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android / kernel / common / 864f2d3482f4b / . / mm / gup.c
blob: 1a23cd0b4fba1223c25d012c2cc00c90b0961219 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/memremap.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/secretmem.h>
#include <linux/sched/signal.h>
#include <linux/rwsem.h>
#include <linux/hugetlb.h>
#include <linux/migrate.h>
#include <linux/mm_inline.h>
#include <linux/sched/mm.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include "internal.h"
struct follow_page_context {
struct dev_pagemap *pgmap;
unsigned int page_mask;
};
static void hpage_pincount_add(struct page *page, int refs)
{
VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
VM_BUG_ON_PAGE(page != compound_head(page), page);
atomic_add(refs, compound_pincount_ptr(page));
}
static void hpage_pincount_sub(struct page *page, int refs)
{
VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
VM_BUG_ON_PAGE(page != compound_head(page), page);
atomic_sub(refs, compound_pincount_ptr(page));
}
/* Equivalent to calling put_page() @refs times. */
static void put_page_refs(struct page *page, int refs)
{
#ifdef CONFIG_DEBUG_VM
if (VM_WARN_ON_ONCE_PAGE(page_ref_count(page) < refs, page))
return;
#endif
/*
* Calling put_page() for each ref is unnecessarily slow. Only the last
* ref needs a put_page().
*/
if (refs > 1)
page_ref_sub(page, refs - 1);
put_page(page);
}
/*
* Return the compound head page with ref appropriately incremented,
* or NULL if that failed.
*/
static inline struct page *try_get_compound_head(struct page *page, int refs)
{
struct page *head = compound_head(page);
if (WARN_ON_ONCE(page_ref_count(head) < 0))
return NULL;
if (unlikely(!page_cache_add_speculative(head, refs)))
return NULL;
/*
* At this point we have a stable reference to the head page; but it
* could be that between the compound_head() lookup and the refcount
* increment, the compound page was split, in which case we'd end up
* holding a reference on a page that has nothing to do with the page
* we were given anymore.
* So now that the head page is stable, recheck that the pages still
* belong together.
*/
if (unlikely(compound_head(page) != head)) {
put_page_refs(head, refs);
return NULL;
}
return head;
}
/**
* try_grab_compound_head() - attempt to elevate a page's refcount, by a
* flags-dependent amount.
*
* Even though the name includes "compound_head", this function is still
* appropriate for callers that have a non-compound @page to get.
*
* @page: pointer to page to be grabbed
* @refs: the value to (effectively) add to the page's refcount
* @flags: gup flags: these are the FOLL_* flag values.
*
* "grab" names in this file mean, "look at flags to decide whether to use
* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
*
* Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
* same time. (That's true throughout the get_user_pages*() and
* pin_user_pages*() APIs.) Cases:
*
* FOLL_GET: page's refcount will be incremented by @refs.
*
* FOLL_PIN on compound pages that are > two pages long: page's refcount will
* be incremented by @refs, and page[2].hpage_pinned_refcount will be
* incremented by @refs * GUP_PIN_COUNTING_BIAS.
*
* FOLL_PIN on normal pages, or compound pages that are two pages long:
* page's refcount will be incremented by @refs * GUP_PIN_COUNTING_BIAS.
*
* Return: head page (with refcount appropriately incremented) for success, or
* NULL upon failure. If neither FOLL_GET nor FOLL_PIN was set, that's
* considered failure, and furthermore, a likely bug in the caller, so a warning
* is also emitted.
*/
__maybe_unused struct page *try_grab_compound_head(struct page *page,
int refs, unsigned int flags)
{
if (flags & FOLL_GET)
return try_get_compound_head(page, refs);
else if (flags & FOLL_PIN) {
/*
* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
* right zone, so fail and let the caller fall back to the slow
* path.
*/
if (unlikely((flags & FOLL_LONGTERM) &&
!is_pinnable_page(page)))
return NULL;
/*
* CAUTION: Don't use compound_head() on the page before this
* point, the result won't be stable.
*/
page = try_get_compound_head(page, refs);
if (!page)
return NULL;
/*
* When pinning a compound page of order > 1 (which is what
* hpage_pincount_available() checks for), use an exact count to
* track it, via hpage_pincount_add/_sub().
*
* However, be sure to *also* increment the normal page refcount
* field at least once, so that the page really is pinned.
* That's why the refcount from the earlier
* try_get_compound_head() is left intact.
*/
if (hpage_pincount_available(page))
hpage_pincount_add(page, refs);
else
page_ref_add(page, refs * (GUP_PIN_COUNTING_BIAS - 1));
mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED,
refs);
return page;
}
WARN_ON_ONCE(1);
return NULL;
}
static void put_compound_head(struct page *page, int refs, unsigned int flags)
{
if (flags & FOLL_PIN) {
mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
refs);
if (hpage_pincount_available(page))
hpage_pincount_sub(page, refs);
else
refs *= GUP_PIN_COUNTING_BIAS;
}
put_page_refs(page, refs);
}
/**
* try_grab_page() - elevate a page's refcount by a flag-dependent amount
*
* This might not do anything at all, depending on the flags argument.
*
* "grab" names in this file mean, "look at flags to decide whether to use
* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
*
* @page: pointer to page to be grabbed
* @flags: gup flags: these are the FOLL_* flag values.
*
* Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
* time. Cases: please see the try_grab_compound_head() documentation, with
* "refs=1".
*
* Return: true for success, or if no action was required (if neither FOLL_PIN
* nor FOLL_GET was set, nothing is done). False for failure: FOLL_GET or
* FOLL_PIN was set, but the page could not be grabbed.
*/
bool __must_check try_grab_page(struct page *page, unsigned int flags)
{
WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN));
if (flags & FOLL_GET)
return try_get_page(page);
else if (flags & FOLL_PIN) {
int refs = 1;
page = compound_head(page);
if (WARN_ON_ONCE(page_ref_count(page) <= 0))
return false;
if (hpage_pincount_available(page))
hpage_pincount_add(page, 1);
else
refs = GUP_PIN_COUNTING_BIAS;
/*
* Similar to try_grab_compound_head(): even if using the
* hpage_pincount_add/_sub() routines, be sure to
* *also* increment the normal page refcount field at least
* once, so that the page really is pinned.
*/
page_ref_add(page, refs);
mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
}
return true;
}
/**
* unpin_user_page() - release a dma-pinned page
* @page: pointer to page to be released
*
* Pages that were pinned via pin_user_pages*() must be released via either
* unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
* that such pages can be separately tracked and uniquely handled. In
* particular, interactions with RDMA and filesystems need special handling.
*/
void unpin_user_page(struct page *page)
{
put_compound_head(compound_head(page), 1, FOLL_PIN);
}
EXPORT_SYMBOL(unpin_user_page);
static inline void compound_range_next(unsigned long i, unsigned long npages,
struct page **list, struct page **head,
unsigned int *ntails)
{
struct page *next, *page;
unsigned int nr = 1;
if (i >= npages)
return;
next = *list + i;
page = compound_head(next);
if (PageCompound(page) && compound_order(page) >= 1)
nr = min_t(unsigned int,
page + compound_nr(page) - next, npages - i);
*head = page;
*ntails = nr;
}
#define for_each_compound_range(__i, __list, __npages, __head, __ntails) \
for (__i = 0, \
compound_range_next(__i, __npages, __list, &(__head), &(__ntails)); \
__i < __npages; __i += __ntails, \
compound_range_next(__i, __npages, __list, &(__head), &(__ntails)))
static inline void compound_next(unsigned long i, unsigned long npages,
struct page **list, struct page **head,
unsigned int *ntails)
{
struct page *page;
unsigned int nr;
if (i >= npages)
return;
page = compound_head(list[i]);
for (nr = i + 1; nr < npages; nr++) {
if (compound_head(list[nr]) != page)
break;
}
*head = page;
*ntails = nr - i;
}
#define for_each_compound_head(__i, __list, __npages, __head, __ntails) \
for (__i = 0, \
compound_next(__i, __npages, __list, &(__head), &(__ntails)); \
__i < __npages; __i += __ntails, \
compound_next(__i, __npages, __list, &(__head), &(__ntails)))
/**
* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
* @pages: array of pages to be maybe marked dirty, and definitely released.
* @npages: number of pages in the @pages array.
* @make_dirty: whether to mark the pages dirty
*
* "gup-pinned page" refers to a page that has had one of the get_user_pages()
* variants called on that page.
*
* For each page in the @pages array, make that page (or its head page, if a
* compound page) dirty, if @make_dirty is true, and if the page was previously
* listed as clean. In any case, releases all pages using unpin_user_page(),
* possibly via unpin_user_pages(), for the non-dirty case.
*
* Please see the unpin_user_page() documentation for details.
*
* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
* required, then the caller should a) verify that this is really correct,
* because _lock() is usually required, and b) hand code it:
* set_page_dirty_lock(), unpin_user_page().
*
*/
void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
bool make_dirty)
{
unsigned long index;
struct page *head;
unsigned int ntails;
if (!make_dirty) {
unpin_user_pages(pages, npages);
return;
}
for_each_compound_head(index, pages, npages, head, ntails) {
/*
* Checking PageDirty at this point may race with
* clear_page_dirty_for_io(), but that's OK. Two key
* cases:
*
* 1) This code sees the page as already dirty, so it
* skips the call to set_page_dirty(). That could happen
* because clear_page_dirty_for_io() called
* page_mkclean(), followed by set_page_dirty().
* However, now the page is going to get written back,
* which meets the original intention of setting it
* dirty, so all is well: clear_page_dirty_for_io() goes
* on to call TestClearPageDirty(), and write the page
* back.
*
* 2) This code sees the page as clean, so it calls
* set_page_dirty(). The page stays dirty, despite being
* written back, so it gets written back again in the
* next writeback cycle. This is harmless.
*/
if (!PageDirty(head))
set_page_dirty_lock(head);
put_compound_head(head, ntails, FOLL_PIN);
}
}
EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
/**
* unpin_user_page_range_dirty_lock() - release and optionally dirty
* gup-pinned page range
*
* @page: the starting page of a range maybe marked dirty, and definitely released.
* @npages: number of consecutive pages to release.
* @make_dirty: whether to mark the pages dirty
*
* "gup-pinned page range" refers to a range of pages that has had one of the
* pin_user_pages() variants called on that page.
*
* For the page ranges defined by [page .. page+npages], make that range (or
* its head pages, if a compound page) dirty, if @make_dirty is true, and if the
* page range was previously listed as clean.
*
* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
* required, then the caller should a) verify that this is really correct,
* because _lock() is usually required, and b) hand code it:
* set_page_dirty_lock(), unpin_user_page().
*
*/
void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
bool make_dirty)
{
unsigned long index;
struct page *head;
unsigned int ntails;
for_each_compound_range(index, &page, npages, head, ntails) {
if (make_dirty && !PageDirty(head))
set_page_dirty_lock(head);
put_compound_head(head, ntails, FOLL_PIN);
}
}
EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
/**
* unpin_user_pages() - release an array of gup-pinned pages.
* @pages: array of pages to be marked dirty and released.
* @npages: number of pages in the @pages array.
*
* For each page in the @pages array, release the page using unpin_user_page().
*
* Please see the unpin_user_page() documentation for details.
*/
void unpin_user_pages(struct page **pages, unsigned long npages)
{
unsigned long index;
struct page *head;
unsigned int ntails;
/*
* If this WARN_ON() fires, then the system *might* be leaking pages (by
* leaving them pinned), but probably not. More likely, gup/pup returned
* a hard -ERRNO error to the caller, who erroneously passed it here.
*/
if (WARN_ON(IS_ERR_VALUE(npages)))
return;
for_each_compound_head(index, pages, npages, head, ntails)
put_compound_head(head, ntails, FOLL_PIN);
}
EXPORT_SYMBOL(unpin_user_pages);
/*
* Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
* lifecycle. Avoid setting the bit unless necessary, or it might cause write
* cache bouncing on large SMP machines for concurrent pinned gups.
*/
static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
{
if (!test_bit(MMF_HAS_PINNED, mm_flags))
set_bit(MMF_HAS_PINNED, mm_flags);
}
#ifdef CONFIG_MMU
static struct page *no_page_table(struct vm_area_struct *vma,
unsigned int flags)
{
/*
* When core dumping an enormous anonymous area that nobody
* has touched so far, we don't want to allocate unnecessary pages or
* page tables. Return error instead of NULL to skip handle_mm_fault,
* then get_dump_page() will return NULL to leave a hole in the dump.
* But we can only make this optimization where a hole would surely
* be zero-filled if handle_mm_fault() actually did handle it.
*/
if ((flags & FOLL_DUMP) &&
(vma_is_anonymous(vma) || !vma->vm_ops->fault))
return ERR_PTR(-EFAULT);
return NULL;
}
static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
pte_t *pte, unsigned int flags)
{
/* No page to get reference */
if (flags & (FOLL_GET | FOLL_PIN))
return -EFAULT;
if (flags & FOLL_TOUCH) {
pte_t entry = *pte;
if (flags & FOLL_WRITE)
entry = pte_mkdirty(entry);
entry = pte_mkyoung(entry);
if (!pte_same(*pte, entry)) {
set_pte_at(vma->vm_mm, address, pte, entry);
update_mmu_cache(vma, address, pte);
}
}
/* Proper page table entry exists, but no corresponding struct page */
return -EEXIST;
}
/*
* FOLL_FORCE can write to even unwritable pte's, but only
* after we've gone through a COW cycle and they are dirty.
*/
static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
{
return pte_write(pte) ||
((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
}
static struct page *follow_page_pte(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd, unsigned int flags,
struct dev_pagemap **pgmap)
{
struct mm_struct *mm = vma->vm_mm;
struct page *page;
spinlock_t *ptl;
pte_t *ptep, pte;
int ret;
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
(FOLL_PIN | FOLL_GET)))
return ERR_PTR(-EINVAL);
retry:
if (unlikely(pmd_bad(*pmd)))
return no_page_table(vma, flags);
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
pte = *ptep;
if (!pte_present(pte)) {
swp_entry_t entry;
/*
* KSM's break_ksm() relies upon recognizing a ksm page
* even while it is being migrated, so for that case we
* need migration_entry_wait().
*/
if (likely(!(flags & FOLL_MIGRATION)))
goto no_page;
if (pte_none(pte))
goto no_page;
entry = pte_to_swp_entry(pte);
if (!is_migration_entry(entry))
goto no_page;
pte_unmap_unlock(ptep, ptl);
migration_entry_wait(mm, pmd, address);
goto retry;
}
if ((flags & FOLL_NUMA) && pte_protnone(pte))
goto no_page;
if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
pte_unmap_unlock(ptep, ptl);
return NULL;
}
page = vm_normal_page(vma, address, pte);
if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
/*
* Only return device mapping pages in the FOLL_GET or FOLL_PIN
* case since they are only valid while holding the pgmap
* reference.
*/
*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
if (*pgmap)
page = pte_page(pte);
else
goto no_page;
} else if (unlikely(!page)) {
if (flags & FOLL_DUMP) {
/* Avoid special (like zero) pages in core dumps */
page = ERR_PTR(-EFAULT);
goto out;
}
if (is_zero_pfn(pte_pfn(pte))) {
page = pte_page(pte);
} else {
ret = follow_pfn_pte(vma, address, ptep, flags);
page = ERR_PTR(ret);
goto out;
}
}
/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
if (unlikely(!try_grab_page(page, flags))) {
page = ERR_PTR(-ENOMEM);
goto out;
}
/*
* We need to make the page accessible if and only if we are going
* to access its content (the FOLL_PIN case). Please see
* Documentation/core-api/pin_user_pages.rst for details.
*/
if (flags & FOLL_PIN) {
ret = arch_make_page_accessible(page);
if (ret) {
unpin_user_page(page);
page = ERR_PTR(ret);
goto out;
}
}
if (flags & FOLL_TOUCH) {
if ((flags & FOLL_WRITE) &&
!pte_dirty(pte) && !PageDirty(page))
set_page_dirty(page);
/*
* pte_mkyoung() would be more correct here, but atomic care
* is needed to avoid losing the dirty bit: it is easier to use
* mark_page_accessed().
*/
mark_page_accessed(page);
}
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
/* Do not mlock pte-mapped THP */
if (PageTransCompound(page))
goto out;
/*
* The preliminary mapping check is mainly to avoid the
* pointless overhead of lock_page on the ZERO_PAGE
* which might bounce very badly if there is contention.
*
* If the page is already locked, we don't need to
* handle it now - vmscan will handle it later if and
* when it attempts to reclaim the page.
*/
if (page->mapping && trylock_page(page)) {
lru_add_drain(); /* push cached pages to LRU */
/*
* Because we lock page here, and migration is
* blocked by the pte's page reference, and we
* know the page is still mapped, we don't even
* need to check for file-cache page truncation.
*/
mlock_vma_page(page);
unlock_page(page);
}
}
out:
pte_unmap_unlock(ptep, ptl);
return page;
no_page:
pte_unmap_unlock(ptep, ptl);
if (!pte_none(pte))
return NULL;
return no_page_table(vma, flags);
}
static struct page *follow_pmd_mask(struct vm_area_struct *vma,
unsigned long address, pud_t *pudp,
unsigned int flags,
struct follow_page_context *ctx)
{
pmd_t *pmd, pmdval;
spinlock_t *ptl;
struct page *page;
struct mm_struct *mm = vma->vm_mm;
pmd = pmd_offset(pudp, address);
/*
* The READ_ONCE() will stabilize the pmdval in a register or
* on the stack so that it will stop changing under the code.
*/
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(mm, address, pmd, 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)) {
if (likely(!(flags & FOLL_MIGRATION)))
return no_page_table(vma, flags);
VM_BUG_ON(thp_migration_supported() &&
!is_pmd_migration_entry(pmdval));
if (is_pmd_migration_entry(pmdval))
pmd_migration_entry_wait(mm, pmd);
pmdval = READ_ONCE(*pmd);
/*
* MADV_DONTNEED may convert the pmd to null because
* mmap_lock is held in read mode
*/
if (pmd_none(pmdval))
return no_page_table(vma, flags);
goto retry;
}
if (pmd_devmap(pmdval)) {
ptl = pmd_lock(mm, pmd);
page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
spin_unlock(ptl);
if (page)
return page;
}
if (likely(!pmd_trans_huge(pmdval)))
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
return no_page_table(vma, flags);
retry_locked:
ptl = pmd_lock(mm, pmd);
if (unlikely(pmd_none(*pmd))) {
spin_unlock(ptl);
return no_page_table(vma, flags);
}
if (unlikely(!pmd_present(*pmd))) {
spin_unlock(ptl);
if (likely(!(flags & FOLL_MIGRATION)))
return no_page_table(vma, flags);
pmd_migration_entry_wait(mm, pmd);
goto retry_locked;
}
if (unlikely(!pmd_trans_huge(*pmd))) {
spin_unlock(ptl);
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
if (flags & FOLL_SPLIT_PMD) {
int ret;
page = pmd_page(*pmd);
if (is_huge_zero_page(page)) {
spin_unlock(ptl);
ret = 0;
split_huge_pmd(vma, pmd, address);
if (pmd_trans_unstable(pmd))
ret = -EBUSY;
} else {
spin_unlock(ptl);
split_huge_pmd(vma, pmd, address);
ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
}
return ret ? ERR_PTR(ret) :
follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
page = follow_trans_huge_pmd(vma, address, pmd, flags);
spin_unlock(ptl);
ctx->page_mask = HPAGE_PMD_NR - 1;
return page;
}
static struct page *follow_pud_mask(struct vm_area_struct *vma,
unsigned long address, p4d_t *p4dp,
unsigned int flags,
struct follow_page_context *ctx)
{
pud_t *pud;
spinlock_t *ptl;
struct page *page;
struct mm_struct *mm = vma->vm_mm;
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);
spin_unlock(ptl);
if (page)
return page;
}
if (unlikely(pud_bad(*pud)))
return no_page_table(vma, flags);
return follow_pmd_mask(vma, address, pud, flags, ctx);
}
static struct page *follow_p4d_mask(struct vm_area_struct *vma,
unsigned long address, pgd_t *pgdp,
unsigned int flags,
struct follow_page_context *ctx)
{
p4d_t *p4d;
struct page *page;
p4d = p4d_offset(pgdp, address);
if (p4d_none(*p4d))
return no_page_table(vma, flags);
BUILD_BUG_ON(p4d_huge(*p4d));
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);
}
/**
* follow_page_mask - look up a page descriptor from a user-virtual address
* @vma: vm_area_struct mapping @address
* @address: virtual address to look up
* @flags: flags modifying lookup behaviour
* @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
* pointer to output page_mask
*
* @flags can have FOLL_ flags set, defined in <linux/mm.h>
*
* When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
* the device's dev_pagemap metadata to avoid repeating expensive lookups.
*
* On output, the @ctx->page_mask is set according to the size of the page.
*
* Return: the mapped (struct page *), %NULL if no mapping exists, or
* an error pointer if there is a mapping to something not represented
* by a page descriptor (see also vm_normal_page()).
*/
static struct page *follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags,
struct follow_page_context *ctx)
{
pgd_t *pgd;
struct page *page;
struct mm_struct *mm = vma->vm_mm;
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));
return page;
}
pgd = pgd_offset(mm, address);
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);
}
struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
unsigned int foll_flags)
{
struct follow_page_context ctx = { NULL };
struct page *page;
if (vma_is_secretmem(vma))
return NULL;
page = follow_page_mask(vma, address, foll_flags, &ctx);
if (ctx.pgmap)
put_dev_pagemap(ctx.pgmap);
return page;
}
static int get_gate_page(struct mm_struct *mm, unsigned long address,
unsigned int gup_flags, struct vm_area_struct **vma,
struct page **page)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
int ret = -EFAULT;
/* user gate pages are read-only */
if (gup_flags & FOLL_WRITE)
return -EFAULT;
if (address > TASK_SIZE)
pgd = pgd_offset_k(address);
else
pgd = pgd_offset_gate(mm, address);
if (pgd_none(*pgd))
return -EFAULT;
p4d = p4d_offset(pgd, address);
if (p4d_none(*p4d))
return -EFAULT;
pud = pud_offset(p4d, address);
if (pud_none(*pud))
return -EFAULT;
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
return -EFAULT;
VM_BUG_ON(pmd_trans_huge(*pmd));
pte = pte_offset_map(pmd, address);
if (pte_none(*pte))
goto unmap;
*vma = get_gate_vma(mm);
if (!page)
goto out;
*page = vm_normal_page(*vma, address, *pte);
if (!*page) {
if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
goto unmap;
*page = pte_page(*pte);
}
if (unlikely(!try_grab_page(*page, gup_flags))) {
ret = -ENOMEM;
goto unmap;
}
out:
ret = 0;
unmap:
pte_unmap(pte);
return ret;
}
/*
* mmap_lock must be held on entry. If @locked != NULL and *@flags
* does not include FOLL_NOWAIT, the mmap_lock may be released. If it
* is, *@locked will be set to 0 and -EBUSY returned.
*/
static int faultin_page(struct vm_area_struct *vma,
unsigned long address, unsigned int *flags, int *locked)
{
unsigned int fault_flags = 0;
vm_fault_t ret;
/* mlock all present pages, but do not fault in new pages */
if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
return -ENOENT;
if (*flags & FOLL_NOFAULT)
return -EFAULT;
if (*flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
if (*flags & FOLL_REMOTE)
fault_flags |= FAULT_FLAG_REMOTE;
if (locked)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
if (*flags & FOLL_NOWAIT)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
if (*flags & FOLL_TRIED) {
/*
* Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
* can co-exist
*/
fault_flags |= FAULT_FLAG_TRIED;
}
ret = handle_mm_fault(vma, address, fault_flags, NULL);
if (ret & VM_FAULT_ERROR) {
int err = vm_fault_to_errno(ret, *flags);
if (err)
return err;
BUG();
}
if (ret & VM_FAULT_RETRY) {
if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
*locked = 0;
return -EBUSY;
}
/*
* The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
* necessary, even if maybe_mkwrite decided not to set pte_write. We
* can thus safely do subsequent page lookups as if they were reads.
* But only do so when looping for pte_write is futile: in some cases
* userspace may also be wanting to write to the gotten user page,
* which a read fault here might prevent (a readonly page might get
* reCOWed by userspace write).
*/
if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
*flags |= FOLL_COW;
return 0;
}
static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
{
vm_flags_t vm_flags = vma->vm_flags;
int write = (gup_flags & FOLL_WRITE);
int foreign = (gup_flags & FOLL_REMOTE);
if (vm_flags & (VM_IO | VM_PFNMAP))
return -EFAULT;
if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
return -EFAULT;
if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
return -EOPNOTSUPP;
if (vma_is_secretmem(vma))
return -EFAULT;
if (write) {
if (!(vm_flags & VM_WRITE)) {
if (!(gup_flags & FOLL_FORCE))
return -EFAULT;
/*
* We used to let the write,force case do COW in a
* VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
* set a breakpoint in a read-only mapping of an
* executable, without corrupting the file (yet only
* when that file had been opened for writing!).
* Anon pages in shared mappings are surprising: now
* just reject it.
*/
if (!is_cow_mapping(vm_flags))
return -EFAULT;
}
} else if (!(vm_flags & VM_READ)) {
if (!(gup_flags & FOLL_FORCE))
return -EFAULT;
/*
* Is there actually any vma we can reach here which does not
* have VM_MAYREAD set?
*/
if (!(vm_flags & VM_MAYREAD))
return -EFAULT;
}
/*
* gups are always data accesses, not instruction
* fetches, so execute=false here
*/
if (!arch_vma_access_permitted(vma, write, false, foreign))
return -EFAULT;
return 0;
}
/**
* __get_user_pages() - pin user pages in memory
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @vmas: array of pointers to vmas corresponding to each page.
* Or NULL if the caller does not require them.
* @locked: whether we're still with the mmap_lock held
*
* Returns either number of pages pinned (which may be less than the
* number requested), or an error. Details about the return value:
*
* -- If nr_pages is 0, returns 0.
* -- If nr_pages is >0, but no pages were pinned, returns -errno.
* -- If nr_pages is >0, and some pages were pinned, returns the number of
* pages pinned. Again, this may be less than nr_pages.
* -- 0 return value is possible when the fault would need to be retried.
*
* The caller is responsible for releasing returned @pages, via put_page().
*
* @vmas are valid only as long as mmap_lock is held.
*
* Must be called with mmap_lock held. It may be released. See below.
*
* __get_user_pages walks a process's page tables and takes a reference to
* each struct page that each user address corresponds to at a given
* instant. That is, it takes the page that would be accessed if a user
* thread accesses the given user virtual address at that instant.
*
* This does not guarantee that the page exists in the user mappings when
* __get_user_pages returns, and there may even be a completely different
* page there in some cases (eg. if mmapped pagecache has been invalidated
* and subsequently re faulted). However it does guarantee that the page
* won't be freed completely. And mostly callers simply care that the page
* contains data that was valid *at some point in time*. Typically, an IO
* or similar operation cannot guarantee anything stronger anyway because
* locks can't be held over the syscall boundary.
*
* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
* the page is written to, set_page_dirty (or set_page_dirty_lock, as
* appropriate) must be called after the page is finished with, and
* before put_page is called.
*
* If @locked != NULL, *@locked will be set to 0 when mmap_lock is
* released by an up_read(). That can happen if @gup_flags does not
* have FOLL_NOWAIT.
