTE/PMD size
> hugetlb, which means it can support not only PMD/PUD size hugetlb:
> 2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page
> size specified.
> 
> When migrating a hugetlb page, we will get the relevant page table
> entry by huge_pte_offset() only once to nuke it and remap it with
> a migration pte entry. This is correct for PMD or PUD size hugetlb,
> since they always contain only one pmd entry or pud entry in the
> page table.
> 
> However this is incorrect for CONT-PTE and CONT-PMD size hugetlb,
> since they can contain several continuous pte or pmd entry with
> same page table attributes. So we will nuke or remap only one pte
> or pmd entry for this CONT-PTE/PMD size hugetlb page, which is
> not expected for hugetlb migration. The problem is we can still
> continue to modify the subpages' data of a hugetlb page during
> migrating a hugetlb page, which can cause a serious data consistent
> issue, since we did not nuke the page table entry and set a
> migration pte for the subpages of a hugetlb page.
> 
> To fix this issue, we should change to use huge_ptep_clear_flush()
> to nuke a hugetlb page table, and remap it with set_huge_pte_at()
> and set_huge_swap_pte_at() when migrating a hugetlb page, which
> already considered the CONT-PTE or CONT-PMD size hugetlb.
> 
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>  mm/rmap.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)

With the addition of !CONFIG_HUGETLB_PAGE stubs,

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
diff mbox series

Patch

diff --git a/mm/rmap.c b/mm/rmap.c
index 6fdd198..7cf2408 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1924,13 +1924,15 @@  static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 					break;
 				}
 			}
+
+			/* Nuke the hugetlb page table entry */
+			pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
 		} else {
 			flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
+			/* Nuke the page table entry. */
+			pteval = ptep_clear_flush(vma, address, pvmw.pte);
 		}
 
-		/* Nuke the page table entry. */
-		pteval = ptep_clear_flush(vma, address, pvmw.pte);
-
 		/* Set the dirty flag on the folio now the pte is gone. */
 		if (pte_dirty(pteval))
 			folio_mark_dirty(folio);
@@ -2015,7 +2017,10 @@  static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 			pte_t swp_pte;
 
 			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
-				set_pte_at(mm, address, pvmw.pte, pteval);
+				if (folio_test_hugetlb(folio))
+					set_huge_pte_at(mm, address, pvmw.pte, pteval);
+				else
+					set_pte_at(mm, address, pvmw.pte, pteval);
 				ret = false;
 				page_vma_mapped_walk_done(&pvmw);
 				break;
@@ -2024,7 +2029,10 @@  static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 				       !anon_exclusive, subpage);
 			if (anon_exclusive &&
 			    page_try_share_anon_rmap(subpage)) {
-				set_pte_at(mm, address, pvmw.pte, pteval);
+				if (folio_test_hugetlb(folio))
+					set_huge_pte_at(mm, address, pvmw.pte, pteval);
+				else
+					set_pte_at(mm, address, pvmw.pte, pteval);
 				ret = false;
 				page_vma_mapped_walk_done(&pvmw);
 				break;
@@ -2050,7 +2058,11 @@  static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 				swp_pte = pte_swp_mksoft_dirty(swp_pte);
 			if (pte_uffd_wp(pteval))
 				swp_pte = pte_swp_mkuffd_wp(swp_pte);
-			set_pte_at(mm, address, pvmw.pte, swp_pte);
+			if (folio_test_hugetlb(folio))
+				set_huge_swap_pte_at(mm, address, pvmw.pte,
+						     swp_pte, vma_mmu_pagesize(vma));
+			else
+				set_pte_at(mm, address, pvmw.pte, swp_pte);
 			trace_set_migration_pte(address, pte_val(swp_pte),
 						compound_order(&folio->page));
 			/*