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hugetlb: simplify hugetlb handling in follow_page_mask

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During discussions of this series [1], it was suggested that hugetlb
handling code in follow_page_mask could be simplified.  At the beginning
of follow_page_mask, there currently is a call to follow_huge_addr which
'may' handle hugetlb pages.  ia64 is the only architecture which provides
a follow_huge_addr routine that does not return error.  Instead, at each
level of the page table a check is made for a hugetlb entry.  If a hugetlb
entry is found, a call to a routine associated with that entry is made.

Currently, there are two checks for hugetlb entries at each page table
level.  The first check is of the form:

        if (p?d_huge())
                page = follow_huge_p?d();

the second check is of the form:

        if (is_hugepd())
                page = follow_huge_pd().

We can replace these checks, as well as the special handling routines such
as follow_huge_p?d() and follow_huge_pd() with a single routine to handle
hugetlb vmas.

A new routine hugetlb_follow_page_mask is called for hugetlb vmas at the
beginning of follow_page_mask.  hugetlb_follow_page_mask will use the
existing routine huge_pte_offset to walk page tables looking for hugetlb
entries.  huge_pte_offset can be overwritten by architectures, and already
handles special cases such as hugepd entries.

[1] https://lore.kernel.org/linux-mm/cover.1661240170.git.baolin.wang@linux.alibaba.com/

[mike.kravetz@oracle.com: remove vma (pmd sharing) per Peter]
  Link: https://lkml.kernel.org/r/20221028181108.119432-1-mike.kravetz@oracle.com
[mike.kravetz@oracle.com: remove left over hugetlb_vma_unlock_read()]
  Link: https://lkml.kernel.org/r/20221030225825.40872-1-mike.kravetz@oracle.com
Link: https://lkml.kernel.org/r/20220919021348.22151-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Mike Kravetz 2022-09-18 19:13:48 -07:00 committed by Andrew Morton
parent f0c4d9fc9c
commit 57a196a584
5 changed files with 76 additions and 278 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

15
arch/ia64/mm/hugetlbpage.c
View file

@ -91,21 +91,6 @@ int prepare_hugepage_range(struct file *file,
return 0;
}
struct page *follow_huge_addr(struct mm_struct *mm, unsigned long addr, int write)
{
struct page *page;
pte_t *ptep;
if (REGION_NUMBER(addr) != RGN_HPAGE)
return ERR_PTR(-EINVAL);
ptep = huge_pte_offset(mm, addr, HPAGE_SIZE);
if (!ptep || pte_none(*ptep))
return NULL;
page = pte_page(*ptep);
page += ((addr & ~HPAGE_MASK) >> PAGE_SHIFT);
return page;
}
int pmd_huge(pmd_t pmd)
{
return 0;

37
arch/powerpc/mm/hugetlbpage.c
View file

@ -506,43 +506,6 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb,
} while (addr = next, addr != end);
}
struct page *follow_huge_pd(struct vm_area_struct *vma,
unsigned long address, hugepd_t hpd,
int flags, int pdshift)
{
pte_t *ptep;
spinlock_t *ptl;
struct page *page = NULL;
unsigned long mask;
int shift = hugepd_shift(hpd);
struct mm_struct *mm = vma->vm_mm;
retry:
/*
* hugepage directory entries are protected by mm->page_table_lock
* Use this instead of huge_pte_lockptr
*/
ptl = &mm->page_table_lock;
spin_lock(ptl);
ptep = hugepte_offset(hpd, address, pdshift);
if (pte_present(*ptep)) {
mask = (1UL << shift) - 1;
page = pte_page(*ptep);
page += ((address & mask) >> PAGE_SHIFT);
if (flags & FOLL_GET)
get_page(page);
} else {
if (is_hugetlb_entry_migration(*ptep)) {
spin_unlock(ptl);
__migration_entry_wait(mm, ptep, ptl);
goto retry;
}
}
spin_unlock(ptl);
return page;
}
bool __init arch_hugetlb_valid_size(unsigned long size)
{
int shift = __ffs(size);

