Support transparent huge page migration to ZONE_DEVICE private memory.
A new flag (MIGRATE_PFN_COMPOUND) is added to the input PFN array to
indicate the huge page was fully mapped by the CPU.
Export prep_compound_page() so that device drivers can create huge
device private pages after calling memremap_pages().
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
---
include/linux/migrate.h | 1 +
include/linux/mm.h | 1 +
mm/huge_memory.c | 30 ++++--
mm/internal.h | 1 -
mm/memory.c | 10 +-
mm/memremap.c | 9 +-
mm/migrate.c | 226 ++++++++++++++++++++++++++++++++--------
mm/page_alloc.c | 1 +
8 files changed, 226 insertions(+), 53 deletions(-)
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 3e546cbf03dd..f6a64965c8bd 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -166,6 +166,7 @@ static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm,
#define MIGRATE_PFN_MIGRATE (1UL << 1)
#define MIGRATE_PFN_LOCKED (1UL << 2)
#define MIGRATE_PFN_WRITE (1UL << 3)
+#define MIGRATE_PFN_COMPOUND (1UL << 4)
#define MIGRATE_PFN_SHIFT 6
static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index dc7b87310c10..020b9dd3cddb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -932,6 +932,7 @@ static inline unsigned int page_shift(struct page *page)
}
void free_compound_page(struct page *page);
+void prep_compound_page(struct page *page, unsigned int order);
#ifdef CONFIG_MMU
/*
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 78c84bee7e29..25d95f7b1e98 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1663,23 +1663,35 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
} else {
struct page *page = NULL;
int flush_needed = 1;
+ bool is_anon = false;
if (pmd_present(orig_pmd)) {
page = pmd_page(orig_pmd);
+ is_anon = PageAnon(page);
page_remove_rmap(page, true);
VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
VM_BUG_ON_PAGE(!PageHead(page), page);
} else if (thp_migration_supported()) {
swp_entry_t entry;
- VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
entry = pmd_to_swp_entry(orig_pmd);
- page = pfn_to_page(swp_offset(entry));
+ if (is_device_private_entry(entry)) {
+ page = device_private_entry_to_page(entry);
+ is_anon = PageAnon(page);
+ page_remove_rmap(page, true);
+ VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+ put_page(page);
+ } else {
+ VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
+ page = pfn_to_page(swp_offset(entry));
+ is_anon = PageAnon(page);
+ }
flush_needed = 0;
} else
WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
- if (PageAnon(page)) {
+ if (is_anon) {
zap_deposited_table(tlb->mm, pmd);
add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
} else {
@@ -1778,8 +1790,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
/*
* Returns
* - 0 if PMD could not be locked
- * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
- * - HPAGE_PMD_NR is protections changed and TLB flush necessary
+ * - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
+ * - HPAGE_PMD_NR if protections changed and TLB flush necessary
*/
int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, pgprot_t newprot, unsigned long cp_flags)
@@ -2689,7 +2701,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
if (!list_empty(page_deferred_list(head))) {
ds_queue->split_queue_len--;
- list_del(page_deferred_list(head));
+ list_del_init(page_deferred_list(head));
}
spin_unlock(&ds_queue->split_queue_lock);
if (mapping) {
@@ -2743,7 +2755,7 @@ void free_transhuge_page(struct page *page)
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (!list_empty(page_deferred_list(page))) {
ds_queue->split_queue_len--;
- list_del(page_deferred_list(page));
+ list_del_init(page_deferred_list(page));
}
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
free_compound_page(page);
@@ -2963,6 +2975,10 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
pmde = pmd_mksoft_dirty(pmde);
