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pagemap: switch to the new format and do some cleanup
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This patch removes page-shift bits (scheduled to remove since 3.11) and
completes migration to the new bit layout.  Also it cleans messy macro.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mark Williamson <mwilliamson@undo-software.com>
Tested-by:  Mark Williamson <mwilliamson@undo-software.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Konstantin Khlebnikov authored and Linus Torvalds committed Sep 8, 2015
1 parent a06db75 commit deb9454
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Showing 2 changed files with 61 additions and 114 deletions.
150 changes: 53 additions & 97 deletions fs/proc/task_mmu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -712,23 +712,6 @@ const struct file_operations proc_tid_smaps_operations = {
.release = proc_map_release,
};

/*
* We do not want to have constant page-shift bits sitting in
* pagemap entries and are about to reuse them some time soon.
*
* Here's the "migration strategy":
* 1. when the system boots these bits remain what they are,
* but a warning about future change is printed in log;
* 2. once anyone clears soft-dirty bits via clear_refs file,
* these flag is set to denote, that user is aware of the
* new API and those page-shift bits change their meaning.
* The respective warning is printed in dmesg;
* 3. In a couple of releases we will remove all the mentions
* of page-shift in pagemap entries.
*/

static bool soft_dirty_cleared __read_mostly;

enum clear_refs_types {
CLEAR_REFS_ALL = 1,
CLEAR_REFS_ANON,
Expand Down Expand Up @@ -889,13 +872,6 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
return -EINVAL;

if (type == CLEAR_REFS_SOFT_DIRTY) {
soft_dirty_cleared = true;
pr_warn_once("The pagemap bits 55-60 has changed their meaning!"
" See the linux/Documentation/vm/pagemap.txt for "
"details.\n");
}

task = get_proc_task(file_inode(file));
if (!task)
return -ESRCH;
Expand Down Expand Up @@ -963,36 +939,24 @@ typedef struct {
struct pagemapread {
int pos, len; /* units: PM_ENTRY_BYTES, not bytes */
pagemap_entry_t *buffer;
bool v2;
};

#define PAGEMAP_WALK_SIZE (PMD_SIZE)
#define PAGEMAP_WALK_MASK (PMD_MASK)

#define PM_ENTRY_BYTES sizeof(pagemap_entry_t)
#define PM_STATUS_BITS 3
#define PM_STATUS_OFFSET (64 - PM_STATUS_BITS)
#define PM_STATUS_MASK (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
#define PM_STATUS(nr) (((nr) << PM_STATUS_OFFSET) & PM_STATUS_MASK)
#define PM_PSHIFT_BITS 6
#define PM_PSHIFT_OFFSET (PM_STATUS_OFFSET - PM_PSHIFT_BITS)
#define PM_PSHIFT_MASK (((1LL << PM_PSHIFT_BITS) - 1) << PM_PSHIFT_OFFSET)
#define __PM_PSHIFT(x) (((u64) (x) << PM_PSHIFT_OFFSET) & PM_PSHIFT_MASK)
#define PM_PFRAME_MASK ((1LL << PM_PSHIFT_OFFSET) - 1)
#define PM_PFRAME(x) ((x) & PM_PFRAME_MASK)
/* in "new" pagemap pshift bits are occupied with more status bits */
#define PM_STATUS2(v2, x) (__PM_PSHIFT(v2 ? x : PAGE_SHIFT))

#define __PM_SOFT_DIRTY (1LL)
#define PM_PRESENT PM_STATUS(4LL)
#define PM_SWAP PM_STATUS(2LL)
#define PM_FILE PM_STATUS(1LL)
#define PM_NOT_PRESENT(v2) PM_STATUS2(v2, 0)
#define PM_ENTRY_BYTES sizeof(pagemap_entry_t)
#define PM_PFRAME_BITS 55
#define PM_PFRAME_MASK GENMASK_ULL(PM_PFRAME_BITS - 1, 0)
#define PM_SOFT_DIRTY BIT_ULL(55)
#define PM_FILE BIT_ULL(61)
#define PM_SWAP BIT_ULL(62)
#define PM_PRESENT BIT_ULL(63)

#define PM_END_OF_BUFFER 1

static inline pagemap_entry_t make_pme(u64 val)
static inline pagemap_entry_t make_pme(u64 frame, u64 flags)
{
return (pagemap_entry_t) { .pme = val };
return (pagemap_entry_t) { .pme = (frame & PM_PFRAME_MASK) | flags };
}

static int add_to_pagemap(unsigned long addr, pagemap_entry_t *pme,
Expand All @@ -1013,7 +977,7 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end,

while (addr < end) {
struct vm_area_struct *vma = find_vma(walk->mm, addr);
pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));
pagemap_entry_t pme = make_pme(0, 0);
/* End of address space hole, which we mark as non-present. */
unsigned long hole_end;