50
include/linux/hugetlb.h
View file

@ -149,6 +149,8 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
unsigned long len);
int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *,
struct vm_area_struct *, struct vm_area_struct *);
struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags);
long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
struct page **, struct vm_area_struct **,
unsigned long *, unsigned long *, long, unsigned int,
@ -209,17 +211,6 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep);
void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end);
struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
int write);
struct page *follow_huge_pd(struct vm_area_struct *vma,
unsigned long address, hugepd_t hpd,
int flags, int pdshift);
struct page *follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address,
int flags);
struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int flags);
struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
pgd_t *pgd, int flags);
void hugetlb_vma_lock_read(struct vm_area_struct *vma);
void hugetlb_vma_unlock_read(struct vm_area_struct *vma);
@ -272,6 +263,12 @@ static inline void adjust_range_if_pmd_sharing_possible(
{
}
static inline struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags)
{
BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/
}
static inline long follow_hugetlb_page(struct mm_struct *mm,
struct vm_area_struct *vma, struct page **pages,
struct vm_area_struct **vmas, unsigned long *position,
@ -282,12 +279,6 @@ static inline long follow_hugetlb_page(struct mm_struct *mm,
return 0;
}
static inline struct page *follow_huge_addr(struct mm_struct *mm,
unsigned long address, int write)
{
return ERR_PTR(-EINVAL);
}
static inline int copy_hugetlb_page_range(struct mm_struct *dst,
struct mm_struct *src,
struct vm_area_struct *dst_vma,
@ -320,31 +311,6 @@ static inline void hugetlb_show_meminfo_node(int nid)
{
}
static inline struct page *follow_huge_pd(struct vm_area_struct *vma,
unsigned long address, hugepd_t hpd, int flags,
int pdshift)
{
return NULL;
}
static inline struct page *follow_huge_pmd_pte(struct vm_area_struct *vma,
unsigned long address, int flags)
{
return NULL;
}
static inline struct page *follow_huge_pud(struct mm_struct *mm,
unsigned long address, pud_t *pud, int flags)
{
return NULL;
}
static inline struct page *follow_huge_pgd(struct mm_struct *mm,
unsigned long address, pgd_t *pgd, int flags)
{
return NULL;
}
static inline int prepare_hugepage_range(struct file *file,
unsigned long addr, unsigned long len)
{

80
mm/gup.c
View file

@ -537,18 +537,6 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
(FOLL_PIN | FOLL_GET)))
return ERR_PTR(-EINVAL);
/*
* Considering PTE level hugetlb, like continuous-PTE hugetlb on
* ARM64 architecture.
*/
if (is_vm_hugetlb_page(vma)) {
page = follow_huge_pmd_pte(vma, address, flags);
if (page)
return page;
return no_page_table(vma, flags);
}
retry:
if (unlikely(pmd_bad(*pmd)))
return no_page_table(vma, flags);
@ -680,20 +668,6 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
pmdval = READ_ONCE(*pmd);
if (pmd_none(pmdval))
return no_page_table(vma, flags);
if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) {
page = follow_huge_pmd_pte(vma, address, flags);
if (page)
return page;
return no_page_table(vma, flags);
}
if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
page = follow_huge_pd(vma, address,
__hugepd(pmd_val(pmdval)), flags,
PMD_SHIFT);
if (page)
return page;
return no_page_table(vma, flags);
}
retry:
if (!pmd_present(pmdval)) {
/*
@ -783,20 +757,6 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
pud = pud_offset(p4dp, address);
if (pud_none(*pud))
return no_page_table(vma, flags);
if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) {
page = follow_huge_pud(mm, address, pud, flags);
if (page)
return page;
return no_page_table(vma, flags);
}
if (is_hugepd(__hugepd(pud_val(*pud)))) {
page = follow_huge_pd(vma, address,
__hugepd(pud_val(*pud)), flags,
PUD_SHIFT);
if (page)
return page;
return no_page_table(vma, flags);
}
if (pud_devmap(*pud)) {
ptl = pud_lock(mm, pud);
page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
@ -816,7 +776,6 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
struct follow_page_context *ctx)
{
p4d_t *p4d;
struct page *page;
p4d = p4d_offset(pgdp, address);
if (p4d_none(*p4d))
@ -825,14 +784,6 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
if (unlikely(p4d_bad(*p4d)))
return no_page_table(vma, flags);
if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
page = follow_huge_pd(vma, address,
__hugepd(p4d_val(*p4d)), flags,
P4D_SHIFT);
if (page)
return page;
return no_page_table(vma, flags);
}
return follow_pud_mask(vma, address, p4d, flags, ctx);
}
@ -870,10 +821,18 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
ctx->page_mask = 0;
/* make this handle hugepd */
page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
if (!IS_ERR(page)) {
WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN));
/*
* Call hugetlb_follow_page_mask for hugetlb vmas as it will use
* special hugetlb page table walking code. This eliminates the
* need to check for hugetlb entries in the general walking code.
*
* hugetlb_follow_page_mask is only for follow_page() handling here.
* Ordinary GUP uses follow_hugetlb_page for hugetlb processing.
*/
if (is_vm_hugetlb_page(vma)) {
page = hugetlb_follow_page_mask(vma, address, flags);
if (!page)
page = no_page_table(vma, flags);
return page;
}
@ -882,21 +841,6 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
return no_page_table(vma, flags);
if (pgd_huge(*pgd)) {
page = follow_huge_pgd(mm, address, pgd, flags);
if (page)
return page;
return no_page_table(vma, flags);
}
if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
page = follow_huge_pd(vma, address,
__hugepd(pgd_val(*pgd)), flags,
PGDIR_SHIFT);
if (page)
return page;
return no_page_table(vma, flags);
}
return follow_p4d_mask(vma, address, pgd, flags, ctx);
}