*
* A caller using such a combination of @locked and @gup_flags
* must therefore hold the mmap_lock for reading only, and recognize
* when it's been released. Otherwise, it must be held for either
* reading or writing and will not be released.
*
* In most cases, get_user_pages or get_user_pages_fast should be used
* instead of __get_user_pages. __get_user_pages should be used only if
* you need some special @gup_flags.
*/
static long __get_user_pages(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
long ret = 0, i = 0;
struct vm_area_struct *vma = NULL;
struct follow_page_context ctx = { NULL };
if (!nr_pages)
return 0;
start = untagged_addr(start);
VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
/*
* If FOLL_FORCE is set then do not force a full fault as the hinting
* fault information is unrelated to the reference behaviour of a task
* using the address space
*/
if (!(gup_flags & FOLL_FORCE))
gup_flags |= FOLL_NUMA;
do {
struct page *page;
unsigned int foll_flags = gup_flags;
unsigned int page_increm;
/* first iteration or cross vma bound */
if (!vma || start >= vma->vm_end) {
vma = find_extend_vma(mm, start);
if (!vma && in_gate_area(mm, start)) {
ret = get_gate_page(mm, start & PAGE_MASK,
gup_flags, &vma,
pages ? &pages[i] : NULL);
if (ret)
goto out;
ctx.page_mask = 0;
goto next_page;
}
if (!vma) {
ret = -EFAULT;
goto out;
}
ret = check_vma_flags(vma, gup_flags);
if (ret)
goto out;
if (is_vm_hugetlb_page(vma)) {
i = follow_hugetlb_page(mm, vma, pages, vmas,
&start, &nr_pages, i,
gup_flags, locked);
if (locked && *locked == 0) {
/*
* We've got a VM_FAULT_RETRY
* and we've lost mmap_lock.
* We must stop here.
*/
BUG_ON(gup_flags & FOLL_NOWAIT);
goto out;
}
continue;
}
}
retry:
/*
* If we have a pending SIGKILL, don't keep faulting pages and
* potentially allocating memory.
*/
if (fatal_signal_pending(current)) {
ret = -EINTR;
goto out;
}
cond_resched();
page = follow_page_mask(vma, start, foll_flags, &ctx);
if (!page) {
ret = faultin_page(vma, start, &foll_flags, locked);
switch (ret) {
case 0:
goto retry;
case -EBUSY:
ret = 0;
fallthrough;
case -EFAULT:
case -ENOMEM:
case -EHWPOISON:
goto out;
case -ENOENT:
goto next_page;
}
BUG();
} else if (PTR_ERR(page) == -EEXIST) {
/*
* Proper page table entry exists, but no corresponding
* struct page.
*/
goto next_page;
} else if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
}
if (pages) {
pages[i] = page;
flush_anon_page(vma, page, start);
flush_dcache_page(page);
ctx.page_mask = 0;
}
next_page:
if (vmas) {
vmas[i] = vma;
ctx.page_mask = 0;
}
page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
if (page_increm > nr_pages)
page_increm = nr_pages;
i += page_increm;
start += page_increm * PAGE_SIZE;
nr_pages -= page_increm;
} while (nr_pages);
out:
if (ctx.pgmap)
put_dev_pagemap(ctx.pgmap);
return i ? i : ret;
}
static bool vma_permits_fault(struct vm_area_struct *vma,
unsigned int fault_flags)
{
bool write = !!(fault_flags & FAULT_FLAG_WRITE);
bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
if (!(vm_flags & vma->vm_flags))
return false;
/*
* The architecture might have a hardware protection
* mechanism other than read/write that can deny access.
*
* gup always represents data access, not instruction
* fetches, so execute=false here:
*/
if (!arch_vma_access_permitted(vma, write, false, foreign))
return false;
return true;
}
/**
* fixup_user_fault() - manually resolve a user page fault
* @mm: mm_struct of target mm
* @address: user address
* @fault_flags:flags to pass down to handle_mm_fault()
* @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller
* does not allow retry. If NULL, the caller must guarantee
* that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
*
* This is meant to be called in the specific scenario where for locking reasons
* we try to access user memory in atomic context (within a pagefault_disable()
* section), this returns -EFAULT, and we want to resolve the user fault before
* trying again.
*
* Typically this is meant to be used by the futex code.
*
* The main difference with get_user_pages() is that this function will
* unconditionally call handle_mm_fault() which will in turn perform all the
* necessary SW fixup of the dirty and young bits in the PTE, while
* get_user_pages() only guarantees to update these in the struct page.
*
* This is important for some architectures where those bits also gate the
* access permission to the page because they are maintained in software. On
* such architectures, gup() will not be enough to make a subsequent access
* succeed.
*
* This function will not return with an unlocked mmap_lock. So it has not the
* same semantics wrt the @mm->mmap_lock as does filemap_fault().
*/
int fixup_user_fault(struct mm_struct *mm,
unsigned long address, unsigned int fault_flags,
bool *unlocked)
{
struct vm_area_struct *vma;
vm_fault_t ret;
address = untagged_addr(address);
if (unlocked)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
retry:
vma = find_extend_vma(mm, address);
if (!vma || address < vma->vm_start)
return -EFAULT;
if (!vma_permits_fault(vma, fault_flags))
return -EFAULT;
if ((fault_flags & FAULT_FLAG_KILLABLE) &&
fatal_signal_pending(current))
return -EINTR;
ret = handle_mm_fault(vma, address, fault_flags, NULL);
if (ret & VM_FAULT_ERROR) {
int err = vm_fault_to_errno(ret, 0);
if (err)
return err;
BUG();
}
if (ret & VM_FAULT_RETRY) {
mmap_read_lock(mm);
*unlocked = true;
fault_flags |= FAULT_FLAG_TRIED;
goto retry;
}
return 0;
}
EXPORT_SYMBOL_GPL(fixup_user_fault);
/*
* Please note that this function, unlike __get_user_pages will not
* return 0 for nr_pages > 0 without FOLL_NOWAIT
*/
static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
unsigned long start,
unsigned long nr_pages,
struct page **pages,
struct vm_area_struct **vmas,
int *locked,
unsigned int flags)
{
long ret, pages_done;
bool lock_dropped;
if (locked) {
/* if VM_FAULT_RETRY can be returned, vmas become invalid */
BUG_ON(vmas);
/* check caller initialized locked */
BUG_ON(*locked != 1);
}
if (flags & FOLL_PIN)
mm_set_has_pinned_flag(&mm->flags);
/*
* FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
* is to set FOLL_GET if the caller wants pages[] filled in (but has
* carelessly failed to specify FOLL_GET), so keep doing that, but only
* for FOLL_GET, not for the newer FOLL_PIN.
*
* FOLL_PIN always expects pages to be non-null, but no need to assert
* that here, as any failures will be obvious enough.
*/
if (pages && !(flags & FOLL_PIN))
flags |= FOLL_GET;
pages_done = 0;
lock_dropped = false;
for (;;) {
ret = __get_user_pages(mm, start, nr_pages, flags, pages,
vmas, locked);
if (!locked)
/* VM_FAULT_RETRY couldn't trigger, bypass */
return ret;
/* VM_FAULT_RETRY cannot return errors */
if (!*locked) {
BUG_ON(ret < 0);
BUG_ON(ret >= nr_pages);
}
if (ret > 0) {
nr_pages -= ret;
pages_done += ret;
if (!nr_pages)
break;
}
if (*locked) {
/*
* VM_FAULT_RETRY didn't trigger or it was a
* FOLL_NOWAIT.
*/
if (!pages_done)
pages_done = ret;
break;
}
/*
* VM_FAULT_RETRY triggered, so seek to the faulting offset.
* For the prefault case (!pages) we only update counts.
*/
if (likely(pages))
pages += ret;
start += ret << PAGE_SHIFT;
lock_dropped = true;
retry:
/*
* Repeat on the address that fired VM_FAULT_RETRY
* with both FAULT_FLAG_ALLOW_RETRY and
* FAULT_FLAG_TRIED. Note that GUP can be interrupted
* by fatal signals, so we need to check it before we
* start trying again otherwise it can loop forever.
*/
if (fatal_signal_pending(current)) {
if (!pages_done)
pages_done = -EINTR;
break;
}
ret = mmap_read_lock_killable(mm);
if (ret) {
BUG_ON(ret > 0);
if (!pages_done)
pages_done = ret;
break;
}
*locked = 1;
ret = __get_user_pages(mm, start, 1, flags | FOLL_TRIED,
pages, NULL, locked);
if (!*locked) {
/* Continue to retry until we succeeded */
BUG_ON(ret != 0);
goto retry;
}
if (ret != 1) {
BUG_ON(ret > 1);
if (!pages_done)
pages_done = ret;
break;
}
nr_pages--;
pages_done++;
if (!nr_pages)
break;
if (likely(pages))
pages++;
start += PAGE_SIZE;
}
if (lock_dropped && *locked) {
/*
* We must let the caller know we temporarily dropped the lock
* and so the critical section protected by it was lost.
*/
mmap_read_unlock(mm);
*locked = 0;
}
return pages_done;
}
/**
* populate_vma_page_range() - populate a range of pages in the vma.
* @vma: target vma
* @start: start address
* @end: end address
* @locked: whether the mmap_lock is still held
*
* This takes care of mlocking the pages too if VM_LOCKED is set.
*
* Return either number of pages pinned in the vma, or a negative error
* code on error.
