mm: thp: check pmd migration entry in common path
When THP migration is being used, memory management code needs to handle
pmd migration entries properly. This patch uses !pmd_present() or
is_swap_pmd() (depending on whether pmd_none() needs separate code or
not) to check pmd migration entries at the places where a pmd entry is
present.
Since pmd-related code uses split_huge_page(), split_huge_pmd(),
pmd_trans_huge(), pmd_trans_unstable(), or
pmd_none_or_trans_huge_or_clear_bad(), this patch:
1. adds pmd migration entry split code in split_huge_pmd(),
2. takes care of pmd migration entries whenever pmd_trans_huge() is present,
3. makes pmd_none_or_trans_huge_or_clear_bad() pmd migration entry aware.
Since split_huge_page() uses split_huge_pmd() and pmd_trans_unstable()
is equivalent to pmd_none_or_trans_huge_or_clear_bad(), we do not change
them.
Until this commit, a pmd entry should be:
1. pointing to a pte page,
2. is_swap_pmd(),
3. pmd_trans_huge(),
4. pmd_devmap(), or
5. pmd_none().
Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 937f007..b82585e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -928,6 +928,23 @@
ret = -EAGAIN;
pmd = *src_pmd;
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ if (unlikely(is_swap_pmd(pmd))) {
+ swp_entry_t entry = pmd_to_swp_entry(pmd);
+
+ VM_BUG_ON(!is_pmd_migration_entry(pmd));
+ if (is_write_migration_entry(entry)) {
+ make_migration_entry_read(&entry);
+ pmd = swp_entry_to_pmd(entry);
+ set_pmd_at(src_mm, addr, src_pmd, pmd);
+ }
+ set_pmd_at(dst_mm, addr, dst_pmd, pmd);
+ ret = 0;
+ goto out_unlock;
+ }
+#endif
+
if (unlikely(!pmd_trans_huge(pmd))) {
pte_free(dst_mm, pgtable);
goto out_unlock;
@@ -1599,6 +1616,12 @@
if (is_huge_zero_pmd(orig_pmd))
goto out;
+ if (unlikely(!pmd_present(orig_pmd))) {
+ VM_BUG_ON(thp_migration_supported() &&
+ !is_pmd_migration_entry(orig_pmd));
+ goto out;
+ }
+
page = pmd_page(orig_pmd);
/*
* If other processes are mapping this page, we couldn't discard
@@ -1810,6 +1833,25 @@
preserve_write = prot_numa && pmd_write(*pmd);
ret = 1;
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ if (is_swap_pmd(*pmd)) {
+ swp_entry_t entry = pmd_to_swp_entry(*pmd);
+
+ VM_BUG_ON(!is_pmd_migration_entry(*pmd));
+ if (is_write_migration_entry(entry)) {
+ pmd_t newpmd;
+ /*
+ * A protection check is difficult so
+ * just be safe and disable write
+ */
+ make_migration_entry_read(&entry);
+ newpmd = swp_entry_to_pmd(entry);
+ set_pmd_at(mm, addr, pmd, newpmd);
+ }
+ goto unlock;
+ }
+#endif
+
/*
* Avoid trapping faults against the zero page. The read-only
* data is likely to be read-cached on the local CPU and
@@ -1875,7 +1917,8 @@
{
spinlock_t *ptl;
ptl = pmd_lock(vma->vm_mm, pmd);
- if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
+ if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
+ pmd_devmap(*pmd)))
return ptl;
spin_unlock(ptl);
return NULL;
@@ -1993,14 +2036,15 @@
struct page *page;
pgtable_t pgtable;
pmd_t _pmd;
- bool young, write, dirty, soft_dirty;
+ bool young, write, dirty, soft_dirty, pmd_migration = false;
unsigned long addr;
int i;
VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
- VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
+ VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
+ && !pmd_devmap(*pmd));
count_vm_event(THP_SPLIT_PMD);
@@ -2025,7 +2069,16 @@
return __split_huge_zero_page_pmd(vma, haddr, pmd);
}
- page = pmd_page(*pmd);
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ pmd_migration = is_pmd_migration_entry(*pmd);
+ if (pmd_migration) {
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(*pmd);
+ page = pfn_to_page(swp_offset(entry));
+ } else
+#endif
+ page = pmd_page(*pmd);
VM_BUG_ON_PAGE(!page_count(page), page);
page_ref_add(page, HPAGE_PMD_NR - 1);
write = pmd_write(*pmd);
@@ -2044,7 +2097,7 @@
* transferred to avoid any possibility of altering
* permissions across VMAs.
*/
- if (freeze) {
+ if (freeze || pmd_migration) {
swp_entry_t swp_entry;
swp_entry = make_migration_entry(page + i, write);
entry = swp_entry_to_pte(swp_entry);
@@ -2143,7 +2196,7 @@
page = pmd_page(*pmd);
if (PageMlocked(page))
clear_page_mlock(page);
- } else if (!pmd_devmap(*pmd))
+ } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
goto out;
__split_huge_pmd_locked(vma, pmd, haddr, freeze);
out: