* [PATCHv2 1/5] mm: move get_user_pages()-related code to separate file
2014-04-24 20:45 [PATCHv2 0/5] get_user_pages() cleanup Kirill A. Shutemov
@ 2014-04-24 20:45 ` Kirill A. Shutemov
2014-04-24 20:45 ` [PATCHv2 2/5] mm: extract in_gate_area() case from __get_user_pages() Kirill A. Shutemov
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Kirill A. Shutemov @ 2014-04-24 20:45 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, Jan Kara, Kirill A. Shutemov
mm/memory.c is overloaded: over 4k lines. get_user_pages() code is
pretty much self-contained let's move it to separate file.
No other changes made.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/Makefile | 2 +-
mm/gup.c | 653 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
mm/internal.h | 5 +
mm/memory.c | 645 ---------------------------------------------------------
4 files changed, 659 insertions(+), 646 deletions(-)
create mode 100644 mm/gup.c
diff --git a/mm/Makefile b/mm/Makefile
index b484452dac57..9bc26154557c 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -3,7 +3,7 @@
#
mmu-y := nommu.o
-mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
+mmu-$(CONFIG_MMU) := fremap.o gup.o highmem.o madvise.o memory.o mincore.o \
mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
vmalloc.o pagewalk.o pgtable-generic.o
diff --git a/mm/gup.c b/mm/gup.c
new file mode 100644
index 000000000000..2de1afaee435
--- /dev/null
+++ b/mm/gup.c
@@ -0,0 +1,653 @@
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+
+#include <linux/hugetlb.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+
+#include "internal.h"
+
+/**
+ * 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 */
diff --git a/mm/internal.h b/mm/internal.h
index 07b67361a40a..6ee580d69ddd 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -169,6 +169,11 @@ static inline unsigned long page_order(struct page *page)
return page_private(page);
}
+static inline bool is_cow_mapping(vm_flags_t flags)
+{
+ return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+}
+
/* mm/util.c */
void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev, struct rb_node *rb_parent);
diff --git a/mm/memory.c b/mm/memory.c
index 93e332d5ed77..c26a3f2bb256 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -689,11 +689,6 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
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.
*
@@ -1442,646 +1437,6 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
}
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)
{
--
1.9.2
--
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^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCHv2 3/5] mm: cleanup follow_page_mask()
2014-04-24 20:45 [PATCHv2 0/5] get_user_pages() cleanup Kirill A. Shutemov
2014-04-24 20:45 ` [PATCHv2 1/5] mm: move get_user_pages()-related code to separate file Kirill A. Shutemov
2014-04-24 20:45 ` [PATCHv2 2/5] mm: extract in_gate_area() case from __get_user_pages() Kirill A. Shutemov
@ 2014-04-24 20:45 ` Kirill A. Shutemov
2014-04-24 20:45 ` [PATCHv2 4/5] mm: extract code to fault in a page from __get_user_pages() Kirill A. Shutemov
2014-04-24 20:45 ` [PATCHv2 5/5] mm: cleanup __get_user_pages() Kirill A. Shutemov
4 siblings, 0 replies; 6+ messages in thread
From: Kirill A. Shutemov @ 2014-04-24 20:45 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, Jan Kara, Kirill A. Shutemov
Cleanups:
- move pte-related code to separate function. It's about half of the
function;
- get rid of some goto-logic;
- use 'return NULL' instead of 'return page' where page can only be
NULL;
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/gup.c | 231 ++++++++++++++++++++++++++++++++-------------------------------
1 file changed, 119 insertions(+), 112 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 7a1c4133b464..e0c648cbeee0 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -12,105 +12,35 @@
#include "internal.h"
-/**
- * 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)
+static struct page *no_page_table(struct vm_area_struct *vma,
+ unsigned int flags)
{
- 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;
+ /*
+ * 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 NULL;
+}
- 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;
+static struct page *follow_page_pte(struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd, unsigned int flags)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct page *page;
+ spinlock_t *ptl;
+ pte_t *ptep, pte;
- 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:
+retry:
if (unlikely(pmd_bad(*pmd)))
- goto no_page_table;
+ 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;
@@ -128,12 +58,14 @@ split_fallthrough:
goto no_page;
pte_unmap_unlock(ptep, ptl);
migration_entry_wait(mm, pmd, address);
- goto split_fallthrough;
+ goto retry;
}
if ((flags & FOLL_NUMA) && pte_numa(pte))
goto no_page;
- if ((flags & FOLL_WRITE) && !pte_write(pte))
- goto unlock;
+ if ((flags & FOLL_WRITE) && !pte_write(pte)) {
+ pte_unmap_unlock(ptep, ptl);
+ return NULL;
+ }
page = vm_normal_page(vma, address, pte);
if (unlikely(!page)) {
@@ -178,11 +110,8 @@ split_fallthrough:
unlock_page(page);
}
}
-unlock:
pte_unmap_unlock(ptep, ptl);
-out:
return page;
-
bad_page:
pte_unmap_unlock(ptep, ptl);
return ERR_PTR(-EFAULT);
@@ -190,21 +119,99 @@ bad_page:
no_page:
pte_unmap_unlock(ptep, ptl);
if (!pte_none(pte))
+ return NULL;
+ return no_page_table(vma, flags);
+}
+
+/**
+ * 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;
+ 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);
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;
+ pgd = pgd_offset(mm, address);
+ if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+ return no_page_table(vma, flags);
+
+ pud = pud_offset(pgd, address);
+ if (pud_none(*pud))
+ return no_page_table(vma, flags);
+ if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
+ if (flags & FOLL_GET)
+ return NULL;
+ page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
+ return page;
+ }
+ if (unlikely(pud_bad(*pud)))
+ return no_page_table(vma, flags);
+
+ pmd = pmd_offset(pud, address);
+ if (pmd_none(*pmd))
+ return no_page_table(vma, flags);
+ 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;
+ }
+ return page;
+ }
+ if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
+ return no_page_table(vma, flags);
+ if (pmd_trans_huge(*pmd)) {
+ if (flags & FOLL_SPLIT) {
+ split_huge_page_pmd(vma, address, pmd);
+ return follow_page_pte(vma, address, pmd, flags);
+ }
+ 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;
+ return page;
+ }
+ } else
+ spin_unlock(ptl);
+ }
+ return follow_page_pte(vma, address, pmd, flags);
}
static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
--
1.9.2
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCHv2 5/5] mm: cleanup __get_user_pages()
2014-04-24 20:45 [PATCHv2 0/5] get_user_pages() cleanup Kirill A. Shutemov
` (3 preceding siblings ...)
