add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}
-static inline bool is_cow_mapping(vm_flags_t flags)
-{
- return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
-}
-
/*
* vm_normal_page -- This function gets the "struct page" associated with a pte.
*
unsigned long pfn = pte_pfn(pte);
if (HAVE_PTE_SPECIAL) {
- if (likely(!pte_special(pte)))
+ if (likely(!pte_special(pte) || pte_numa(pte)))
goto check_pfn;
if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return NULL;
}
}
- if (is_zero_pfn(pfn))
- return NULL;
check_pfn:
if (unlikely(pfn > highest_memmap_pfn)) {
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
+ if (is_zero_pfn(pfn))
+ return NULL;
+
/*
* NOTE! We still have PageReserved() pages in the page tables.
* eg. VDSO mappings can cause them to exist.
}
EXPORT_SYMBOL_GPL(zap_vma_ptes);
-/**
- * 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
- * @page_mask: on output, *page_mask is set according to the size of the page
- *
- * @flags can have FOLL_ flags set, defined in <linux/mm.h>
- *
- * Returns 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()).
- */
-struct page *follow_page_mask(struct vm_area_struct *vma,
- unsigned long address, unsigned int flags,
- unsigned int *page_mask)
-{
- pgd_t *pgd;
- pud_t *pud;
- pmd_t *pmd;
- pte_t *ptep, pte;
- spinlock_t *ptl;
- struct page *page;
- struct mm_struct *mm = vma->vm_mm;
-
- *page_mask = 0;
-
- page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
- if (!IS_ERR(page)) {
- BUG_ON(flags & FOLL_GET);
- goto out;
- }
-
- page = NULL;
- pgd = pgd_offset(mm, address);
- if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
- goto no_page_table;
-
- pud = pud_offset(pgd, address);
- if (pud_none(*pud))
- goto no_page_table;
- if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
- if (flags & FOLL_GET)
- goto out;
- page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
- goto out;
- }
- if (unlikely(pud_bad(*pud)))
- goto no_page_table;
-
- pmd = pmd_offset(pud, address);
- if (pmd_none(*pmd))
- goto no_page_table;
- if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
- page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
- if (flags & FOLL_GET) {
- /*
- * Refcount on tail pages are not well-defined and
- * shouldn't be taken. The caller should handle a NULL
- * return when trying to follow tail pages.
- */
- if (PageHead(page))
- get_page(page);
- else {
- page = NULL;
- goto out;
- }
- }
- goto out;
- }
- if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
- goto no_page_table;
- if (pmd_trans_huge(*pmd)) {
- if (flags & FOLL_SPLIT) {
- split_huge_page_pmd(vma, address, pmd);
- goto split_fallthrough;
- }
- ptl = pmd_lock(mm, pmd);
- if (likely(pmd_trans_huge(*pmd))) {
- if (unlikely(pmd_trans_splitting(*pmd))) {
- spin_unlock(ptl);
- wait_split_huge_page(vma->anon_vma, pmd);
- } else {
- page = follow_trans_huge_pmd(vma, address,
- pmd, flags);
- spin_unlock(ptl);
- *page_mask = HPAGE_PMD_NR - 1;
- goto out;
- }
- } else
- spin_unlock(ptl);
- /* fall through */
- }
-split_fallthrough:
- if (unlikely(pmd_bad(*pmd)))
- goto no_page_table;
-
- 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) || pte_file(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 split_fallthrough;
- }
- if ((flags & FOLL_NUMA) && pte_numa(pte))
- goto no_page;
- if ((flags & FOLL_WRITE) && !pte_write(pte))
- goto unlock;
-
- page = vm_normal_page(vma, address, pte);
- if (unlikely(!page)) {
- if ((flags & FOLL_DUMP) ||
- !is_zero_pfn(pte_pfn(pte)))
- goto bad_page;
- page = pte_page(pte);
- }
-
- if (flags & FOLL_GET)
- get_page_foll(page);
- 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)) {
- /*
- * 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);
- }
- }
-unlock:
- pte_unmap_unlock(ptep, ptl);
-out:
- return page;
-
-bad_page:
- pte_unmap_unlock(ptep, ptl);
- return ERR_PTR(-EFAULT);
-
-no_page:
- pte_unmap_unlock(ptep, ptl);
- if (!pte_none(pte))
- return page;
-
-no_page_table:
- /*
- * 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->vm_ops || !vma->vm_ops->fault))
- return ERR_PTR(-EFAULT);
- return page;
-}
-
-static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
-{
- return stack_guard_page_start(vma, addr) ||
- stack_guard_page_end(vma, addr+PAGE_SIZE);
-}
-
-/**
- * __get_user_pages() - pin user pages in memory
- * @tsk: task_struct of target task
- * @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.
