1 files changed, 425 insertions, 18 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index 01fbe93eff5c..008ea70b7afa 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -8,10 +8,18 @@
 #include <linux/capability.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/pagemap.h>
 #include <linux/mempolicy.h>
 #include <linux/syscalls.h>
 #include <linux/sched.h>
 #include <linux/module.h>
+#include <linux/rmap.h>
+#include <linux/mmzone.h>
+#include <linux/hugetlb.h>
+
+#include "internal.h"
 
 int can_do_mlock(void)
 {
@@ -23,17 +31,381 @@ int can_do_mlock(void)
 }
 EXPORT_SYMBOL(can_do_mlock);
 
+#ifdef CONFIG_UNEVICTABLE_LRU
+/*
+ * Mlocked pages are marked with PageMlocked() flag for efficient testing
+ * in vmscan and, possibly, the fault path; and to support semi-accurate
+ * statistics.
+ *
+ * An mlocked page [PageMlocked(page)] is unevictable.  As such, it will
+ * be placed on the LRU "unevictable" list, rather than the [in]active lists.
+ * The unevictable list is an LRU sibling list to the [in]active lists.
+ * PageUnevictable is set to indicate the unevictable state.
+ *
+ * When lazy mlocking via vmscan, it is important to ensure that the
+ * vma's VM_LOCKED status is not concurrently being modified, otherwise we
+ * may have mlocked a page that is being munlocked. So lazy mlock must take
+ * the mmap_sem for read, and verify that the vma really is locked
+ * (see mm/rmap.c).
+ */
+
+/*
+ *  LRU accounting for clear_page_mlock()
+ */
+void __clear_page_mlock(struct page *page)
+{
+        VM_BUG_ON(!PageLocked(page));
+
+        if (!page->mapping) {   /* truncated ? */
+                return;
+        }
+
+        dec_zone_page_state(page, NR_MLOCK);
+        count_vm_event(UNEVICTABLE_PGCLEARED);
+        if (!isolate_lru_page(page)) {
+                putback_lru_page(page);
+        } else {
+                /*
+                 * Page not on the LRU yet.  Flush all pagevecs and retry.
+                 */
+                lru_add_drain_all();
+                if (!isolate_lru_page(page))
+                        putback_lru_page(page);
+                else if (PageUnevictable(page))
+                        count_vm_event(UNEVICTABLE_PGSTRANDED);
+
+        }
+}
+
+/*
+ * Mark page as mlocked if not already.
+ * If page on LRU, isolate and putback to move to unevictable list.
+ */
+void mlock_vma_page(struct page *page)
+{
+        BUG_ON(!PageLocked(page));
+
+        if (!TestSetPageMlocked(page)) {
+                inc_zone_page_state(page, NR_MLOCK);
+                count_vm_event(UNEVICTABLE_PGMLOCKED);
+                if (!isolate_lru_page(page))
+                        putback_lru_page(page);
+        }
+}
+
+/*
+ * called from munlock()/munmap() path with page supposedly on the LRU.
+ *
+ * Note:  unlike mlock_vma_page(), we can't just clear the PageMlocked
+ * [in try_to_munlock()] and then attempt to isolate the page.  We must
+ * isolate the page to keep others from messing with its unevictable
+ * and mlocked state while trying to munlock.  However, we pre-clear the
+ * mlocked state anyway as we might lose the isolation race and we might
+ * not get another chance to clear PageMlocked.  If we successfully
+ * isolate the page and try_to_munlock() detects other VM_LOCKED vmas
+ * mapping the page, it will restore the PageMlocked state, unless the page
+ * is mapped in a non-linear vma.  So, we go ahead and SetPageMlocked(),
+ * perhaps redundantly.
+ * If we lose the isolation race, and the page is mapped by other VM_LOCKED
+ * vmas, we'll detect this in vmscan--via try_to_munlock() or try_to_unmap()
+ * either of which will restore the PageMlocked state by calling
+ * mlock_vma_page() above, if it can grab the vma's mmap sem.