*
* vma->vm_mm->mmap_lock must be held.
*
* If @locked is NULL, it may be held for read or write and will
* be unperturbed.
*
* If @locked is non-NULL, it must held for read only and may be
* released. If it's released, *@locked will be set to 0.
*/
long populate_vma_page_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end, int *locked)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
VM_BUG_ON_VMA(start < vma->vm_start, vma);
VM_BUG_ON_VMA(end > vma->vm_end, vma);
mmap_assert_locked(mm);
gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
if (vma->vm_flags & VM_LOCKONFAULT)
gup_flags &= ~FOLL_POPULATE;
/*
* We want to touch writable mappings with a write fault in order
* to break COW, except for shared mappings because these don't COW
* and we would not want to dirty them for nothing.
*/
if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
gup_flags |= FOLL_WRITE;
/*
* We want mlock to succeed for regions that have any permissions
* other than PROT_NONE.
*/
if (vma_is_accessible(vma))
gup_flags |= FOLL_FORCE;
/*
* We made sure addr is within a VMA, so the following will
* not result in a stack expansion that recurses back here.
*/
return __get_user_pages(mm, start, nr_pages, gup_flags,
NULL, NULL, locked);
}
/*
* faultin_vma_page_range() - populate (prefault) page tables inside the
* given VMA range readable/writable
*
* This takes care of mlocking the pages, too, if VM_LOCKED is set.
*
* @vma: target vma
* @start: start address
* @end: end address
* @write: whether to prefault readable or writable
* @locked: whether the mmap_lock is still held
*
* Returns either number of processed pages in the vma, or a negative error
* code on error (see __get_user_pages()).
*
* vma->vm_mm->mmap_lock must be held. The range must be page-aligned and
* covered by the VMA.
*
* If @locked is NULL, it may be held for read or write and will be unperturbed.
*
* If @locked is non-NULL, it must held for read only and may be released. If
* it's released, *@locked will be set to 0.
*/
long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end, bool write, int *locked)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
VM_BUG_ON_VMA(start < vma->vm_start, vma);
VM_BUG_ON_VMA(end > vma->vm_end, vma);
mmap_assert_locked(mm);
/*
* FOLL_TOUCH: Mark page accessed and thereby young; will also mark
* the page dirty with FOLL_WRITE -- which doesn't make a
* difference with !FOLL_FORCE, because the page is writable
* in the page table.
* FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
* a poisoned page.
* FOLL_POPULATE: Always populate memory with VM_LOCKONFAULT.
* !FOLL_FORCE: Require proper access permissions.
*/
gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK | FOLL_HWPOISON;
if (write)
gup_flags |= FOLL_WRITE;
/*
* We want to report -EINVAL instead of -EFAULT for any permission
* problems or incompatible mappings.
*/
if (check_vma_flags(vma, gup_flags))
return -EINVAL;
return __get_user_pages(mm, start, nr_pages, gup_flags,
NULL, NULL, locked);
}
/*
* __mm_populate - populate and/or mlock pages within a range of address space.
*
* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
* flags. VMAs must be already marked with the desired vm_flags, and
* mmap_lock must not be held.
*/
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
{
struct mm_struct *mm = current->mm;
unsigned long end, nstart, nend;
struct vm_area_struct *vma = NULL;
int locked = 0;
long ret = 0;
end = start + len;
for (nstart = start; nstart < end; nstart = nend) {
/*
* We want to fault in pages for [nstart; end) address range.
* Find first corresponding VMA.
*/
if (!locked) {
locked = 1;
mmap_read_lock(mm);
vma = find_vma(mm, nstart);
} else if (nstart >= vma->vm_end)
vma = vma->vm_next;
if (!vma || vma->vm_start >= end)
break;
/*
* Set [nstart; nend) to intersection of desired address
* range with the first VMA. Also, skip undesirable VMA types.
*/
nend = min(end, vma->vm_end);
if (vma->vm_flags & (VM_IO | VM_PFNMAP))
continue;
if (nstart < vma->vm_start)
nstart = vma->vm_start;
/*
* Now fault in a range of pages. populate_vma_page_range()
* double checks the vma flags, so that it won't mlock pages
* if the vma was already munlocked.
*/
ret = populate_vma_page_range(vma, nstart, nend, &locked);
if (ret < 0) {
if (ignore_errors) {
ret = 0;
continue; /* continue at next VMA */
}
break;
}
nend = nstart + ret * PAGE_SIZE;
ret = 0;
}
if (locked)
mmap_read_unlock(mm);
return ret; /* 0 or negative error code */
}
#else /* CONFIG_MMU */
static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
unsigned long nr_pages, struct page **pages,
struct vm_area_struct **vmas, int *locked,
unsigned int foll_flags)
{
struct vm_area_struct *vma;
unsigned long vm_flags;
long i;
/* calculate required read or write permissions.
* If FOLL_FORCE is set, we only require the "MAY" flags.
*/
vm_flags = (foll_flags & FOLL_WRITE) ?
(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= (foll_flags & FOLL_FORCE) ?
(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
for (i = 0; i < nr_pages; i++) {
vma = find_vma(mm, start);
if (!vma)
goto finish_or_fault;
/* protect what we can, including chardevs */
if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
!(vm_flags & vma->vm_flags))
goto finish_or_fault;
if (pages) {
pages[i] = virt_to_page(start);
if (pages[i])
get_page(pages[i]);
}
if (vmas)
vmas[i] = vma;
start = (start + PAGE_SIZE) & PAGE_MASK;
}
return i;
finish_or_fault:
return i ? : -EFAULT;
}
#endif /* !CONFIG_MMU */
/**
* fault_in_writeable - fault in userspace address range for writing
* @uaddr: start of address range
* @size: size of address range
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*/
size_t fault_in_writeable(char __user *uaddr, size_t size)
{
char __user *start = uaddr, *end;
if (unlikely(size == 0))
return 0;
if (!PAGE_ALIGNED(uaddr)) {
if (unlikely(__put_user(0, uaddr) != 0))
return size;
uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr);
}
end = (char __user *)PAGE_ALIGN((unsigned long)start + size);
if (unlikely(end < start))
end = NULL;
while (uaddr != end) {
if (unlikely(__put_user(0, uaddr) != 0))
goto out;
uaddr += PAGE_SIZE;
}
out:
if (size > uaddr - start)
return size - (uaddr - start);
return 0;
}
EXPORT_SYMBOL(fault_in_writeable);
/*
* fault_in_safe_writeable - fault in an address range for writing
* @uaddr: start of address range
* @size: length of address range
*
* Faults in an address range for writing. This is primarily useful when we
* already know that some or all of the pages in the address range aren't in
* memory.
*
* Unlike fault_in_writeable(), this function is non-destructive.
*
* Note that we don't pin or otherwise hold the pages referenced that we fault
* in. There's no guarantee that they'll stay in memory for any duration of
* time.
*
* Returns the number of bytes not faulted in, like copy_to_user() and
* copy_from_user().
*/
size_t fault_in_safe_writeable(const char __user *uaddr, size_t size)
{
unsigned long start = (unsigned long)uaddr, end;
struct mm_struct *mm = current->mm;
bool unlocked = false;
if (unlikely(size == 0))
return 0;
end = PAGE_ALIGN(start + size);
if (end < start)
end = 0;
mmap_read_lock(mm);
do {
if (fixup_user_fault(mm, start, FAULT_FLAG_WRITE, &unlocked))
break;
start = (start + PAGE_SIZE) & PAGE_MASK;
} while (start != end);
mmap_read_unlock(mm);
if (size > (unsigned long)uaddr - start)
return size - ((unsigned long)uaddr - start);
return 0;
}
EXPORT_SYMBOL(fault_in_safe_writeable);
/**
* fault_in_readable - fault in userspace address range for reading
* @uaddr: start of user address range
* @size: size of user address range
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*/
size_t fault_in_readable(const char __user *uaddr, size_t size)
{
const char __user *start = uaddr, *end;
volatile char c;
if (unlikely(size == 0))
return 0;
if (!PAGE_ALIGNED(uaddr)) {
if (unlikely(__get_user(c, uaddr) != 0))
return size;
uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr);
}
end = (const char __user *)PAGE_ALIGN((unsigned long)start + size);
if (unlikely(end < start))
end = NULL;
while (uaddr != end) {
if (unlikely(__get_user(c, uaddr) != 0))
goto out;
uaddr += PAGE_SIZE;
}
out:
(void)c;
if (size > uaddr - start)
return size - (uaddr - start);
return 0;
}
EXPORT_SYMBOL(fault_in_readable);
/**
* get_dump_page() - pin user page in memory while writing it to core dump
* @addr: user address
*
* Returns struct page pointer of user page pinned for dump,
* to be freed afterwards by put_page().
*
* Returns NULL on any kind of failure - a hole must then be inserted into
* the corefile, to preserve alignment with its headers; and also returns
* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
* allowing a hole to be left in the corefile to save disk space.
*
* Called without mmap_lock (takes and releases the mmap_lock by itself).