Expand All @@ -1033,7 +997,7 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end,

/* Addresses in the VMA. */
if (vma->vm_flags & VM_SOFTDIRTY)
pme.pme |= PM_STATUS2(pm->v2, __PM_SOFT_DIRTY);
pme = make_pme(0, PM_SOFT_DIRTY);
for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) {
err = add_to_pagemap(addr, &pme, pm);
if (err)
Expand All @@ -1044,63 +1008,61 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end,
return err;
}

static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
u64 frame, flags;
u64 frame = 0, flags = 0;
struct page *page = NULL;
int flags2 = 0;

if (pte_present(pte)) {
frame = pte_pfn(pte);
flags = PM_PRESENT;
flags |= PM_PRESENT;
page = vm_normal_page(vma, addr, pte);
if (pte_soft_dirty(pte))
flags2 |= __PM_SOFT_DIRTY;
flags |= PM_SOFT_DIRTY;
} else if (is_swap_pte(pte)) {
swp_entry_t entry;
if (pte_swp_soft_dirty(pte))
flags2 |= __PM_SOFT_DIRTY;
flags |= PM_SOFT_DIRTY;
entry = pte_to_swp_entry(pte);
frame = swp_type(entry) |
(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
flags = PM_SWAP;
flags |= PM_SWAP;
if (is_migration_entry(entry))
page = migration_entry_to_page(entry);
} else {
if (vma->vm_flags & VM_SOFTDIRTY)
flags2 |= __PM_SOFT_DIRTY;
*pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, flags2));
return;
}

if (page && !PageAnon(page))
flags |= PM_FILE;
if ((vma->vm_flags & VM_SOFTDIRTY))
flags2 |= __PM_SOFT_DIRTY;
if (vma->vm_flags & VM_SOFTDIRTY)
flags |= PM_SOFT_DIRTY;

*pme = make_pme(PM_PFRAME(frame) | PM_STATUS2(pm->v2, flags2) | flags);
return make_pme(frame, flags);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pmd_t pmd, int offset, int pmd_flags2)
static pagemap_entry_t thp_pmd_to_pagemap_entry(struct pagemapread *pm,
pmd_t pmd, int offset, u64 flags)
{
u64 frame = 0;

/*
* Currently pmd for thp is always present because thp can not be
* swapped-out, migrated, or HWPOISONed (split in such cases instead.)
* This if-check is just to prepare for future implementation.
*/
if (pmd_present(pmd))
*pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
| PM_STATUS2(pm->v2, pmd_flags2) | PM_PRESENT);
else
*pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, pmd_flags2));
if (pmd_present(pmd)) {
frame = pmd_pfn(pmd) + offset;
flags |= PM_PRESENT;
}

return make_pme(frame, flags);
}
#else
static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pmd_t pmd, int offset, int pmd_flags2)
static pagemap_entry_t thp_pmd_to_pagemap_entry(struct pagemapread *pm,
pmd_t pmd, int offset, u64 flags)
{
return make_pme(0, 0);
}
#endif

Expand All @@ -1114,20 +1076,18 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
int err = 0;

if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
int pmd_flags2;
u64 flags = 0;

if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(*pmd))
pmd_flags2 = __PM_SOFT_DIRTY;
else
pmd_flags2 = 0;
flags |= PM_SOFT_DIRTY;

for (; addr != end; addr += PAGE_SIZE) {
unsigned long offset;
pagemap_entry_t pme;

offset = (addr & ~PAGEMAP_WALK_MASK) >>
PAGE_SHIFT;
thp_pmd_to_pagemap_entry(&pme, pm, *pmd, offset, pmd_flags2);
pme = thp_pmd_to_pagemap_entry(pm, *pmd, offset, flags);
err = add_to_pagemap(addr, &pme, pm);
if (err)
break;
Expand All @@ -1147,7 +1107,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
for (; addr < end; pte++, addr += PAGE_SIZE) {
pagemap_entry_t pme;

pte_to_pagemap_entry(&pme, pm, vma, addr, *pte);
pme = pte_to_pagemap_entry(pm, vma, addr, *pte);
err = add_to_pagemap(addr, &pme, pm);
if (err)
break;
Expand All @@ -1160,16 +1120,17 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
}

