[PATCHv5 08/11] mm, hugetlb: convert hugetlbfs to use split pmd lock

From: Kirill A. Shutemov
Date: Mon Oct 07 2013 - 09:55:03 EST

Hugetlb supports multiple page sizes. We use split lock only for PMD
level, but not for PUD.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Tested-by: Alex Thorlton <athorlton@xxxxxxx>
---
fs/proc/meminfo.c | 2 +-
include/linux/hugetlb.h | 25 +++++++++++
include/linux/swapops.h | 7 ++--
mm/hugetlb.c | 108 +++++++++++++++++++++++++++++-------------------
mm/mempolicy.c | 5 ++-
mm/migrate.c | 7 ++--
mm/rmap.c | 2 +-
7 files changed, 103 insertions(+), 53 deletions(-)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 59d85d6088..6d061f5359 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -1,8 +1,8 @@
#include <linux/fs.h>
-#include <linux/hugetlb.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/hugetlb.h>
#include <linux/mman.h>
#include <linux/mmzone.h>
#include <linux/proc_fs.h>
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0393270466..2132532b02 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -392,6 +392,15 @@ static inline int hugepage_migration_support(struct hstate *h)
return pmd_huge_support() && (huge_page_shift(h) == PMD_SHIFT);
}

+static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
+ struct mm_struct *mm, pte_t *pte)
+{
+ if (huge_page_size(h) == PMD_SIZE)
+ return pmd_lockptr(mm, (pmd_t *) pte);
+ VM_BUG_ON(huge_page_size(h) == PAGE_SIZE);
+ return &mm->page_table_lock;
+}
+
#else /* CONFIG_HUGETLB_PAGE */
struct hstate {};
#define alloc_huge_page_node(h, nid) NULL
@@ -401,6 +410,7 @@ struct hstate {};
#define hstate_sizelog(s) NULL
#define hstate_vma(v) NULL
#define hstate_inode(i) NULL
+#define page_hstate(page) NULL
#define huge_page_size(h) PAGE_SIZE
#define huge_page_mask(h) PAGE_MASK
#define vma_kernel_pagesize(v) PAGE_SIZE
@@ -421,6 +431,21 @@ static inline pgoff_t basepage_index(struct page *page)
#define dissolve_free_huge_pages(s, e) do {} while (0)
#define pmd_huge_support() 0
#define hugepage_migration_support(h) 0
+
+static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
+ struct mm_struct *mm, pte_t *pte)
+{
+ return &mm->page_table_lock;
+}
#endif /* CONFIG_HUGETLB_PAGE */

+static inline spinlock_t *huge_pte_lock(struct hstate *h,
+ struct mm_struct *mm, pte_t *pte)
+{
+ spinlock_t *ptl;
+ ptl = huge_pte_lockptr(h, mm, pte);
+ spin_lock(ptl);
+ return ptl;
+}
+
#endif /* _LINUX_HUGETLB_H */
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 8d4fa82bfb..c0f75261a7 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -139,7 +139,8 @@ static inline void make_migration_entry_read(swp_entry_t *entry)

extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address);
-extern void migration_entry_wait_huge(struct mm_struct *mm, pte_t *pte);
+extern void migration_entry_wait_huge(struct vm_area_struct *vma,
+ struct mm_struct *mm, pte_t *pte);
#else

#define make_migration_entry(page, write) swp_entry(0, 0)
@@ -151,8 +152,8 @@ static inline int is_migration_entry(swp_entry_t swp)
static inline void make_migration_entry_read(swp_entry_t *entryp) { }
static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address) { }
-static inline void migration_entry_wait_huge(struct mm_struct *mm,
- pte_t *pte) { }
+static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
+ struct mm_struct *mm, pte_t *pte) { }
static inline int is_write_migration_entry(swp_entry_t entry)
{
return 0;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b49579c7f2..1c13a6f8d8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2361,6 +2361,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;

for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
+ spinlock_t *src_ptl, *dst_ptl;
src_pte = huge_pte_offset(src, addr);
if (!src_pte)
continue;
@@ -2372,8 +2373,9 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
if (dst_pte == src_pte)
continue;