if (is_write_migration_entry(entry))
pmde = maybe_pmd_mkwrite(pmde, vma);
+ if (unlikely(is_device_private_page(new))) {
+ entry = make_device_private_entry(new, pmd_write(pmde));
+ pmde = swp_entry_to_pmd(entry);
+ }
flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
if (PageAnon(new))
diff --git a/mm/internal.h b/mm/internal.h
index 9886db20d94f..58f051a14dae 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -196,7 +196,6 @@ extern void __putback_isolated_page(struct page *page, unsigned int order,
extern void memblock_free_pages(struct page *page, unsigned long pfn,
unsigned int order);
extern void __free_pages_core(struct page *page, unsigned int order);
-extern void prep_compound_page(struct page *page, unsigned int order);
extern void post_alloc_hook(struct page *page, unsigned int order,
gfp_t gfp_flags);
extern int user_min_free_kbytes;
diff --git a/mm/memory.c b/mm/memory.c
index dc7f3543b1fd..4e03d1a2ead5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4322,9 +4322,15 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
barrier();
if (unlikely(is_swap_pmd(orig_pmd))) {
+ swp_entry_t entry = pmd_to_swp_entry(orig_pmd);
+
+ if (is_device_private_entry(entry)) {
+ vmf.page = device_private_entry_to_page(entry);
+ return vmf.page->pgmap->ops->migrate_to_ram(&vmf);
+ }
VM_BUG_ON(thp_migration_supported() &&
- !is_pmd_migration_entry(orig_pmd));
- if (is_pmd_migration_entry(orig_pmd))
+ !is_migration_entry(entry));
+ if (is_migration_entry(entry))
pmd_migration_entry_wait(mm, vmf.pmd);
return 0;
}
diff --git a/mm/memremap.c b/mm/memremap.c
index 03e38b7a38f1..4231054188b4 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -132,8 +132,13 @@ void memunmap_pages(struct dev_pagemap *pgmap)
int nid;
dev_pagemap_kill(pgmap);
- for_each_device_pfn(pfn, pgmap)
- put_page(pfn_to_page(pfn));
+ for_each_device_pfn(pfn, pgmap) {
+ struct page *page = pfn_to_page(pfn);
+ unsigned int order = compound_order(page);
+
+ put_page(page);
+ pfn += (1U << order) - 1;
+ }
dev_pagemap_cleanup(pgmap);
/* make sure to access a memmap that was actually initialized */
diff --git a/mm/migrate.c b/mm/migrate.c
index 87c52e0ee580..1536677cefc9 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -51,6 +51,7 @@
#include <linux/oom.h>
#include <asm/tlbflush.h>
+#include <asm/pgalloc.h>
#define CREATE_TRACE_POINTS
#include <trace/events/migrate.h>
@@ -2185,6 +2186,8 @@ static int migrate_vma_collect_hole(unsigned long start,
for (addr = start; addr < end; addr += PAGE_SIZE) {
migrate->src[migrate->npages] = flags;
+ if ((addr & ~PMD_MASK) == 0 && (end & ~PMD_MASK) == 0)
+ migrate->src[migrate->npages] |= MIGRATE_PFN_COMPOUND;
migrate->dst[migrate->npages] = 0;
migrate->npages++;
migrate->cpages++;
@@ -2219,48 +2222,87 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
unsigned long addr = start, unmapped = 0;
spinlock_t *ptl;
pte_t *ptep;
+ pmd_t pmd;
again:
- if (pmd_none(*pmdp))
+ pmd = READ_ONCE(*pmdp);
+ if (pmd_none(pmd))
return migrate_vma_collect_hole(start, end, -1, walk);
- if (pmd_trans_huge(*pmdp)) {
+ if (pmd_trans_huge(pmd) || !pmd_present(pmd)) {
struct page *page;
+ unsigned long write = 0;
+ int ret;
ptl = pmd_lock(mm, pmdp);
- if (unlikely(!pmd_trans_huge(*pmdp))) {
- spin_unlock(ptl);
- goto again;
- }
+ if (pmd_trans_huge(*pmdp)) {
+ page = pmd_page(*pmdp);
+ if (is_huge_zero_page(page)) {
+ spin_unlock(ptl);
+ return migrate_vma_collect_hole(start, end, -1,
+ walk);
+ }
+ if (pmd_write(*pmdp))
+ write = MIGRATE_PFN_WRITE;
+ } else if (!pmd_present(*pmdp)) {
+ swp_entry_t entry = pmd_to_swp_entry(*pmdp);
- page = pmd_page(*pmdp);
- if (is_huge_zero_page(page)) {
- spin_unlock(ptl);
- split_huge_pmd(vma, pmdp, addr);
- if (pmd_trans_unstable(pmdp))
+ if (!is_device_private_entry(entry)) {
+ spin_unlock(ptl);
return migrate_vma_collect_skip(start, end,
walk);
+ }
+ page = device_private_entry_to_page(entry);
