forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
322 lines
8.7 KiB
322 lines
8.7 KiB
// SPDX-License-Identifier: GPL-2.0 |
|
#include <linux/mm.h> |
|
#include <linux/rmap.h> |
|
#include <linux/hugetlb.h> |
|
#include <linux/swap.h> |
|
#include <linux/swapops.h> |
|
|
|
#include "internal.h" |
|
|
|
static inline bool not_found(struct page_vma_mapped_walk *pvmw) |
|
{ |
|
page_vma_mapped_walk_done(pvmw); |
|
return false; |
|
} |
|
|
|
static bool map_pte(struct page_vma_mapped_walk *pvmw) |
|
{ |
|
pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address); |
|
if (!(pvmw->flags & PVMW_SYNC)) { |
|
if (pvmw->flags & PVMW_MIGRATION) { |
|
if (!is_swap_pte(*pvmw->pte)) |
|
return false; |
|
} else { |
|
/* |
|
* We get here when we are trying to unmap a private |
|
* device page from the process address space. Such |
|
* page is not CPU accessible and thus is mapped as |
|
* a special swap entry, nonetheless it still does |
|
* count as a valid regular mapping for the page (and |
|
* is accounted as such in page maps count). |
|
* |
|
* So handle this special case as if it was a normal |
|
* page mapping ie lock CPU page table and returns |
|
* true. |
|
* |
|
* For more details on device private memory see HMM |
|
* (include/linux/hmm.h or mm/hmm.c). |
|
*/ |
|
if (is_swap_pte(*pvmw->pte)) { |
|
swp_entry_t entry; |
|
|
|
/* Handle un-addressable ZONE_DEVICE memory */ |
|
entry = pte_to_swp_entry(*pvmw->pte); |
|
if (!is_device_private_entry(entry) && |
|
!is_device_exclusive_entry(entry)) |
|
return false; |
|
} else if (!pte_present(*pvmw->pte)) |
|
return false; |
|
} |
|
} |
|
pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); |
|
spin_lock(pvmw->ptl); |
|
return true; |
|
} |
|
|
|
static inline bool pfn_is_match(struct page *page, unsigned long pfn) |
|
{ |
|
unsigned long page_pfn = page_to_pfn(page); |
|
|
|
/* normal page and hugetlbfs page */ |
|
if (!PageTransCompound(page) || PageHuge(page)) |
|
return page_pfn == pfn; |
|
|
|
/* THP can be referenced by any subpage */ |
|
return pfn >= page_pfn && pfn - page_pfn < thp_nr_pages(page); |
|
} |
|
|
|
/** |
|
* check_pte - check if @pvmw->page is mapped at the @pvmw->pte |
|
* @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking |
|
* |
|
* page_vma_mapped_walk() found a place where @pvmw->page is *potentially* |
|
* mapped. check_pte() has to validate this. |
|
* |
|
* pvmw->pte may point to empty PTE, swap PTE or PTE pointing to |
|
* arbitrary page. |
|
* |
|
* If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration |
|
* entry that points to @pvmw->page or any subpage in case of THP. |
|
* |
|
* If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to |
|
* pvmw->page or any subpage in case of THP. |
|
* |
|
* Otherwise, return false. |
|
* |
|
*/ |
|
static bool check_pte(struct page_vma_mapped_walk *pvmw) |
|
{ |
|
unsigned long pfn; |
|
|
|
if (pvmw->flags & PVMW_MIGRATION) { |
|
swp_entry_t entry; |
|
if (!is_swap_pte(*pvmw->pte)) |
|
return false; |
|
entry = pte_to_swp_entry(*pvmw->pte); |
|
|
|
if (!is_migration_entry(entry) && |
|
!is_device_exclusive_entry(entry)) |
|
return false; |
|
|
|
pfn = swp_offset(entry); |
|