172
mm/hugetlb.c
View file

@ -6209,6 +6209,62 @@ static inline bool __follow_hugetlb_must_fault(unsigned int flags, pte_t *pte,
return false;
}
struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags)
{
struct hstate *h = hstate_vma(vma);
struct mm_struct *mm = vma->vm_mm;
unsigned long haddr = address & huge_page_mask(h);
struct page *page = NULL;
spinlock_t *ptl;
pte_t *pte, entry;
/*
* FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via
* follow_hugetlb_page().
*/
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
retry:
pte = huge_pte_offset(mm, haddr, huge_page_size(h));
if (!pte)
return NULL;
ptl = huge_pte_lock(h, mm, pte);
entry = huge_ptep_get(pte);
if (pte_present(entry)) {
page = pte_page(entry) +
((address & ~huge_page_mask(h)) >> PAGE_SHIFT);
/*
* Note that page may be a sub-page, and with vmemmap
* optimizations the page struct may be read only.
* try_grab_page() will increase the ref count on the
* head page, so this will be OK.
*
* try_grab_page() should always succeed here, because we hold
* the ptl lock and have verified pte_present().
*/
if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
page = NULL;
goto out;
}
} else {
if (is_hugetlb_entry_migration(entry)) {
spin_unlock(ptl);
__migration_entry_wait_huge(pte, ptl);
goto retry;
}
/*
* hwpoisoned entry is treated as no_page_table in
* follow_page_mask().
*/
}
out:
spin_unlock(ptl);
return page;
}
long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page **pages, struct vm_area_struct **vmas,
unsigned long *position, unsigned long *nr_pages,
@ -7201,122 +7257,6 @@ __weak unsigned long hugetlb_mask_last_page(struct hstate *h)
* These functions are overwritable if your architecture needs its own
* behavior.
*/
struct page * __weak
follow_huge_addr(struct mm_struct *mm, unsigned long address,
int write)
{
return ERR_PTR(-EINVAL);
}
struct page * __weak
follow_huge_pd(struct vm_area_struct *vma,
unsigned long address, hugepd_t hpd, int flags, int pdshift)
{
WARN(1, "hugepd follow called with no support for hugepage directory format\n");
return NULL;
}
struct page * __weak
follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address, int flags)
{
struct hstate *h = hstate_vma(vma);
struct mm_struct *mm = vma->vm_mm;
struct page *page = NULL;
spinlock_t *ptl;
pte_t *ptep, pte;
/*
* FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via
* follow_hugetlb_page().
*/
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
retry:
ptep = huge_pte_offset(mm, address, huge_page_size(h));
if (!ptep)
return NULL;
ptl = huge_pte_lock(h, mm, ptep);
pte = huge_ptep_get(ptep);
if (pte_present(pte)) {
page = pte_page(pte) +
((address & ~huge_page_mask(h)) >> PAGE_SHIFT);
/*
* try_grab_page() should always succeed here, because: a) we
* hold the pmd (ptl) lock, and b) we've just checked that the
* huge pmd (head) page is present in the page tables. The ptl
* prevents the head page and tail pages from being rearranged
* in any way. So this page must be available at this point,
* unless the page refcount overflowed:
*/
if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
page = NULL;
goto out;
}
} else {
if (is_hugetlb_entry_migration(pte)) {
spin_unlock(ptl);
__migration_entry_wait_huge(ptep, ptl);
goto retry;
}
/*
* hwpoisoned entry is treated as no_page_table in
* follow_page_mask().
*/
}
out:
spin_unlock(ptl);
return page;
}
struct page * __weak
follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int flags)
{
struct page *page = NULL;
spinlock_t *ptl;
pte_t pte;
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
retry:
ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud);
if (!pud_huge(*pud))
goto out;
pte = huge_ptep_get((pte_t *)pud);
if (pte_present(pte)) {
page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
page = NULL;
goto out;
}
} else {
if (is_hugetlb_entry_migration(pte)) {
spin_unlock(ptl);
__migration_entry_wait(mm, (pte_t *)pud, ptl);
goto retry;
}
/*
* hwpoisoned entry is treated as no_page_table in
* follow_page_mask().
*/
}
out:
spin_unlock(ptl);
return page;
}
struct page * __weak
follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int flags)
{
if (flags & (FOLL_GET | FOLL_PIN))
return NULL;
return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);
}
int isolate_hugetlb(struct page *page, struct list_head *list)
{
int ret = 0;