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Message-Id: <20220121075515.79311-3-songmuchun@bytedance.com>
Date: Fri, 21 Jan 2022 15:55:13 +0800
From: Muchun Song <songmuchun@...edance.com>
To: dan.j.williams@...el.com, willy@...radead.org, jack@...e.cz,
viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
apopple@...dia.com, shy828301@...il.com, rcampbell@...dia.com,
hughd@...gle.com, xiyuyang19@...an.edu.cn,
kirill.shutemov@...ux.intel.com, zwisler@...nel.org
Cc: linux-fsdevel@...r.kernel.org, nvdimm@...ts.linux.dev,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Muchun Song <songmuchun@...edance.com>
Subject: [PATCH 3/5] mm: page_vma_mapped: support checking if a pfn is mapped into a vma
page_vma_mapped_walk() is supposed to check if a page is mapped into a vma.
However, not all page frames (e.g. PFN_DEV) have a associated struct page
with it. There is going to be some duplicate codes similar with this function
if someone want to check if a pfn (without a struct page) is mapped into a
vma. So add support for checking if a pfn is mapped into a vma. In the next
patch, the dax will use this new feature.
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
include/linux/rmap.h | 13 +++++++++--
mm/internal.h | 25 +++++++++++++-------
mm/page_vma_mapped.c | 65 +++++++++++++++++++++++++++++++++-------------------
3 files changed, 70 insertions(+), 33 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 221c3c6438a7..7628474732e7 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -204,9 +204,18 @@ int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
#define PVMW_SYNC (1 << 0)
/* Look for migarion entries rather than present PTEs */
#define PVMW_MIGRATION (1 << 1)
+/* Walk the page table by checking the pfn instead of a struct page */
+#define PVMW_PFN_WALK (1 << 2)
struct page_vma_mapped_walk {
- struct page *page;
+ union {
+ struct page *page;
+ struct {
+ unsigned long pfn;
+ unsigned int nr;
+ pgoff_t index;
+ };
+ };
struct vm_area_struct *vma;
unsigned long address;
pmd_t *pmd;
@@ -218,7 +227,7 @@ struct page_vma_mapped_walk {
static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
{
/* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
- if (pvmw->pte && !PageHuge(pvmw->page))
+ if (pvmw->pte && ((pvmw->flags & PVMW_PFN_WALK) || !PageHuge(pvmw->page)))
pte_unmap(pvmw->pte);
if (pvmw->ptl)
spin_unlock(pvmw->ptl);
diff --git a/mm/internal.h b/mm/internal.h
index deb9bda18e59..d6e3e8e1be2d 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -478,25 +478,34 @@ vma_address(struct page *page, struct vm_area_struct *vma)
}
/*
- * Then at what user virtual address will none of the page be found in vma?
- * Assumes that vma_address() already returned a good starting address.
- * If page is a compound head, the entire compound page is considered.
+ * Return the end of user virtual address at the specific offset within
+ * a vma.
*/
static inline unsigned long
-vma_address_end(struct page *page, struct vm_area_struct *vma)
+vma_pgoff_address_end(pgoff_t pgoff, unsigned long nr_pages,
+ struct vm_area_struct *vma)
{
- pgoff_t pgoff;
unsigned long address;
- VM_BUG_ON_PAGE(PageKsm(page), page); /* KSM page->index unusable */
- pgoff = page_to_pgoff(page) + compound_nr(page);
- address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ address = vma->vm_start + ((pgoff + nr_pages - vma->vm_pgoff) << PAGE_SHIFT);
/* Check for address beyond vma (or wrapped through 0?) */
if (address < vma->vm_start || address > vma->vm_end)
address = vma->vm_end;
return address;
}
+/*
+ * Then at what user virtual address will none of the page be found in vma?
+ * Assumes that vma_address() already returned a good starting address.
+ * If page is a compound head, the entire compound page is considered.