} else if (is_swap_pte(*pvmw->pte)) { |
|
swp_entry_t entry; |
|
|
|
/* Handle un-addressable ZONE_DEVICE memory */ |
|
entry = pte_to_swp_entry(*pvmw->pte); |
|
if (!is_device_private_entry(entry) && |
|
!is_device_exclusive_entry(entry)) |
|
return false; |
|
|
|
pfn = swp_offset(entry); |
|
} else { |
|
if (!pte_present(*pvmw->pte)) |
|
return false; |
|
|
|
pfn = pte_pfn(*pvmw->pte); |
|
} |
|
|
|
return pfn_is_match(pvmw->page, pfn); |
|
} |
|
|
|
static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size) |
|
{ |
|
pvmw->address = (pvmw->address + size) & ~(size - 1); |
|
if (!pvmw->address) |
|
pvmw->address = ULONG_MAX; |
|
} |
|
|
|
/** |
|
* page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at |
|
* @pvmw->address |
|
* @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags |
|
* must be set. pmd, pte and ptl must be NULL. |
|
* |
|
* Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point |
|
* to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is |
|
* adjusted if needed (for PTE-mapped THPs). |
|
* |
|
* If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page |
|
* (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in |
|
* a loop to find all PTEs that map the THP. |
|
* |
|
* For HugeTLB pages, @pvmw->pte is set to the relevant page table entry |
|
* regardless of which page table level the page is mapped at. @pvmw->pmd is |
|
* NULL. |
|
* |
|
* Returns false if there are no more page table entries for the page in |
|
* the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. |
|
* |
|
* If you need to stop the walk before page_vma_mapped_walk() returned false, |
|
* use page_vma_mapped_walk_done(). It will do the housekeeping. |
|
*/ |
|
bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) |
|
{ |
|
struct mm_struct *mm = pvmw->vma->vm_mm; |
|
struct page *page = pvmw->page; |
|
unsigned long end; |
|
pgd_t *pgd; |
|
p4d_t *p4d; |
|
pud_t *pud; |
|
pmd_t pmde; |
|
|
|
/* The only possible pmd mapping has been handled on last iteration */ |
|
if (pvmw->pmd && !pvmw->pte) |
|
return not_found(pvmw); |
|
|
|
if (unlikely(PageHuge(page))) { |
|
/* The only possible mapping was handled on last iteration */ |
|
if (pvmw->pte) |
|
return not_found(pvmw); |
|
|
|
/* when pud is not present, pte will be NULL */ |
|
pvmw->pte = huge_pte_offset(mm, pvmw->address, page_size(page)); |
|
if (!pvmw->pte) |
|
return false; |
|
|
|
pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); |
|
spin_lock(pvmw->ptl); |
|
if (!check_pte(pvmw)) |
|
return not_found(pvmw); |
|
return true; |
|
} |
|
|
|
/* |
|
* Seek to next pte only makes sense for THP. |
|
* But more important than that optimization, is to filter out |
|
* any PageKsm page: whose page->index misleads vma_address() |
|
* and vma_address_end() to disaster. |
|
*/ |
|
end = PageTransCompound(page) ? |
|
vma_address_end(page, pvmw->vma) : |
|
pvmw->address + PAGE_SIZE; |
|
if (pvmw->pte) |
|
goto next_pte; |
|
restart: |
|
do { |
|
pgd = pgd_offset(mm, pvmw->address); |
|
if (!pgd_present(*pgd)) { |
|
step_forward(pvmw, PGDIR_SIZE); |
|
continue; |
|
} |
|
p4d = p4d_offset(pgd, pvmw->address); |
|
if (!p4d_present(*p4d)) { |
|