- spin_lock(&dst->page_table_lock);
- spin_lock_nested(&src->page_table_lock, SINGLE_DEPTH_NESTING);
+ dst_ptl = huge_pte_lock(h, dst, dst_pte);
+ src_ptl = huge_pte_lockptr(h, src, src_pte);
+ spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
if (!huge_pte_none(huge_ptep_get(src_pte))) {
if (cow)
huge_ptep_set_wrprotect(src, addr, src_pte);
@@ -2383,8 +2385,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
page_dup_rmap(ptepage);
set_huge_pte_at(dst, addr, dst_pte, entry);
}
- spin_unlock(&src->page_table_lock);
- spin_unlock(&dst->page_table_lock);
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
}
return 0;

@@ -2427,6 +2429,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long address;
pte_t *ptep;
pte_t pte;
+ spinlock_t *ptl;
struct page *page;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
@@ -2440,25 +2443,25 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
tlb_start_vma(tlb, vma);
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
again:
- spin_lock(&mm->page_table_lock);
for (address = start; address < end; address += sz) {
ptep = huge_pte_offset(mm, address);
if (!ptep)
continue;

+ ptl = huge_pte_lock(h, mm, ptep);
if (huge_pmd_unshare(mm, &address, ptep))
- continue;
+ goto unlock;

pte = huge_ptep_get(ptep);
if (huge_pte_none(pte))
- continue;
+ goto unlock;

/*
* HWPoisoned hugepage is already unmapped and dropped reference
*/
if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
huge_pte_clear(mm, address, ptep);
- continue;
+ goto unlock;
}

page = pte_page(pte);
@@ -2469,7 +2472,7 @@ again:
*/
if (ref_page) {
if (page != ref_page)
- continue;
+ goto unlock;

/*
* Mark the VMA as having unmapped its page so that
@@ -2486,13 +2489,18 @@ again:

page_remove_rmap(page);
force_flush = !__tlb_remove_page(tlb, page);
- if (force_flush)
+ if (force_flush) {
+ spin_unlock(ptl);
break;
+ }
/* Bail out after unmapping reference page if supplied */
- if (ref_page)
+ if (ref_page) {
+ spin_unlock(ptl);
break;
+ }
+unlock:
+ spin_unlock(ptl);
}
- spin_unlock(&mm->page_table_lock);
/*
* mmu_gather ran out of room to batch pages, we break out of
* the PTE lock to avoid doing the potential expensive TLB invalidate
@@ -2598,7 +2606,7 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
*/
static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *ptep, pte_t pte,
- struct page *pagecache_page)
+ struct page *pagecache_page, spinlock_t *ptl)
{
struct hstate *h = hstate_vma(vma);
struct page *old_page, *new_page;
@@ -2632,8 +2640,8 @@ retry_avoidcopy:

page_cache_get(old_page);

- /* Drop page_table_lock as buddy allocator may be called */
- spin_unlock(&mm->page_table_lock);
+ /* Drop page table lock as buddy allocator may be called */
+ spin_unlock(ptl);
new_page = alloc_huge_page(vma, address, outside_reserve);

if (IS_ERR(new_page)) {
@@ -2651,12 +2659,12 @@ retry_avoidcopy:
BUG_ON(huge_pte_none(pte));
if (unmap_ref_private(mm, vma, old_page, address)) {
BUG_ON(huge_pte_none(pte));
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte)))
goto retry_avoidcopy;
/*
- * race occurs while re-acquiring page_table_lock, and
+ * race occurs while re-acquiring page table lock, and
* our job is done.
*/
return 0;
@@ -2665,7 +2673,7 @@ retry_avoidcopy:
}

/* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
if (err == -ENOMEM)
return VM_FAULT_OOM;
else
@@ -2680,7 +2688,7 @@ retry_avoidcopy:
page_cache_release(new_page);
page_cache_release(old_page);
/* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
return VM_FAULT_OOM;
}

@@ -2692,10 +2700,10 @@ retry_avoidcopy:
mmun_end = mmun_start + huge_page_size(h);
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
/*
- * Retake the page_table_lock to check for racing updates
+ * Retake the page table lock to check for racing updates
* before the page tables are altered
*/
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
ClearPagePrivate(new_page);
@@ -2709,13 +2717,13 @@ retry_avoidcopy:
/* Make the old page be freed below */
new_page = old_page;
}
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
page_cache_release(new_page);
page_cache_release(old_page);

/* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
return 0;
}

@@ -2763,6 +2771,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page *page;
struct address_space *mapping;
pte_t new_pte;
+ spinlock_t *ptl;

/*
* Currently, we are forced to kill the process in the event the
@@ -2849,7 +2858,8 @@ retry:
goto backout_unlocked;
}

- spin_lock(&mm->page_table_lock);
+ ptl = huge_pte_lockptr(h, mm, ptep);
+ spin_lock(ptl);
size = i_size_read(mapping->host) >> huge_page_shift(h);
if (idx >= size)
goto backout;
@@ -2870,16 +2880,16 @@ retry:

if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
/* Optimization, do the COW without a second fault */
- ret = hugetlb_cow(mm, vma, address, ptep, new_pte, page);
+ ret = hugetlb_cow(mm, vma, address, ptep, new_pte, page, ptl);
}

- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
unlock_page(page);
out:
return ret;

backout:
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
backout_unlocked:
unlock_page(page);
put_page(page);
@@ -2891,6 +2901,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
{
pte_t *ptep;
pte_t entry;
+ spinlock_t *ptl;
int ret;
struct page *page = NULL;
struct page *pagecache_page = NULL;
@@ -2903,7 +2914,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (ptep) {
entry = huge_ptep_get(ptep);
if (unlikely(is_hugetlb_entry_migration(entry))) {
- migration_entry_wait_huge(mm, ptep);
+ migration_entry_wait_huge(vma, mm, ptep);
return 0;
} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
return VM_FAULT_HWPOISON_LARGE |
@@ -2959,17 +2970,18 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (page != pagecache_page)
lock_page(page);

- spin_lock(&mm->page_table_lock);
+ ptl = huge_pte_lockptr(h, mm, ptep);
+ spin_lock(ptl);
/* Check for a racing update before calling hugetlb_cow */
if (unlikely(!pte_same(entry, huge_ptep_get(ptep))))
- goto out_page_table_lock;
+ goto out_ptl;


if (flags & FAULT_FLAG_WRITE) {
if (!huge_pte_write(entry)) {
ret = hugetlb_cow(mm, vma, address, ptep, entry,
- pagecache_page);
- goto out_page_table_lock;
+ pagecache_page, ptl);
+ goto out_ptl;
}
entry = huge_pte_mkdirty(entry);
}
@@ -2978,8 +2990,8 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
flags & FAULT_FLAG_WRITE))
update_mmu_cache(vma, address, ptep);

-out_page_table_lock:
- spin_unlock(&mm->page_table_lock);
+out_ptl:
+ spin_unlock(ptl);

if (pagecache_page) {
unlock_page(pagecache_page);
@@ -3005,9 +3017,9 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long remainder = *nr_pages;
struct hstate *h = hstate_vma(vma);

- spin_lock(&mm->page_table_lock);
while (vaddr < vma->vm_end && remainder) {
pte_t *pte;
+ spinlock_t *ptl = NULL;
int absent;
struct page *page;

@@ -3015,8 +3027,12 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make sure we get the
* first, for the page indexing below to work.
+ *
+ * Note that page table lock is not held when pte is null.
*/
pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
+ if (pte)
+ ptl = huge_pte_lock(h, mm, pte);
absent = !pte || huge_pte_none(huge_ptep_get(pte));

/*
@@ -3028,6 +3044,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
if (absent && (flags & FOLL_DUMP) &&
!hugetlbfs_pagecache_present(h, vma, vaddr)) {
+ if (pte)
+ spin_unlock(ptl);
remainder = 0;
break;
}
@@ -3047,10 +3065,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
!huge_pte_write(huge_ptep_get(pte)))) {
int ret;

- spin_unlock(&mm->page_table_lock);
+ if (pte)
+ spin_unlock(ptl);
ret = hugetlb_fault(mm, vma, vaddr,
(flags & FOLL_WRITE) ? FAULT_FLAG_WRITE : 0);
- spin_lock(&mm->page_table_lock);
if (!(ret & VM_FAULT_ERROR))
continue;

@@ -3081,8 +3099,8 @@ same_page:
*/
goto same_page;
}
+ spin_unlock(ptl);
}
- spin_unlock(&mm->page_table_lock);
*nr_pages = remainder;
*position = vaddr;