#ifdef CONFIG_HUGETLB_PAGE
static void huge_pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pte_t pte, int offset, int flags2)
static pagemap_entry_t huge_pte_to_pagemap_entry(struct pagemapread *pm,
pte_t pte, int offset, u64 flags)
{
if (pte_present(pte))
*pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset) |
PM_STATUS2(pm->v2, flags2) |
PM_PRESENT);
else
*pme = make_pme(PM_NOT_PRESENT(pm->v2) |
PM_STATUS2(pm->v2, flags2));
u64 frame = 0;

if (pte_present(pte)) {
frame = pte_pfn(pte) + offset;
flags |= PM_PRESENT;
}

return make_pme(frame, flags);
}

/* This function walks within one hugetlb entry in the single call */
Expand All @@ -1180,17 +1141,15 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
struct pagemapread *pm = walk->private;
struct vm_area_struct *vma = walk->vma;
int err = 0;
int flags2;
u64 flags = 0;
pagemap_entry_t pme;

if (vma->vm_flags & VM_SOFTDIRTY)
flags2 = __PM_SOFT_DIRTY;
else
flags2 = 0;
flags |= PM_SOFT_DIRTY;

for (; addr != end; addr += PAGE_SIZE) {
int offset = (addr & ~hmask) >> PAGE_SHIFT;
huge_pte_to_pagemap_entry(&pme, pm, *pte, offset, flags2);
pme = huge_pte_to_pagemap_entry(pm, *pte, offset, flags);
err = add_to_pagemap(addr, &pme, pm);
if (err)
return err;
Expand All @@ -1211,7 +1170,8 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
* Bits 0-54 page frame number (PFN) if present
* Bits 0-4 swap type if swapped
* Bits 5-54 swap offset if swapped
* Bits 55-60 page shift (page size = 1<<page shift)
* Bit 55 pte is soft-dirty (see Documentation/vm/soft-dirty.txt)
* Bits 56-60 zero
* Bit 61 page is file-page or shared-anon
* Bit 62 page swapped
* Bit 63 page present
Expand Down Expand Up @@ -1250,7 +1210,6 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!count)
goto out_mm;

pm.v2 = soft_dirty_cleared;
pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
ret = -ENOMEM;
Expand Down Expand Up @@ -1323,9 +1282,6 @@ static int pagemap_open(struct inode *inode, struct file *file)
/* do not disclose physical addresses: attack vector */
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about "
"to stop being page-shift some time soon. See the "
"linux/Documentation/vm/pagemap.txt for details.\n");

mm = proc_mem_open(inode, PTRACE_MODE_READ);
if (IS_ERR(mm))
Expand Down
25 changes: 8 additions & 17 deletions tools/vm/page-types.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -57,23 +57,14 @@
* pagemap kernel ABI bits
*/

#define PM_ENTRY_BYTES sizeof(uint64_t)
#define PM_STATUS_BITS 3
#define PM_STATUS_OFFSET (64 - PM_STATUS_BITS)
#define PM_STATUS_MASK (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
#define PM_STATUS(nr) (((nr) << PM_STATUS_OFFSET) & PM_STATUS_MASK)
#define PM_PSHIFT_BITS 6
#define PM_PSHIFT_OFFSET (PM_STATUS_OFFSET - PM_PSHIFT_BITS)
#define PM_PSHIFT_MASK (((1LL << PM_PSHIFT_BITS) - 1) << PM_PSHIFT_OFFSET)
#define __PM_PSHIFT(x) (((uint64_t) (x) << PM_PSHIFT_OFFSET) & PM_PSHIFT_MASK)
#define PM_PFRAME_MASK ((1LL << PM_PSHIFT_OFFSET) - 1)
#define PM_PFRAME(x) ((x) & PM_PFRAME_MASK)

#define __PM_SOFT_DIRTY (1LL)
#define PM_PRESENT PM_STATUS(4LL)
#define PM_SWAP PM_STATUS(2LL)
#define PM_SOFT_DIRTY __PM_PSHIFT(__PM_SOFT_DIRTY)

#define PM_ENTRY_BYTES 8
#define PM_PFRAME_BITS 55
#define PM_PFRAME_MASK ((1LL << PM_PFRAME_BITS) - 1)
#define PM_PFRAME(x) ((x) & PM_PFRAME_MASK)
#define PM_SOFT_DIRTY (1ULL << 55)
#define PM_FILE (1ULL << 61)
#define PM_SWAP (1ULL << 62)
#define PM_PRESENT (1ULL << 63)

/*
* kernel page flags
Expand Down

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