+ */
+static void munlock_vma_page(struct page *page)
+{
+        BUG_ON(!PageLocked(page));
+
+        if (TestClearPageMlocked(page)) {
+                dec_zone_page_state(page, NR_MLOCK);
+                if (!isolate_lru_page(page)) {
+                        int ret = try_to_munlock(page);
+                        /*
+                         * did try_to_unlock() succeed or punt?
+                         */
+                        if (ret == SWAP_SUCCESS || ret == SWAP_AGAIN)
+                                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+
+                        putback_lru_page(page);
+                } else {
+                        /*
+                         * We lost the race.  let try_to_unmap() deal
+                         * with it.  At least we get the page state and
+                         * mlock stats right.  However, page is still on
+                         * the noreclaim list.  We'll fix that up when
+                         * the page is eventually freed or we scan the
+                         * noreclaim list.
+                         */
+                        if (PageUnevictable(page))
+                                count_vm_event(UNEVICTABLE_PGSTRANDED);
+                        else
+                                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+                }
+        }
+}
+
+/**
+ * __mlock_vma_pages_range() -  mlock/munlock a range of pages in the vma.
+ * @vma:   target vma
+ * @start: start address
+ * @end:   end address
+ * @mlock: 0 indicate munlock, otherwise mlock.
+ *
+ * If @mlock == 0, unlock an mlocked range;
+ * else mlock the range of pages.  This takes care of making the pages present ,
+ * too.
+ *
+ * return 0 on success, negative error code on error.
+ *
+ * vma->vm_mm->mmap_sem must be held for at least read.
+ */
+static long __mlock_vma_pages_range(struct vm_area_struct *vma,
+                                   unsigned long start, unsigned long end,
+                                   int mlock)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        unsigned long addr = start;
+        struct page *pages[16]; /* 16 gives a reasonable batch */
+        int nr_pages = (end - start) / PAGE_SIZE;
+        int ret;
+        int gup_flags = 0;
+
+        VM_BUG_ON(start & ~PAGE_MASK);
+        VM_BUG_ON(end   & ~PAGE_MASK);
+        VM_BUG_ON(start < vma->vm_start);
+        VM_BUG_ON(end   > vma->vm_end);
+        VM_BUG_ON((!rwsem_is_locked(&mm->mmap_sem)) &&
+                  (atomic_read(&mm->mm_users) != 0));
+
+        /*
+         * mlock:   don't page populate if page has PROT_NONE permission.
+         * munlock: the pages always do munlock althrough
+         *          its has PROT_NONE permission.
+         */
+        if (!mlock)
+                gup_flags |= GUP_FLAGS_IGNORE_VMA_PERMISSIONS;
+
+        if (vma->vm_flags & VM_WRITE)
+                gup_flags |= GUP_FLAGS_WRITE;
+
+        lru_add_drain_all();    /* push cached pages to LRU */
+
+        while (nr_pages > 0) {
+                int i;
+
+                cond_resched();
+
+                /*
+                 * get_user_pages makes pages present if we are
+                 * setting mlock. and this extra reference count will
+                 * disable migration of this page.  However, page may
+                 * still be truncated out from under us.
+                 */
+                ret = __get_user_pages(current, mm, addr,
+                                min_t(int, nr_pages, ARRAY_SIZE(pages)),
+                                gup_flags, pages, NULL);
+                /*
+                 * This can happen for, e.g., VM_NONLINEAR regions before
+                 * a page has been allocated and mapped at a given offset,
+                 * or for addresses that map beyond end of a file.
+                 * We'll mlock the the pages if/when they get faulted in.
+                 */
+                if (ret < 0)
+                        break;
+                if (ret == 0) {
+                        /*
+                         * We know the vma is there, so the only time
+                         * we cannot get a single page should be an
+                         * error (ret < 0) case.
