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pagemap: introduce pagemap_entry_t without pmshift bits
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These bits are always constant (== PAGE_SHIFT) and just occupy space in
the entry.  Moreover, in next patch we will need to report one more bit
in the pagemap, but all bits are already busy on it.

That said, describe the pagemap entry that has 6 more free zero bits.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Pavel Emelyanov authored and Linus Torvalds committed Jul 3, 2013
1 parent af9de7e commit 2b0a9f0
Showing 1 changed file with 22 additions and 18 deletions.
40 changes: 22 additions & 18 deletions fs/proc/task_mmu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -807,6 +807,7 @@ typedef struct {
struct pagemapread {
int pos, len;
pagemap_entry_t *buffer;
bool v2;
};

#define PAGEMAP_WALK_SIZE (PMD_SIZE)
Expand All @@ -820,14 +821,16 @@ struct pagemapread {
#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_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_PRESENT PM_STATUS(4LL)
#define PM_SWAP PM_STATUS(2LL)
#define PM_FILE PM_STATUS(1LL)
#define PM_NOT_PRESENT PM_PSHIFT(PAGE_SHIFT)
#define PM_NOT_PRESENT(v2) PM_STATUS2(v2, 0)
#define PM_END_OF_BUFFER 1

static inline pagemap_entry_t make_pme(u64 val)
Expand All @@ -850,7 +853,7 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end,
struct pagemapread *pm = walk->private;
unsigned long addr;
int err = 0;
pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));

for (addr = start; addr < end; addr += PAGE_SIZE) {
err = add_to_pagemap(addr, &pme, pm);
Expand All @@ -860,7 +863,7 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end,
return err;
}

static void pte_to_pagemap_entry(pagemap_entry_t *pme,
static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
u64 frame, flags;
Expand All @@ -879,18 +882,18 @@ static void pte_to_pagemap_entry(pagemap_entry_t *pme,
if (is_migration_entry(entry))
page = migration_entry_to_page(entry);
} else {
*pme = make_pme(PM_NOT_PRESENT);
*pme = make_pme(PM_NOT_PRESENT(pm->v2));
return;
}

if (page && !PageAnon(page))
flags |= PM_FILE;

*pme = make_pme(PM_PFRAME(frame) | PM_PSHIFT(PAGE_SHIFT) | flags);
*pme = make_pme(PM_PFRAME(frame) | PM_STATUS2(pm->v2, 0) | flags);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pmd_t pmd, int offset)
{
/*
Expand All @@ -900,12 +903,12 @@ static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
*/
if (pmd_present(pmd))
*pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
| PM_STATUS2(pm->v2, 0) | PM_PRESENT);
else
*pme = make_pme(PM_NOT_PRESENT);
*pme = make_pme(PM_NOT_PRESENT(pm->v2));
}
#else
static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pmd_t pmd, int offset)
{
}
Expand All @@ -918,7 +921,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct pagemapread *pm = walk->private;
pte_t *pte;
int err = 0;
pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));

/* find the first VMA at or above 'addr' */
vma = find_vma(walk->mm, addr);
Expand All @@ -928,7 +931,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,

offset = (addr & ~PAGEMAP_WALK_MASK) >>
PAGE_SHIFT;
thp_pmd_to_pagemap_entry(&pme, *pmd, offset);
thp_pmd_to_pagemap_entry(&pme, pm, *pmd, offset);
err = add_to_pagemap(addr, &pme, pm);
if (err)
break;
Expand All @@ -945,15 +948,15 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
* and need a new, higher one */
if (vma && (addr >= vma->vm_end)) {
vma = find_vma(walk->mm, addr);
pme = make_pme(PM_NOT_PRESENT);
pme = make_pme(PM_NOT_PRESENT(pm->v2));
}

/* check that 'vma' actually covers this address,
* and that it isn't a huge page vma */
if (vma && (vma->vm_start <= addr) &&
!is_vm_hugetlb_page(vma)) {
pte = pte_offset_map(pmd, addr);
pte_to_pagemap_entry(&pme, vma, addr, *pte);
pte_to_pagemap_entry(&pme, pm, vma, addr, *pte);
/* unmap before userspace copy */
pte_unmap(pte);
}
Expand All @@ -968,14 +971,14 @@ 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,
static void huge_pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pte_t pte, int offset)
{
if (pte_present(pte))
*pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset)
| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
| PM_STATUS2(pm->v2, 0) | PM_PRESENT);
else
*pme = make_pme(PM_NOT_PRESENT);
*pme = make_pme(PM_NOT_PRESENT(pm->v2));
}

/* This function walks within one hugetlb entry in the single call */
Expand All @@ -989,7 +992,7 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,

for (; addr != end; addr += PAGE_SIZE) {
int offset = (addr & ~hmask) >> PAGE_SHIFT;
huge_pte_to_pagemap_entry(&pme, *pte, offset);
huge_pte_to_pagemap_entry(&pme, pm, *pte, offset);
err = add_to_pagemap(addr, &pme, pm);
if (err)
return err;
Expand Down Expand Up @@ -1051,6 +1054,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!count)
goto out_task;

pm.v2 = false;
pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
ret = -ENOMEM;
Expand Down

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