- * @nonblocking: whether waiting for disk IO or mmap_sem contention
- *
- * 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. Each page returned must be released
- * with a put_page() call when it is finished with. vmas will only
- * remain valid while mmap_sem is held.
- *
- * Must be called with mmap_sem held for read or write.
- *
- * __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 @nonblocking != NULL, __get_user_pages will not wait for disk IO
- * or mmap_sem contention, and if waiting is needed to pin all pages,
- * *@nonblocking will be set to 0.
- *
- * 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.
- */
-long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, unsigned long nr_pages,
- unsigned int gup_flags, struct page **pages,
- struct vm_area_struct **vmas, int *nonblocking)
-{
- long i;
- unsigned long vm_flags;
- unsigned int page_mask;
-
- if (!nr_pages)
- return 0;
-
- VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
-
- /*
- * If FOLL_FORCE and FOLL_NUMA are both set, handle_mm_fault
- * would be called on PROT_NONE ranges. We must never invoke
- * handle_mm_fault on PROT_NONE ranges or the NUMA hinting
- * page faults would unprotect the PROT_NONE ranges if
- * _PAGE_NUMA and _PAGE_PROTNONE are sharing the same pte/pmd
- * bitflag. So to avoid that, don't set FOLL_NUMA if
- * FOLL_FORCE is set.
- */
- if (!(gup_flags & FOLL_FORCE))
- gup_flags |= FOLL_NUMA;
-
- i = 0;
-
- do {
- struct vm_area_struct *vma;
-
- vma = find_extend_vma(mm, start);
- if (!vma && in_gate_area(mm, start)) {
- unsigned long pg = start & PAGE_MASK;
- pgd_t *pgd;
- pud_t *pud;
- pmd_t *pmd;
- pte_t *pte;
-
- /* user gate pages are read-only */
- if (gup_flags & FOLL_WRITE)
- goto efault;
- if (pg > TASK_SIZE)
- pgd = pgd_offset_k(pg);
- else
- pgd = pgd_offset_gate(mm, pg);
- BUG_ON(pgd_none(*pgd));
- pud = pud_offset(pgd, pg);
- BUG_ON(pud_none(*pud));
- pmd = pmd_offset(pud, pg);
- if (pmd_none(*pmd))
- goto efault;
- VM_BUG_ON(pmd_trans_huge(*pmd));
- pte = pte_offset_map(pmd, pg);
- if (pte_none(*pte)) {
- pte_unmap(pte);
- goto efault;
- }
- vma = get_gate_vma(mm);
- if (pages) {
- struct page *page;
-
- page = vm_normal_page(vma, start, *pte);
- if (!page) {
- if (!(gup_flags & FOLL_DUMP) &&
- is_zero_pfn(pte_pfn(*pte)))
- page = pte_page(*pte);
- else {
- pte_unmap(pte);
- goto efault;
- }
- }
- pages[i] = page;
- get_page(page);
- }
- pte_unmap(pte);
- page_mask = 0;
- goto next_page;
- }
-
- if (!vma)
- goto efault;
- vm_flags = vma->vm_flags;
- if (vm_flags & (VM_IO | VM_PFNMAP))
- goto efault;
-
- if (gup_flags & FOLL_WRITE) {
- if (!(vm_flags & VM_WRITE)) {
- if (!(gup_flags & FOLL_FORCE))
- goto 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)) {
- WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
- goto efault;
- }
- }
- } else {
- if (!(vm_flags & VM_READ)) {
- if (!(gup_flags & FOLL_FORCE))
- goto efault;
- /*
- * Is there actually any vma we can reach here
- * which does not have VM_MAYREAD set?
- */
- if (!(vm_flags & VM_MAYREAD))
- goto efault;
- }
- }
-
- if (is_vm_hugetlb_page(vma)) {
- i = follow_hugetlb_page(mm, vma, pages, vmas,
- &start, &nr_pages, i, gup_flags);
- continue;
- }
-
- do {
- struct page *page;
- unsigned int foll_flags = gup_flags;
- unsigned int page_increm;
-
- /*
- * If we have a pending SIGKILL, don't keep faulting
- * pages and potentially allocating memory.