+ if (is_write_device_private_entry(entry))
+ write = MIGRATE_PFN_WRITE;
} else {
- int ret;
+ spin_unlock(ptl);
+ goto again;
+ }
- get_page(page);
+ get_page(page);
+ if (unlikely(!trylock_page(page))) {
spin_unlock(ptl);
- if (unlikely(!trylock_page(page)))
- return migrate_vma_collect_skip(start, end,
- walk);
- ret = split_huge_page(page);
- unlock_page(page);
put_page(page);
- if (ret)
- return migrate_vma_collect_skip(start, end,
- walk);
- if (pmd_none(*pmdp))
- return migrate_vma_collect_hole(start, end, -1,
- walk);
+ return migrate_vma_collect_skip(start, end, walk);
+ }
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ if ((start & HPAGE_PMD_MASK) == start &&
+ start + HPAGE_PMD_SIZE == end) {
+ struct page_vma_mapped_walk vmw = {
+ .vma = vma,
+ .address = start,
+ .pmd = pmdp,
+ .ptl = ptl,
+ };
+
+ migrate->src[migrate->npages] = write |
+ migrate_pfn(page_to_pfn(page)) |
+ MIGRATE_PFN_MIGRATE | MIGRATE_PFN_LOCKED |
+ MIGRATE_PFN_COMPOUND;
+ migrate->dst[migrate->npages] = 0;
+ migrate->npages++;
+ migrate->cpages++;
+ migrate_vma_collect_skip(start + PAGE_SIZE, end, walk);
+
+ /* Note that this also removes the page from the rmap. */
+ set_pmd_migration_entry(&vmw, page);
+ spin_unlock(ptl);
+
+ return 0;
}
+#endif
+ spin_unlock(ptl);
+ ret = split_huge_page(page);
+ unlock_page(page);
+ put_page(page);
+ if (ret)
+ return migrate_vma_collect_skip(start, end, walk);
+ if (pmd_none(*pmdp))
+ return migrate_vma_collect_hole(start, end, -1, walk);
}
- if (unlikely(pmd_bad(*pmdp)))
+ if (unlikely(pmd_bad(pmd) || pmd_devmap(pmd)))
return migrate_vma_collect_skip(start, end, walk);
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
@@ -2310,8 +2352,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
}
- /* FIXME support THP */
- if (!page || !page->mapping || PageTransCompound(page)) {
+ if (!page || !page->mapping) {
mpfn = 0;
goto next;
}
@@ -2420,14 +2461,6 @@ static bool migrate_vma_check_page(struct page *page)
*/
int extra = 1;
- /*
- * FIXME support THP (transparent huge page), it is bit more complex to
- * check them than regular pages, because they can be mapped with a pmd
- * or with a pte (split pte mapping).
- */
- if (PageCompound(page))
- return false;
-
/* Page from ZONE_DEVICE have one extra reference */
if (is_zone_device_page(page)) {
/*
@@ -2726,13 +2759,115 @@ int migrate_vma_setup(struct migrate_vma *args)
}
EXPORT_SYMBOL(migrate_vma_setup);
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+/*
+ * This code closely follows:
+ * do_huge_pmd_anonymous_page()
+ * __do_huge_pmd_anonymous_page()
+ * except that the page being inserted is likely to be a device private page
+ * instead of an allocated or zero page.
+ */
+static int insert_huge_pmd_anonymous_page(struct vm_area_struct *vma,
+ unsigned long haddr,
+ struct page *page,
+ unsigned long *src,
+ unsigned long *dst,
+ pmd_t *pmdp)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned int i;
+ spinlock_t *ptl;
+ bool flush = false;
+ pgtable_t pgtable;
+ gfp_t gfp;
+ pmd_t entry;
+
+ if (WARN_ON_ONCE(compound_order(page) != HPAGE_PMD_ORDER))
+ goto abort;
+
+ if (unlikely(anon_vma_prepare(vma)))
+ goto abort;
+
+ prep_transhuge_page(page);
+
+ gfp = GFP_TRANSHUGE_LIGHT;
+ if (mem_cgroup_charge(page, mm, gfp))
+ goto abort;
+
+ pgtable = pte_alloc_one(mm);
+ if (unlikely(!pgtable))
+ goto abort;
+
+ __SetPageUptodate(page);
+
+ if (is_zone_device_page(page)) {
+ if (!is_device_private_page(page))
+ goto pgtable_abort;
+ entry = swp_entry_to_pmd(make_device_private_entry(page,
+ vma->vm_flags & VM_WRITE));
+ } else {
+ entry = mk_huge_pmd(page, vma->vm_page_prot);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ }
+
+ ptl = pmd_lock(mm, pmdp);
+
+ if (check_stable_address_space(mm))
+ goto unlock_abort;
+
+ /*
+ * Check for userfaultfd but do not deliver the fault. Instead,
+ * just back off.