+ */
+static inline unsigned long
+vma_address_end(struct page *page, struct vm_area_struct *vma)
+{
+ VM_BUG_ON_PAGE(PageKsm(page), page); /* KSM page->index unusable */
+ return vma_pgoff_address_end(page_to_pgoff(page), compound_nr(page), vma);
+}
+
static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
struct file *fpin)
{
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index f7b331081791..c8819770d457 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -53,10 +53,16 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw)
return true;
}
-static inline bool pfn_is_match(struct page *page, unsigned long pfn)
+static inline bool pfn_is_match(struct page_vma_mapped_walk *pvmw, unsigned long pfn)
{
- unsigned long page_pfn = page_to_pfn(page);
+ struct page *page;
+ unsigned long page_pfn;
+ if (pvmw->flags & PVMW_PFN_WALK)
+ return pfn >= pvmw->pfn && pfn - pvmw->pfn < pvmw->nr;
+
+ page = pvmw->page;
+ page_pfn = page_to_pfn(page);
/* normal page and hugetlbfs page */
if (!PageTransCompound(page) || PageHuge(page))
return page_pfn == pfn;
@@ -116,7 +122,7 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
pfn = pte_pfn(*pvmw->pte);
}
- return pfn_is_match(pvmw->page, pfn);
+ return pfn_is_match(pvmw, pfn);
}
static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
@@ -127,24 +133,24 @@ static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
}
/**
- * 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.
+ * page_vma_mapped_walk - check if @pvmw->page or @pvmw->pfn is mapped in
+ * @pvmw->vma at @pvmw->address
+ * @pvmw: pointer to struct page_vma_mapped_walk. page (or pfn and nr and
+ * index), 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).
+ * Returns true if the page or pfn 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.
+ * (usually THP or Huge DEVMAP). For PMD-mapped page, you should run
+ * page_vma_mapped_walk() in a loop to find all PTEs that map the huge page.
*
* 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
+ * Returns false if there are no more page table entries for the page or pfn 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,
@@ -153,18 +159,27 @@ static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
{
struct mm_struct *mm = pvmw->vma->vm_mm;
- struct page *page = pvmw->page;
+ struct page *page;
unsigned long end;
+ unsigned long pfn;
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t pmde;
+ if (pvmw->flags & PVMW_PFN_WALK) {
+ page = NULL;
+ pfn = pvmw->pfn;
+ } else {
+ page = pvmw->page;
+ pfn = page_to_pfn(page);
+ }
+
/* The only possible pmd mapping has been handled on last iteration */
if (pvmw->pmd && !pvmw->pte)
return not_found(pvmw);
- if (unlikely(PageHuge(page))) {
+ if (unlikely(page && PageHuge(page))) {
/* The only possible mapping was handled on last iteration */
if (pvmw->pte)
return not_found(pvmw);
@@ -187,9 +202,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
* 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 (page)
+ end = PageTransCompound(page) ?
+ vma_address_end(page, pvmw->vma) :
+ pvmw->address + PAGE_SIZE;
+ else
+ end = vma_pgoff_address_end(pvmw->index, pvmw->nr, pvmw->vma);
+
if (pvmw->pte)
goto next_pte;
restart:
@@ -218,13 +237,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
*/
pmde = READ_ONCE(*pvmw->pmd);
- if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
+ if (pmd_leaf(pmde) || is_pmd_migration_entry(pmde)) {
pvmw->ptl = pmd_lock(mm, pvmw->pmd);
pmde = *pvmw->pmd;
- if (likely(pmd_trans_huge(pmde))) {
+ if (likely(pmd_leaf(pmde))) {
if (pvmw->flags & PVMW_MIGRATION)
return not_found(pvmw);
- if (pmd_page(pmde) != page)
+ if (pmd_pfn(pmde) != pfn)
return not_found(pvmw);
return true;
}
@@ -236,7 +255,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
return not_found(pvmw);
entry = pmd_to_swp_entry(pmde);
if (!is_migration_entry(entry) ||
- pfn_swap_entry_to_page(entry) != page)
+ page_to_pfn(pfn_swap_entry_to_page(entry)) != pfn)
return not_found(pvmw);
return true;
}
@@ -249,7 +268,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
* cannot return prematurely, while zap_huge_pmd() has
* cleared *pmd but not decremented compound_mapcount().
*/
- if ((pvmw->flags & PVMW_SYNC) &&
+ if ((pvmw->flags & PVMW_SYNC) && page &&
PageTransCompound(page)) {
spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
--
2.11.0
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