*/
#ifdef CONFIG_ELF_CORE
struct page *get_dump_page(unsigned long addr)
{
struct mm_struct *mm = current->mm;
struct page *page;
int locked = 1;
int ret;
if (mmap_read_lock_killable(mm))
return NULL;
ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked,
FOLL_FORCE | FOLL_DUMP | FOLL_GET);
if (locked)
mmap_read_unlock(mm);
return (ret == 1) ? page : NULL;
}
#endif /* CONFIG_ELF_CORE */
#ifdef CONFIG_MIGRATION
/*
* Check whether all pages are pinnable, if so return number of pages. If some
* pages are not pinnable, migrate them, and unpin all pages. Return zero if
* pages were migrated, or if some pages were not successfully isolated.
* Return negative error if migration fails.
*/
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages,
unsigned int gup_flags)
{
unsigned long i;
unsigned long isolation_error_count = 0;
bool drain_allow = true;
LIST_HEAD(movable_page_list);
long ret = 0;
struct page *prev_head = NULL;
struct page *head;
struct migration_target_control mtc = {
.nid = NUMA_NO_NODE,
.gfp_mask = GFP_USER | __GFP_NOWARN,
};
for (i = 0; i < nr_pages; i++) {
head = compound_head(pages[i]);
if (head == prev_head)
continue;
prev_head = head;
/*
* If we get a movable page, since we are going to be pinning
* these entries, try to move them out if possible.
*/
if (!is_pinnable_page(head)) {
if (PageHuge(head)) {
if (!isolate_huge_page(head, &movable_page_list))
isolation_error_count++;
} else {
if (!PageLRU(head) && drain_allow) {
lru_add_drain_all();
drain_allow = false;
}
if (isolate_lru_page(head)) {
isolation_error_count++;
continue;
}
list_add_tail(&head->lru, &movable_page_list);
mod_node_page_state(page_pgdat(head),
NR_ISOLATED_ANON +
page_is_file_lru(head),
thp_nr_pages(head));
}
}
}
/*
* If list is empty, and no isolation errors, means that all pages are
* in the correct zone.
*/
if (list_empty(&movable_page_list) && !isolation_error_count)
return nr_pages;
if (gup_flags & FOLL_PIN) {
unpin_user_pages(pages, nr_pages);
} else {
for (i = 0; i < nr_pages; i++)
put_page(pages[i]);
}
if (!list_empty(&movable_page_list)) {
ret = migrate_pages(&movable_page_list, alloc_migration_target,
NULL, (unsigned long)&mtc, MIGRATE_SYNC,
MR_LONGTERM_PIN, NULL);
if (ret && !list_empty(&movable_page_list))
putback_movable_pages(&movable_page_list);
}
return ret > 0 ? -ENOMEM : ret;
}
#else
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages,
unsigned int gup_flags)
{
return nr_pages;
}
#endif /* CONFIG_MIGRATION */
/*
* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
* allows us to process the FOLL_LONGTERM flag.
*/
static long __gup_longterm_locked(struct mm_struct *mm,
unsigned long start,
unsigned long nr_pages,
struct page **pages,
struct vm_area_struct **vmas,
unsigned int gup_flags)
{
unsigned int flags;
long rc;
if (!(gup_flags & FOLL_LONGTERM))
return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
NULL, gup_flags);
flags = memalloc_pin_save();
do {
rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
NULL, gup_flags);
if (rc <= 0)
break;
rc = check_and_migrate_movable_pages(rc, pages, gup_flags);
} while (!rc);
memalloc_pin_restore(flags);
return rc;
}
static bool is_valid_gup_flags(unsigned int gup_flags)
{
/*
* FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
* never directly by the caller, so enforce that with an assertion:
*/
if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
return false;
/*
* FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying
* that is, FOLL_LONGTERM is a specific case, more restrictive case of
* FOLL_PIN.
*/
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
return false;
return true;
}
#ifdef CONFIG_MMU
static long __get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
/*
* Parts of FOLL_LONGTERM behavior are incompatible with
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
* vmas. However, this only comes up if locked is set, and there are
* callers that do request FOLL_LONGTERM, but do not set locked. So,
* allow what we can.
*/
if (gup_flags & FOLL_LONGTERM) {
if (WARN_ON_ONCE(locked))
return -EINVAL;
/*
* This will check the vmas (even if our vmas arg is NULL)
* and return -ENOTSUPP if DAX isn't allowed in this case:
*/
return __gup_longterm_locked(mm, start, nr_pages, pages,
vmas, gup_flags | FOLL_TOUCH |
FOLL_REMOTE);
}
return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
locked,
gup_flags | FOLL_TOUCH | FOLL_REMOTE);
}
/**
* get_user_pages_remote() - pin user pages in memory
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @vmas: array of pointers to vmas corresponding to each page.
* Or NULL if the caller does not require them.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
*
* Returns either number of pages pinned (which may be less than the
* number requested), or an error. Details about the return value:
*
* -- If nr_pages is 0, returns 0.
* -- If nr_pages is >0, but no pages were pinned, returns -errno.
* -- If nr_pages is >0, and some pages were pinned, returns the number of
* pages pinned. Again, this may be less than nr_pages.
*
* The caller is responsible for releasing returned @pages, via put_page().
*
* @vmas are valid only as long as mmap_lock is held.
*
* Must be called with mmap_lock held for read or write.
*
* get_user_pages_remote walks a process's page tables and takes a reference
* to each struct page that each user address corresponds to at a given
* instant. That is, it takes the page that would be accessed if a user
* thread accesses the given user virtual address at that instant.
*
* This does not guarantee that the page exists in the user mappings when
* get_user_pages_remote returns, and there may even be a completely different
* page there in some cases (eg. if mmapped pagecache has been invalidated
* and subsequently re faulted). However it does guarantee that the page
* won't be freed completely. And mostly callers simply care that the page
* contains data that was valid *at some point in time*. Typically, an IO
* or similar operation cannot guarantee anything stronger anyway because
* locks can't be held over the syscall boundary.
*
* If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
* be called after the page is finished with, and before put_page is called.
*
* get_user_pages_remote is typically used for fewer-copy IO operations,
* to get a handle on the memory by some means other than accesses
* via the user virtual addresses. The pages may be submitted for
* DMA to devices or accessed via their kernel linear mapping (via the
* kmap APIs). Care should be taken to use the correct cache flushing APIs.
*
* See also get_user_pages_fast, for performance critical applications.
*
* get_user_pages_remote should be phased out in favor of
* get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
* should use get_user_pages_remote because it cannot pass
* FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
*/
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
if (!is_valid_gup_flags(gup_flags))
return -EINVAL;
return __get_user_pages_remote(mm, start, nr_pages, gup_flags,
pages, vmas, locked);
}
EXPORT_SYMBOL(get_user_pages_remote);
#else /* CONFIG_MMU */
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
return 0;
}
static long __get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
return 0;
}
#endif /* !CONFIG_MMU */
/**
* get_user_pages() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @vmas: array of pointers to vmas corresponding to each page.
* Or NULL if the caller does not require them.
*
* This is the same as get_user_pages_remote(), just with a less-flexible
* calling convention where we assume that the mm being operated on belongs to
* the current task, and doesn't allow passing of a locked parameter. We also
* obviously don't pass FOLL_REMOTE in here.
*/
long get_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas)
{
if (!is_valid_gup_flags(gup_flags))
return -EINVAL;
return __gup_longterm_locked(current->mm, start, nr_pages,
pages, vmas, gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(get_user_pages);
/**
* get_user_pages_locked() - variant of get_user_pages()
*
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
*
* It is suitable to replace the form:
*
* mmap_read_lock(mm);
* do_something()
* get_user_pages(mm, ..., pages, NULL);
* mmap_read_unlock(mm);
*
* to:
*
* int locked = 1;
* mmap_read_lock(mm);
* do_something()
* get_user_pages_locked(mm, ..., pages, &locked);
* if (locked)
* mmap_read_unlock(mm);
*
* We can leverage the VM_FAULT_RETRY functionality in the page fault
* paths better by using either get_user_pages_locked() or
* get_user_pages_unlocked().
*
*/
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
/*
* FIXME: Current FOLL_LONGTERM behavior is incompatible with
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
* vmas. As there are no users of this flag in this call we simply
* disallow this option for now.
*/
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
return -EINVAL;
/*
* FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
* never directly by the caller, so enforce that:
*/
if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
return -EINVAL;
return __get_user_pages_locked(current->mm, start, nr_pages,
pages, NULL, locked,
gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(get_user_pages_locked);
/*
* get_user_pages_unlocked() is suitable to replace the form:
*
* mmap_read_lock(mm);
* get_user_pages(mm, ..., pages, NULL);
* mmap_read_unlock(mm);
*
* with:
*
* get_user_pages_unlocked(mm, ..., pages);
*
* It is functionally equivalent to get_user_pages_fast so
* get_user_pages_fast should be used instead if specific gup_flags
* (e.g. FOLL_FORCE) are not required.
*/
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags)
{
struct mm_struct *mm = current->mm;
int locked = 1;
long ret;
/*
* FIXME: Current FOLL_LONGTERM behavior is incompatible with
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
* vmas. As there are no users of this flag in this call we simply
* disallow this option for now.
*/
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
return -EINVAL;
mmap_read_lock(mm);
ret = __get_user_pages_locked(mm, start, nr_pages, pages, NULL,
&locked, gup_flags | FOLL_TOUCH);
if (locked)
mmap_read_unlock(mm);
return ret;
}
EXPORT_SYMBOL(get_user_pages_unlocked);
/*
* Fast GUP
*
* get_user_pages_fast attempts to pin user pages by walking the page
* tables directly and avoids taking locks. Thus the walker needs to be
* protected from page table pages being freed from under it, and should
* block any THP splits.