+ */
+ if (userfaultfd_missing(vma))
+ goto unlock_abort;
+
+ if (pmd_present(*pmdp)) {
+ if (!is_huge_zero_pmd(*pmdp))
+ goto unlock_abort;
+ flush = true;
+ } else if (!pmd_none(*pmdp))
+ goto unlock_abort;
+
+ get_page(page);
+ page_add_new_anon_rmap(page, vma, haddr, true);
+ if (!is_device_private_page(page))
+ lru_cache_add_active_or_unevictable(page, vma);
+ if (flush) {
+ pte_free(mm, pgtable);
+ flush_cache_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
+ pmdp_invalidate(vma, haddr, pmdp);
+ } else {
+ pgtable_trans_huge_deposit(mm, pmdp, pgtable);
+ mm_inc_nr_ptes(mm);
+ }
+ set_pmd_at(mm, haddr, pmdp, entry);
+ update_mmu_cache_pmd(vma, haddr, pmdp);
+ add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ spin_unlock(ptl);
+ count_vm_event(THP_FAULT_ALLOC);
+ count_memcg_event_mm(mm, THP_FAULT_ALLOC);
+
+ return 0;
+
+unlock_abort:
+ spin_unlock(ptl);
+pgtable_abort:
+ pte_free(mm, pgtable);
+abort:
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ src[i] &= ~MIGRATE_PFN_MIGRATE;
+ return -EINVAL;
+}
+#endif
+
/*
* This code closely matches the code in:
* __handle_mm_fault()
* handle_pte_fault()
* do_anonymous_page()
- * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
- * private page.
+ * to map in an anonymous zero page except the struct page is already allocated
+ * and will likely be a ZONE_DEVICE private page.
*/
static void migrate_vma_insert_page(struct migrate_vma *migrate,
unsigned long addr,
@@ -2766,7 +2901,16 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
if (!pmdp)
goto abort;
- if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ if (*dst & MIGRATE_PFN_COMPOUND) {
+ int ret = insert_huge_pmd_anonymous_page(vma, addr, page, src,
+ dst, pmdp);
+ if (ret)
+ goto abort;
+ return;
+ }
+#endif
+ if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp) || pmd_bad(*pmdp))
goto abort;
/*
@@ -2804,7 +2948,8 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
entry = swp_entry_to_pte(swp_entry);
- }
+ } else
+ goto abort;
} else {
entry = mk_pte(page, vma->vm_page_prot);
if (vma->vm_flags & VM_WRITE)
@@ -2833,10 +2978,10 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
goto unlock_abort;
inc_mm_counter(mm, MM_ANONPAGES);
+ get_page(page);
page_add_new_anon_rmap(page, vma, addr, false);
if (!is_zone_device_page(page))
lru_cache_add_active_or_unevictable(page, vma);
- get_page(page);
if (flush) {
flush_cache_page(vma, addr, pte_pfn(*ptep));
@@ -2850,7 +2995,6 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
}
pte_unmap_unlock(ptep, ptl);
- *src = MIGRATE_PFN_MIGRATE;
return;
unlock_abort:
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 48eb0f1410d4..a852ed2f204c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -686,6 +686,7 @@ void prep_compound_page(struct page *page, unsigned int order)
if (hpage_pincount_available(page))
atomic_set(compound_pincount_ptr(page), 0);
}
+EXPORT_SYMBOL_GPL(prep_compound_page);
#ifdef CONFIG_DEBUG_PAGEALLOC
unsigned int _debug_guardpage_minorder;
--
2.20.1