step_forward(pvmw, P4D_SIZE); |
|
continue; |
|
} |
|
pud = pud_offset(p4d, pvmw->address); |
|
if (!pud_present(*pud)) { |
|
step_forward(pvmw, PUD_SIZE); |
|
continue; |
|
} |
|
|
|
pvmw->pmd = pmd_offset(pud, pvmw->address); |
|
/* |
|
* Make sure the pmd value isn't cached in a register by the |
|
* compiler and used as a stale value after we've observed a |
|
* subsequent update. |
|
*/ |
|
pmde = READ_ONCE(*pvmw->pmd); |
|
|
|
if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) { |
|
pvmw->ptl = pmd_lock(mm, pvmw->pmd); |
|
pmde = *pvmw->pmd; |
|
if (likely(pmd_trans_huge(pmde))) { |
|
if (pvmw->flags & PVMW_MIGRATION) |
|
return not_found(pvmw); |
|
if (pmd_page(pmde) != page) |
|
return not_found(pvmw); |
|
return true; |
|
} |
|
if (!pmd_present(pmde)) { |
|
swp_entry_t entry; |
|
|
|
if (!thp_migration_supported() || |
|
!(pvmw->flags & PVMW_MIGRATION)) |
|
return not_found(pvmw); |
|
entry = pmd_to_swp_entry(pmde); |
|
if (!is_migration_entry(entry) || |
|
pfn_swap_entry_to_page(entry) != page) |
|
return not_found(pvmw); |
|
return true; |
|
} |
|
/* THP pmd was split under us: handle on pte level */ |
|
spin_unlock(pvmw->ptl); |
|
pvmw->ptl = NULL; |
|
} else if (!pmd_present(pmde)) { |
|
/* |
|
* If PVMW_SYNC, take and drop THP pmd lock so that we |
|
* cannot return prematurely, while zap_huge_pmd() has |
|
* cleared *pmd but not decremented compound_mapcount(). |
|
*/ |
|
if ((pvmw->flags & PVMW_SYNC) && |
|
PageTransCompound(page)) { |
|
spinlock_t *ptl = pmd_lock(mm, pvmw->pmd); |
|
|
|
spin_unlock(ptl); |
|
} |
|
step_forward(pvmw, PMD_SIZE); |
|
continue; |
|
} |
|
if (!map_pte(pvmw)) |
|
goto next_pte; |
|
this_pte: |
|
if (check_pte(pvmw)) |
|
return true; |
|
next_pte: |
|
do { |
|
pvmw->address += PAGE_SIZE; |
|
if (pvmw->address >= end) |
|
return not_found(pvmw); |
|
/* Did we cross page table boundary? */ |
|
if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) { |
|
if (pvmw->ptl) { |
|
spin_unlock(pvmw->ptl); |
|
pvmw->ptl = NULL; |
|
} |
|
pte_unmap(pvmw->pte); |
|
pvmw->pte = NULL; |
|
goto restart; |
|
} |
|
pvmw->pte++; |
|
if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) { |
|
pvmw->ptl = pte_lockptr(mm, pvmw->pmd); |
|
spin_lock(pvmw->ptl); |
|
} |
|
} while (pte_none(*pvmw->pte)); |
|
|
|
if (!pvmw->ptl) { |
|
pvmw->ptl = pte_lockptr(mm, pvmw->pmd); |
|
spin_lock(pvmw->ptl); |
|
} |
|
goto this_pte; |
|
} while (pvmw->address < end); |
|
|
|
return false; |
|
} |
|
|
|
/** |
|
* page_mapped_in_vma - check whether a page is really mapped in a VMA |
|
* @page: the page to test |
|
* @vma: the VMA to test |
|
* |
|
* Returns 1 if the page is mapped into the page tables of the VMA, 0 |
|
* if the page is not mapped into the page tables of this VMA. Only |
|
* valid for normal file or anonymous VMAs. |
|
*/ |
|
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) |
|
{ |
|
struct page_vma_mapped_walk pvmw = { |
|
.page = page, |
|
.vma = vma, |
|
.flags = PVMW_SYNC, |
|
}; |
|
|
|
pvmw.address = vma_address(page, vma); |
|
if (pvmw.address == -EFAULT) |
|
return 0; |
|
if (!page_vma_mapped_walk(&pvmw)) |
|
return 0; |
|
page_vma_mapped_walk_done(&pvmw); |
|
return 1; |
|
}
|
|
|