*
* One way to achieve this is to have the walker disable interrupts, and
* rely on IPIs from the TLB flushing code blocking before the page table
* pages are freed. This is unsuitable for architectures that do not need
* to broadcast an IPI when invalidating TLBs.
*
* Another way to achieve this is to batch up page table containing pages
* belonging to more than one mm_user, then rcu_sched a callback to free those
* pages. Disabling interrupts will allow the fast_gup walker to both block
* the rcu_sched callback, and an IPI that we broadcast for splitting THPs
* (which is a relatively rare event). The code below adopts this strategy.
*
* Before activating this code, please be aware that the following assumptions
* are currently made:
*
* *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
* free pages containing page tables or TLB flushing requires IPI broadcast.
*
* *) ptes can be read atomically by the architecture.
*
* *) access_ok is sufficient to validate userspace address ranges.
*
* The last two assumptions can be relaxed by the addition of helper functions.
*
* This code is based heavily on the PowerPC implementation by Nick Piggin.
*/
#ifdef CONFIG_HAVE_FAST_GUP
static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
unsigned int flags,
struct page **pages)
{
while ((*nr) - nr_start) {
struct page *page = pages[--(*nr)];
ClearPageReferenced(page);
if (flags & FOLL_PIN)
unpin_user_page(page);
else
put_page(page);
}
}
#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
/*
* Fast-gup relies on pte change detection to avoid concurrent pgtable
* operations.
*
* To pin the page, fast-gup needs to do below in order:
* (1) pin the page (by prefetching pte), then (2) check pte not changed.
*
* For the rest of pgtable operations where pgtable updates can be racy
* with fast-gup, we need to do (1) clear pte, then (2) check whether page
* is pinned.
*
* Above will work for all pte-level operations, including THP split.
*
* For THP collapse, it's a bit more complicated because fast-gup may be
* walking a pgtable page that is being freed (pte is still valid but pmd
* can be cleared already). To avoid race in such condition, we need to
* also check pmd here to make sure pmd doesn't change (corresponds to
* pmdp_collapse_flush() in the THP collapse code path).
*/
static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
struct dev_pagemap *pgmap = NULL;
int nr_start = *nr, ret = 0;
pte_t *ptep, *ptem;
ptem = ptep = pte_offset_map(&pmd, addr);
do {
pte_t pte = ptep_get_lockless(ptep);
struct page *head, *page;
/*
* Similar to the PMD case below, NUMA hinting must take slow
* path using the pte_protnone check.
*/
if (pte_protnone(pte))
goto pte_unmap;
if (!pte_access_permitted(pte, flags & FOLL_WRITE))
goto pte_unmap;
if (pte_devmap(pte)) {
if (unlikely(flags & FOLL_LONGTERM))
goto pte_unmap;
pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
goto pte_unmap;
}
} else if (pte_special(pte))
goto pte_unmap;
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = pte_page(pte);
head = try_grab_compound_head(page, 1, flags);
if (!head)
goto pte_unmap;
if (unlikely(page_is_secretmem(page))) {
put_compound_head(head, 1, flags);
goto pte_unmap;
}
if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) ||
unlikely(pte_val(pte) != pte_val(*ptep))) {
put_compound_head(head, 1, flags);
goto pte_unmap;
}
VM_BUG_ON_PAGE(compound_head(page) != head, page);
/*
* We need to make the page accessible if and only if we are
* going to access its content (the FOLL_PIN case). Please
* see Documentation/core-api/pin_user_pages.rst for
* details.
*/
if (flags & FOLL_PIN) {
ret = arch_make_page_accessible(page);
if (ret) {
unpin_user_page(page);
goto pte_unmap;
}
}
SetPageReferenced(page);
pages[*nr] = page;
(*nr)++;
} while (ptep++, addr += PAGE_SIZE, addr != end);
ret = 1;
pte_unmap:
if (pgmap)
put_dev_pagemap(pgmap);
pte_unmap(ptem);
return ret;
}
#else
/*
* If we can't determine whether or not a pte is special, then fail immediately
* for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
* to be special.
*
* For a futex to be placed on a THP tail page, get_futex_key requires a
* get_user_pages_fast_only implementation that can pin pages. Thus it's still
* useful to have gup_huge_pmd even if we can't operate on ptes.
*/
static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
return 0;
}
#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
int nr_start = *nr;
struct dev_pagemap *pgmap = NULL;
int ret = 1;
do {
struct page *page = pfn_to_page(pfn);
pgmap = get_dev_pagemap(pfn, pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
ret = 0;
break;
}
SetPageReferenced(page);
pages[*nr] = page;
if (unlikely(!try_grab_page(page, flags))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
ret = 0;
break;
}
(*nr)++;
pfn++;
} while (addr += PAGE_SIZE, addr != end);
put_dev_pagemap(pgmap);
return ret;
}
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
unsigned long fault_pfn;
int nr_start = *nr;
fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
return 0;
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
return 0;
}
return 1;
}
static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
unsigned long fault_pfn;
int nr_start = *nr;
fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
return 0;
if (unlikely(pud_val(orig) != pud_val(*pudp))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
return 0;
}
return 1;
}
#else
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
BUILD_BUG();
return 0;
}
static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
BUILD_BUG();
return 0;
}
#endif
static int record_subpages(struct page *page, unsigned long addr,
unsigned long end, struct page **pages)
{
int nr;
for (nr = 0; addr != end; addr += PAGE_SIZE)
pages[nr++] = page++;
return nr;
}
#ifdef CONFIG_ARCH_HAS_HUGEPD
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
{
unsigned long __boundary = (addr + sz) & ~(sz-1);
return (__boundary - 1 < end - 1) ? __boundary : end;
}
static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
unsigned long pte_end;
struct page *head, *page;
pte_t pte;
int refs;
pte_end = (addr + sz) & ~(sz-1);
if (pte_end < end)
end = pte_end;
pte = huge_ptep_get(ptep);
if (!pte_access_permitted(pte, flags & FOLL_WRITE))
return 0;
/* hugepages are never "special" */
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
head = pte_page(pte);
page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
head = try_grab_compound_head(head, refs, flags);
if (!head)
return 0;
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
put_compound_head(head, refs, flags);
return 0;
}
*nr += refs;
SetPageReferenced(head);
return 1;
}
static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
unsigned int pdshift, unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
pte_t *ptep;
unsigned long sz = 1UL << hugepd_shift(hugepd);
unsigned long next;
ptep = hugepte_offset(hugepd, addr, pdshift);
do {
next = hugepte_addr_end(addr, end, sz);
if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
return 0;
} while (ptep++, addr = next, addr != end);
return 1;
}
#else
static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
unsigned int pdshift, unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
return 0;
}
#endif /* CONFIG_ARCH_HAS_HUGEPD */
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
struct page *head, *page;
int refs;
if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
return 0;
if (pmd_devmap(orig)) {
if (unlikely(flags & FOLL_LONGTERM))
return 0;
return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
pages, nr);
}
page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
head = try_grab_compound_head(pmd_page(orig), refs, flags);
if (!head)
return 0;
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
put_compound_head(head, refs, flags);
return 0;
}
*nr += refs;
SetPageReferenced(head);
return 1;
}
static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
struct page *head, *page;
int refs;
if (!pud_access_permitted(orig, flags & FOLL_WRITE))
return 0;
if (pud_devmap(orig)) {
if (unlikely(flags & FOLL_LONGTERM))
return 0;
return __gup_device_huge_pud(orig, pudp, addr, end, flags,
pages, nr);
}
page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
head = try_grab_compound_head(pud_page(orig), refs, flags);
if (!head)
return 0;
if (unlikely(pud_val(orig) != pud_val(*pudp))) {
put_compound_head(head, refs, flags);
return 0;
}
*nr += refs;
SetPageReferenced(head);
return 1;
}
static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
int refs;
struct page *head, *page;
if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
return 0;
BUILD_BUG_ON(pgd_devmap(orig));
page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
head = try_grab_compound_head(pgd_page(orig), refs, flags);
if (!head)
return 0;
if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
put_compound_head(head, refs, flags);
return 0;
}
*nr += refs;
SetPageReferenced(head);
return 1;
}
static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pmd_t *pmdp;
pmdp = pmd_offset_lockless(pudp, pud, addr);
do {
pmd_t pmd = READ_ONCE(*pmdp);
next = pmd_addr_end(addr, end);
if (!pmd_present(pmd))
return 0;
if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
pmd_devmap(pmd))) {
/*
* NUMA hinting faults need to be handled in the GUP
* slowpath for accounting purposes and so that they
* can be serialised against THP migration.