@@ -3103,13 +3121,15 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
flush_cache_range(vma, address, end);

mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
- spin_lock(&mm->page_table_lock);
for (; address < end; address += huge_page_size(h)) {
+ spinlock_t *ptl;
ptep = huge_pte_offset(mm, address);
if (!ptep)
continue;
+ ptl = huge_pte_lock(h, mm, ptep);
if (huge_pmd_unshare(mm, &address, ptep)) {
pages++;
+ spin_unlock(ptl);
continue;
}
if (!huge_pte_none(huge_ptep_get(ptep))) {
@@ -3119,8 +3139,8 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
set_huge_pte_at(mm, address, ptep, pte);
pages++;
}
+ spin_unlock(ptl);
}
- spin_unlock(&mm->page_table_lock);
/*
* Must flush TLB before releasing i_mmap_mutex: x86's huge_pmd_unshare
* may have cleared our pud entry and done put_page on the page table:
@@ -3283,6 +3303,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
unsigned long saddr;
pte_t *spte = NULL;
pte_t *pte;
+ spinlock_t *ptl;

if (!vma_shareable(vma, addr))
return (pte_t *)pmd_alloc(mm, pud, addr);
@@ -3305,13 +3326,14 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
if (!spte)
goto out;

- spin_lock(&mm->page_table_lock);
+ ptl = huge_pte_lockptr(hstate_vma(vma), mm, spte);
+ spin_lock(ptl);
if (pud_none(*pud))
pud_populate(mm, pud,
(pmd_t *)((unsigned long)spte & PAGE_MASK));
else
put_page(virt_to_page(spte));
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
out:
pte = (pte_t *)pmd_alloc(mm, pud, addr);
mutex_unlock(&mapping->i_mmap_mutex);
@@ -3325,7 +3347,7 @@ out:
* indicated by page_count > 1, unmap is achieved by clearing pud and
* decrementing the ref count. If count == 1, the pte page is not shared.
*
- * called with vma->vm_mm->page_table_lock held.
+ * called with page table lock held.
*
* returns: 1 successfully unmapped a shared pte page
* 0 the underlying pte page is not shared, or it is the last user
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 04729647f3..930a3e64bd 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -525,8 +525,9 @@ static void queue_pages_hugetlb_pmd_range(struct vm_area_struct *vma,
#ifdef CONFIG_HUGETLB_PAGE
int nid;
struct page *page;
+ spinlock_t *ptl;

- spin_lock(&vma->vm_mm->page_table_lock);
+ ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, (pte_t *)pmd);
page = pte_page(huge_ptep_get((pte_t *)pmd));
nid = page_to_nid(page);
if (node_isset(nid, *nodes) == !!(flags & MPOL_MF_INVERT))
@@ -536,7 +537,7 @@ static void queue_pages_hugetlb_pmd_range(struct vm_area_struct *vma,
(flags & MPOL_MF_MOVE && page_mapcount(page) == 1))
isolate_huge_page(page, private);
unlock:
- spin_unlock(&vma->vm_mm->page_table_lock);
+ spin_unlock(ptl);
#else
BUG();
#endif
diff --git a/mm/migrate.c b/mm/migrate.c
index 9c8d5f59d3..0ac0668a08 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -130,7 +130,7 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
ptep = huge_pte_offset(mm, addr);
if (!ptep)
goto out;
- ptl = &mm->page_table_lock;
+ ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);
} else {
pmd = mm_find_pmd(mm, addr);
if (!pmd)
@@ -247,9 +247,10 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
__migration_entry_wait(mm, ptep, ptl);
}

-void migration_entry_wait_huge(struct mm_struct *mm, pte_t *pte)
+void migration_entry_wait_huge(struct vm_area_struct *vma,
+ struct mm_struct *mm, pte_t *pte)
{
- spinlock_t *ptl = &(mm)->page_table_lock;
+ spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
__migration_entry_wait(mm, pte, ptl);
}

diff --git a/mm/rmap.c b/mm/rmap.c
index b59d741dcf..55c8b8dc9f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -601,7 +601,7 @@ pte_t *__page_check_address(struct page *page, struct mm_struct *mm,

if (unlikely(PageHuge(page))) {
pte = huge_pte_offset(mm, address);
- ptl = &mm->page_table_lock;
+ ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
goto check;
}

--
1.8.4.rc3

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