- */
- if (unlikely(fatal_signal_pending(current)))
- return i ? i : -ERESTARTSYS;
-
- cond_resched();
- while (!(page = follow_page_mask(vma, start,
- foll_flags, &page_mask))) {
- int ret;
- unsigned int fault_flags = 0;
-
- /* For mlock, just skip the stack guard page. */
- if (foll_flags & FOLL_MLOCK) {
- if (stack_guard_page(vma, start))
- goto next_page;
- }
- if (foll_flags & FOLL_WRITE)
- fault_flags |= FAULT_FLAG_WRITE;
- if (nonblocking)
- fault_flags |= FAULT_FLAG_ALLOW_RETRY;
- if (foll_flags & FOLL_NOWAIT)
- fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
-
- ret = handle_mm_fault(mm, vma, start,
- fault_flags);
-
- if (ret & VM_FAULT_ERROR) {
- if (ret & VM_FAULT_OOM)
- return i ? i : -ENOMEM;
- if (ret & (VM_FAULT_HWPOISON |
- VM_FAULT_HWPOISON_LARGE)) {
- if (i)
- return i;
- else if (gup_flags & FOLL_HWPOISON)
- return -EHWPOISON;
- else
- return -EFAULT;
- }
- if (ret & VM_FAULT_SIGBUS)
- goto efault;
- BUG();
- }
-
- if (tsk) {
- if (ret & VM_FAULT_MAJOR)
- tsk->maj_flt++;
- else
- tsk->min_flt++;
- }
-
- if (ret & VM_FAULT_RETRY) {
- if (nonblocking)
- *nonblocking = 0;
- return i;
- }
-
- /*
- * 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))
- foll_flags &= ~FOLL_WRITE;
-
- cond_resched();
- }
- if (IS_ERR(page))
- return i ? i : PTR_ERR(page);
- if (pages) {
- pages[i] = page;
-
- flush_anon_page(vma, page, start);
- flush_dcache_page(page);
- page_mask = 0;
- }
-next_page:
- if (vmas) {
- vmas[i] = vma;
- page_mask = 0;
- }
- page_increm = 1 + (~(start >> PAGE_SHIFT) & 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 && start < vma->vm_end);
- } while (nr_pages);
- return i;
-efault:
- return i ? : -EFAULT;
-}
-EXPORT_SYMBOL(__get_user_pages);
-
-/*
- * fixup_user_fault() - manually resolve a user page fault
- * @tsk: the task_struct to use for page fault accounting, or
- * NULL if faults are not to be recorded.
- * @mm: mm_struct of target mm
- * @address: user address
- * @fault_flags:flags to pass down to handle_mm_fault()
- *
- * 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
- * handle_mm_fault() 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 should be called with the mm_sem held for read.
- */
-int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long address, unsigned int fault_flags)
-{
- struct vm_area_struct *vma;
- vm_flags_t vm_flags;
- int ret;
-
- vma = find_extend_vma(mm, address);
- if (!vma || address < vma->vm_start)
- return -EFAULT;
-
- vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
- if (!(vm_flags & vma->vm_flags))
- return -EFAULT;
-
- ret = handle_mm_fault(mm, vma, address, fault_flags);
- if (ret & VM_FAULT_ERROR) {
- if (ret & VM_FAULT_OOM)
- return -ENOMEM;
- if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
- return -EHWPOISON;
- if (ret & VM_FAULT_SIGBUS)
- return -EFAULT;
- BUG();
- }
- if (tsk) {
- if (ret & VM_FAULT_MAJOR)
- tsk->maj_flt++;
- else
- tsk->min_flt++;
- }
- return 0;
-}
-
-/*
- * get_user_pages() - pin user pages in memory
- * @tsk: the task_struct to use for page fault accounting, or
- * NULL if faults are not to be recorded.
- * @mm: mm_struct of target mm
- * @start: starting user address
- * @nr_pages: number of pages from start to pin
- * @write: whether pages will be written to by the caller
- * @force: whether to force access even when user mapping is currently
- * protected (but never forces write access to shared mapping).
- * @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.
- *
- * 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. Each page returned must be released
- * with a put_page() call when it is finished with. vmas will only
- * remain valid while mmap_sem is held.
- *
- * Must be called with mmap_sem held for read or write.
- *
- * 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 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 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.
- */
-long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, unsigned long nr_pages, int write,
- int force, struct page **pages, struct vm_area_struct **vmas)
-{
- int flags = FOLL_TOUCH;
-
- if (pages)
- flags |= FOLL_GET;
- if (write)
- flags |= FOLL_WRITE;
- if (force)
- flags |= FOLL_FORCE;
-
- return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
- NULL);
-}
-EXPORT_SYMBOL(get_user_pages);
-
-/**
- * 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 page_cache_release() or 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 diskspace.
- *
- * Called without mmap_sem, but after all other threads have been killed.