*/
if (pmd_protnone(pmd))
return 0;
if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
pages, nr))
return 0;
} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
/*
* architecture have different format for hugetlbfs
* pmd format and THP pmd format
*/
if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
PMD_SHIFT, next, flags, pages, nr))
return 0;
} else if (!gup_pte_range(pmd, pmdp, addr, next, flags, pages, nr))
return 0;
} while (pmdp++, addr = next, addr != end);
return 1;
}
static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pud_t *pudp;
pudp = pud_offset_lockless(p4dp, p4d, addr);
do {
pud_t pud = READ_ONCE(*pudp);
next = pud_addr_end(addr, end);
if (unlikely(!pud_present(pud)))
return 0;
if (unlikely(pud_huge(pud))) {
if (!gup_huge_pud(pud, pudp, addr, next, flags,
pages, nr))
return 0;
} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
PUD_SHIFT, next, flags, pages, nr))
return 0;
} else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr))
return 0;
} while (pudp++, addr = next, addr != end);
return 1;
}
static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
p4d_t *p4dp;
p4dp = p4d_offset_lockless(pgdp, pgd, addr);
do {
p4d_t p4d = READ_ONCE(*p4dp);
next = p4d_addr_end(addr, end);
if (p4d_none(p4d))
return 0;
BUILD_BUG_ON(p4d_huge(p4d));
if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
P4D_SHIFT, next, flags, pages, nr))
return 0;
} else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr))
return 0;
} while (p4dp++, addr = next, addr != end);
return 1;
}
static void gup_pgd_range(unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pgd_t *pgdp;
pgdp = pgd_offset(current->mm, addr);
do {
pgd_t pgd = READ_ONCE(*pgdp);
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
return;
if (unlikely(pgd_huge(pgd))) {
if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
pages, nr))
return;
} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
PGDIR_SHIFT, next, flags, pages, nr))
return;
} else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr))
return;
} while (pgdp++, addr = next, addr != end);
}
#else
static inline void gup_pgd_range(unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
}
#endif /* CONFIG_HAVE_FAST_GUP */
#ifndef gup_fast_permitted
/*
* Check if it's allowed to use get_user_pages_fast_only() for the range, or
* we need to fall back to the slow version:
*/
static bool gup_fast_permitted(unsigned long start, unsigned long end)
{
return true;
}
#endif
static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
int ret;
/*
* FIXME: FOLL_LONGTERM does not work with
* get_user_pages_unlocked() (see comments in that function)
*/
if (gup_flags & FOLL_LONGTERM) {
mmap_read_lock(current->mm);
ret = __gup_longterm_locked(current->mm,
start, nr_pages,
pages, NULL, gup_flags);
mmap_read_unlock(current->mm);
} else {
ret = get_user_pages_unlocked(start, nr_pages,
pages, gup_flags);
}
return ret;
}
static unsigned long lockless_pages_from_mm(unsigned long start,
unsigned long end,
unsigned int gup_flags,
struct page **pages)
{
unsigned long flags;
int nr_pinned = 0;
unsigned seq;
if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
!gup_fast_permitted(start, end))
return 0;
if (gup_flags & FOLL_PIN) {
seq = raw_read_seqcount(&current->mm->write_protect_seq);
if (seq & 1)
return 0;
}
/*
* Disable interrupts. The nested form is used, in order to allow full,
* general purpose use of this routine.
*
* With interrupts disabled, we block page table pages from being freed
* from under us. See struct mmu_table_batch comments in
* include/asm-generic/tlb.h for more details.
*
* We do not adopt an rcu_read_lock() here as we also want to block IPIs
* that come from THPs splitting.
*/
local_irq_save(flags);
gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
local_irq_restore(flags);
/*
* When pinning pages for DMA there could be a concurrent write protect
* from fork() via copy_page_range(), in this case always fail fast GUP.
*/
if (gup_flags & FOLL_PIN) {
if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
unpin_user_pages(pages, nr_pinned);
return 0;
}
}
return nr_pinned;
}
static int internal_get_user_pages_fast(unsigned long start,
unsigned long nr_pages,
unsigned int gup_flags,
struct page **pages)
{
unsigned long len, end;
unsigned long nr_pinned;
int ret;
if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
FOLL_FORCE | FOLL_PIN | FOLL_GET |
FOLL_FAST_ONLY | FOLL_NOFAULT)))
return -EINVAL;
if (gup_flags & FOLL_PIN)
mm_set_has_pinned_flag(&current->mm->flags);
if (!(gup_flags & FOLL_FAST_ONLY))
might_lock_read(&current->mm->mmap_lock);
start = untagged_addr(start) & PAGE_MASK;
len = nr_pages << PAGE_SHIFT;
if (check_add_overflow(start, len, &end))
return 0;
if (unlikely(!access_ok((void __user *)start, len)))
return -EFAULT;
nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
return nr_pinned;
/* Slow path: try to get the remaining pages with get_user_pages */
start += nr_pinned << PAGE_SHIFT;
pages += nr_pinned;
ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned, gup_flags,
pages);
if (ret < 0) {
/*
* The caller has to unpin the pages we already pinned so
* returning -errno is not an option
*/
if (nr_pinned)
return nr_pinned;
return ret;
}
return ret + nr_pinned;
}
/**
* get_user_pages_fast_only() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
* the regular GUP.
* Note a difference with get_user_pages_fast: this always returns the
* number of pages pinned, 0 if no pages were pinned.
*
* If the architecture does not support this function, simply return with no
* pages pinned.
*
* Careful, careful! COW breaking can go either way, so a non-write
* access can get ambiguous page results. If you call this function without
* 'write' set, you'd better be sure that you're ok with that ambiguity.
*/
int get_user_pages_fast_only(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
int nr_pinned;
/*
* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
* because gup fast is always a "pin with a +1 page refcount" request.
*
* FOLL_FAST_ONLY is required in order to match the API description of
* this routine: no fall back to regular ("slow") GUP.
*/
gup_flags |= FOLL_GET | FOLL_FAST_ONLY;
nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
pages);
/*
* As specified in the API description above, this routine is not
* allowed to return negative values. However, the common core
* routine internal_get_user_pages_fast() *can* return -errno.
* Therefore, correct for that here:
*/
if (nr_pinned < 0)
nr_pinned = 0;
return nr_pinned;
}
EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
/**
* get_user_pages_fast() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Attempt to pin user pages in memory without taking mm->mmap_lock.
* If not successful, it will fall back to taking the lock and
* calling get_user_pages().
*
* Returns number of pages pinned. This may be fewer than the number requested.
* If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
* -errno.
*/
int get_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
if (!is_valid_gup_flags(gup_flags))
return -EINVAL;
/*
* The caller may or may not have explicitly set FOLL_GET; either way is
* OK. However, internally (within mm/gup.c), gup fast variants must set
* FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
* request.
*/
gup_flags |= FOLL_GET;
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
EXPORT_SYMBOL_GPL(get_user_pages_fast);
/**
* pin_user_pages_fast() - pin user pages in memory without taking locks
*
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
* get_user_pages_fast() for documentation on the function arguments, because
* the arguments here are identical.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for further details.
*/
int pin_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return -EINVAL;
gup_flags |= FOLL_PIN;
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
EXPORT_SYMBOL_GPL(pin_user_pages_fast);
/*
* This is the FOLL_PIN equivalent of get_user_pages_fast_only(). Behavior
* is the same, except that this one sets FOLL_PIN instead of FOLL_GET.
*
* The API rules are the same, too: no negative values may be returned.
*/
int pin_user_pages_fast_only(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
int nr_pinned;
/*
* FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API
* rules require returning 0, rather than -errno:
*/
if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return 0;
/*
* FOLL_FAST_ONLY is required in order to match the API description of
* this routine: no fall back to regular ("slow") GUP.
*/
gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY);
nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
pages);
/*
* This routine is not allowed to return negative values. However,
* internal_get_user_pages_fast() *can* return -errno. Therefore,
* correct for that here:
*/
if (nr_pinned < 0)
nr_pinned = 0;
return nr_pinned;
}
EXPORT_SYMBOL_GPL(pin_user_pages_fast_only);
/**
* pin_user_pages_remote() - pin pages of a remote process
*
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @vmas: array of pointers to vmas corresponding to each page.
* Or NULL if the caller does not require them.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
*
* Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
* get_user_pages_remote() for documentation on the function arguments, because
* the arguments here are identical.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
*/
long pin_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return -EINVAL;
gup_flags |= FOLL_PIN;
return __get_user_pages_remote(mm, start, nr_pages, gup_flags,
pages, vmas, locked);
}
EXPORT_SYMBOL(pin_user_pages_remote);
/**
* pin_user_pages() - pin user pages in memory for use by other devices
*
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @vmas: array of pointers to vmas corresponding to each page.
* Or NULL if the caller does not require them.
*
* Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
* FOLL_PIN is set.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
*/
long pin_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas)
{
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return -EINVAL;
gup_flags |= FOLL_PIN;
return __gup_longterm_locked(current->mm, start, nr_pages,
pages, vmas, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages);
/*
* pin_user_pages_unlocked() is the FOLL_PIN variant of
* get_user_pages_unlocked(). Behavior is the same, except that this one sets
* FOLL_PIN and rejects FOLL_GET.
*/
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags)
{
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return -EINVAL;
gup_flags |= FOLL_PIN;
return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages_unlocked);
/*
* pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
* Behavior is the same, except that this one sets FOLL_PIN and rejects
* FOLL_GET.
*/
long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
/*
* FIXME: Current FOLL_LONGTERM behavior is incompatible with
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
* vmas. As there are no users of this flag in this call we simply
* disallow this option for now.
*/
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
return -EINVAL;
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return -EINVAL;
gup_flags |= FOLL_PIN;
return __get_user_pages_locked(current->mm, start, nr_pages,
pages, NULL, locked,
gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(pin_user_pages_locked);