2014-04-24 20:45 ` [PATCHv2 4/5] mm: extract code to fault in a page from __get_user_pages() Kirill A. Shutemov
@ 2014-04-24 20:45 ` Kirill A. Shutemov
4 siblings, 0 replies; 6+ messages in thread
From: Kirill A. Shutemov @ 2014-04-24 20:45 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, Jan Kara, Kirill A. Shutemov
Get rid of two nested loops over nr_pages, extract vma flags checking to
separate function and other random cleanups.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/gup.c | 218 +++++++++++++++++++++++++++++++--------------------------------
1 file changed, 107 insertions(+), 111 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 8a4815380401..22036c28c6ec 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -315,6 +315,44 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
return 0;
}
+static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
+{
+ vm_flags_t vm_flags = vma->vm_flags;
+
+ if (vm_flags & (VM_IO | VM_PFNMAP))
+ return -EFAULT;
+
+ if (gup_flags & FOLL_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)) {
+ WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
+ 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;
+ }
+ return 0;
+}
+
/**
* __get_user_pages() - pin user pages in memory
* @tsk: task_struct of target task
@@ -369,9 +407,9 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *nonblocking)
{
- long i;
- unsigned long vm_flags;
+ long i = 0;
unsigned int page_mask;
+ struct vm_area_struct *vma = NULL;
if (!nr_pages)
return 0;
@@ -390,124 +428,82 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
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)) {
- int ret;
- ret = get_gate_page(mm, start & PAGE_MASK, gup_flags,
- &vma, pages ? &pages[i] : NULL);
- if (ret)
- goto efault;
- page_mask = 0;
- goto next_page;
- }
+ 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)) {
+ int ret;
+ ret = get_gate_page(mm, start & PAGE_MASK,
+ gup_flags, &vma,
+ pages ? &pages[i] : NULL);
+ if (ret)
+ return i ? : ret;
+ 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;
- }
+ if (!vma || check_vma_flags(vma, gup_flags))
+ return i ? : -EFAULT;
+ if (is_vm_hugetlb_page(vma)) {
+ i = follow_hugetlb_page(mm, vma, pages, vmas,
+ &start, &nr_pages, i,
+ gup_flags);
+ continue;
}
- } 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;
+ }
+retry:
+ /*
+ * 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();
+ page = follow_page_mask(vma, start, foll_flags, &page_mask);
+ if (!page) {
+ int ret;
+ ret = faultin_page(tsk, vma, start, &foll_flags,
+ nonblocking);
+ switch (ret) {
+ case 0:
+ goto retry;
+ case -EFAULT:
+ case -ENOMEM:
+ case -EHWPOISON:
+ return i ? i : ret;
+ case -EBUSY:
+ return i;
+ case -ENOENT:
+ goto next_page;
}
+ BUG();
}
-
- if (is_vm_hugetlb_page(vma)) {
- i = follow_hugetlb_page(mm, vma, pages, vmas,
- &start, &nr_pages, i, gup_flags);
- continue;
+ 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;
}
-
- 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;
- ret = faultin_page(tsk, vma, start, &foll_flags,
- nonblocking);
- switch (ret) {
- case 0:
- break;
- case -EFAULT:
- case -ENOMEM:
- case -EHWPOISON:
- return i ? i : ret;
- case -EBUSY:
- return i;
- case -ENOENT:
- goto next_page;
- default:
- BUG();
- }
- 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);
+ 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);
return i;
-efault:
- return i ? : -EFAULT;
}
EXPORT_SYMBOL(__get_user_pages);
--
1.9.2
--
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the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply related [flat|nested] 6+ messages in thread