- */
-#ifdef CONFIG_ELF_CORE
-struct page *get_dump_page(unsigned long addr)
-{
- struct vm_area_struct *vma;
- struct page *page;
-
- if (__get_user_pages(current, current->mm, addr, 1,
- FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
- NULL) < 1)
- return NULL;
- flush_cache_page(vma, addr, page_to_pfn(page));
- return page;
-}
-#endif /* CONFIG_ELF_CORE */
-
pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
spinlock_t **ptl)
{
update_mmu_cache(vma, address, pte);
}
-#define FAULT_AROUND_ORDER 4
+static unsigned long fault_around_bytes = 65536;
+
+/*
+ * fault_around_pages() and fault_around_mask() round down fault_around_bytes
+ * to nearest page order. It's what do_fault_around() expects to see.
+ */
+static inline unsigned long fault_around_pages(void)
+{
+ return rounddown_pow_of_two(fault_around_bytes) / PAGE_SIZE;
+}
+
+static inline unsigned long fault_around_mask(void)
+{
+ return ~(rounddown_pow_of_two(fault_around_bytes) - 1) & PAGE_MASK;
+}
-#ifdef CONFIG_DEBUG_FS
-static unsigned int fault_around_order = FAULT_AROUND_ORDER;
-static int fault_around_order_get(void *data, u64 *val)
+#ifdef CONFIG_DEBUG_FS
+static int fault_around_bytes_get(void *data, u64 *val)
{
- *val = fault_around_order;
+ *val = fault_around_bytes;
return 0;
}
-static int fault_around_order_set(void *data, u64 val)
+static int fault_around_bytes_set(void *data, u64 val)
{
- BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);
- if (1UL << val > PTRS_PER_PTE)
+ if (val / PAGE_SIZE > PTRS_PER_PTE)
return -EINVAL;
- fault_around_order = val;
+ fault_around_bytes = val;
return 0;
}
-DEFINE_SIMPLE_ATTRIBUTE(fault_around_order_fops,
- fault_around_order_get, fault_around_order_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,
+ fault_around_bytes_get, fault_around_bytes_set, "%llu\n");
static int __init fault_around_debugfs(void)
{
void *ret;
- ret = debugfs_create_file("fault_around_order", 0644, NULL, NULL,
- &fault_around_order_fops);
+ ret = debugfs_create_file("fault_around_bytes", 0644, NULL, NULL,
+ &fault_around_bytes_fops);
if (!ret)
- pr_warn("Failed to create fault_around_order in debugfs");
+ pr_warn("Failed to create fault_around_bytes in debugfs");
return 0;
}
late_initcall(fault_around_debugfs);
-
-static inline unsigned long fault_around_pages(void)
-{
- return 1UL << fault_around_order;
-}
-
-static inline unsigned long fault_around_mask(void)
-{
- return ~((1UL << (PAGE_SHIFT + fault_around_order)) - 1);
-}
-#else
-static inline unsigned long fault_around_pages(void)
-{
- unsigned long nr_pages;
-
- nr_pages = 1UL << FAULT_AROUND_ORDER;
- BUILD_BUG_ON(nr_pages > PTRS_PER_PTE);
- return nr_pages;
-}
-
-static inline unsigned long fault_around_mask(void)
-{
- return ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1);
-}
#endif
+/*
+ * do_fault_around() tries to map few pages around the fault address. The hope
+ * is that the pages will be needed soon and this will lower the number of
+ * faults to handle.
+ *
+ * It uses vm_ops->map_pages() to map the pages, which skips the page if it's
+ * not ready to be mapped: not up-to-date, locked, etc.
+ *
+ * This function is called with the page table lock taken. In the split ptlock
+ * case the page table lock only protects only those entries which belong to
+ * the page table corresponding to the fault address.
+ *
+ * This function doesn't cross the VMA boundaries, in order to call map_pages()
+ * only once.
+ *
+ * fault_around_pages() defines how many pages we'll try to map.
+ * do_fault_around() expects it to return a power of two less than or equal to
+ * PTRS_PER_PTE.
+ *
+ * The virtual address of the area that we map is naturally aligned to the
+ * fault_around_pages() value (and therefore to page order). This way it's
+ * easier to guarantee that we don't cross page table boundaries.
+ */
static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
pte_t *pte, pgoff_t pgoff, unsigned int flags)
{
/*
* max_pgoff is either end of page table or end of vma
- * or fault_around_pages() from pgoff, depending what is neast.
+ * or fault_around_pages() from pgoff, depending what is nearest.
*/
max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
PTRS_PER_PTE - 1;
* if page by the offset is not ready to be mapped (cold cache or
* something).
*/
- if (vma->vm_ops->map_pages) {
+ if (vma->vm_ops->map_pages && fault_around_pages() > 1) {
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
do_fault_around(vma, address, pte, pgoff, flags);
if (!pte_same(*pte, orig_pte))
projects / karo-tx-linux.git / blobdiff