+                         */
+                        WARN_ON(1);
+                        break;
+                }
+
+                lru_add_drain();        /* push cached pages to LRU */
+
+                for (i = 0; i < ret; i++) {
+                        struct page *page = pages[i];
+
+                        lock_page(page);
+                        /*
+                         * Because we lock page here and migration is blocked
+                         * by the elevated reference, we need only check for
+                         * page truncation (file-cache only).
+                         */
+                        if (page->mapping) {
+                                if (mlock)
+                                        mlock_vma_page(page);
+                                else
+                                        munlock_vma_page(page);
+                        }
+                        unlock_page(page);
+                        put_page(page);         /* ref from get_user_pages() */
+
+                        /*
+                         * here we assume that get_user_pages() has given us
+                         * a list of virtually contiguous pages.
+                         */
+                        addr += PAGE_SIZE;      /* for next get_user_pages() */
+                        nr_pages--;
+                }
+                ret = 0;
+        }
+
+        lru_add_drain_all();    /* to update stats */
+
+        return ret;     /* count entire vma as locked_vm */
+}
+
+/*
+ * convert get_user_pages() return value to posix mlock() error
+ */
+static int __mlock_posix_error_return(long retval)
+{
+        if (retval == -EFAULT)
+                retval = -ENOMEM;
+        else if (retval == -ENOMEM)
+                retval = -EAGAIN;
+        return retval;
+}
+
+#else /* CONFIG_UNEVICTABLE_LRU */
+
+/*
+ * Just make pages present if VM_LOCKED.  No-op if unlocking.
+ */
+static long __mlock_vma_pages_range(struct vm_area_struct *vma,
+                                   unsigned long start, unsigned long end,
+                                   int mlock)
+{
+        if (mlock && (vma->vm_flags & VM_LOCKED))
+                return make_pages_present(start, end);
+        return 0;
+}
+
+static inline int __mlock_posix_error_return(long retval)
+{
+        return 0;
+}
+
+#endif /* CONFIG_UNEVICTABLE_LRU */
+
+/**
+ * mlock_vma_pages_range() - mlock pages in specified vma range.
+ * @vma - the vma containing the specfied address range
+ * @start - starting address in @vma to mlock
+ * @end   - end address [+1] in @vma to mlock
+ *
+ * For mmap()/mremap()/expansion of mlocked vma.
+ *
+ * return 0 on success for "normal" vmas.
+ *
+ * return number of pages [> 0] to be removed from locked_vm on success
+ * of "special" vmas.
+ *
+ * return negative error if vma spanning @start-@range disappears while
+ * mmap semaphore is dropped.  Unlikely?
+ */
+long mlock_vma_pages_range(struct vm_area_struct *vma,
+                        unsigned long start, unsigned long end)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        int nr_pages = (end - start) / PAGE_SIZE;
+        BUG_ON(!(vma->vm_flags & VM_LOCKED));
+
+        /*
+         * filter unlockable vmas
+         */
+        if (vma->vm_flags & (VM_IO | VM_PFNMAP))
+                goto no_mlock;
+
+        if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
+                        is_vm_hugetlb_page(vma) ||
+                        vma == get_gate_vma(current))) {
+                long error;
+                downgrade_write(&mm->mmap_sem);
+
+                error = __mlock_vma_pages_range(vma, start, end, 1);
+
+                up_read(&mm->mmap_sem);
+                /* vma can change or disappear */
+                down_write(&mm->mmap_sem);
+                vma = find_vma(mm, start);
+                /* non-NULL vma must contain @start, but need to check @end */
+                if (!vma ||  end > vma->vm_end)
+                        return -ENOMEM;
+
+                return 0;       /* hide other errors from mmap(), et al */
+        }
+
+        /*
+         * User mapped kernel pages or huge pages:
+         * make these pages present to populate the ptes, but
+         * fall thru' to reset VM_LOCKED--no need to unlock, and
+         * return nr_pages so these don't get counted against task's
+         * locked limit.  huge pages are already counted against
+         * locked vm limit.
+         */
+        make_pages_present(start, end);
+
+no_mlock:
+        vma->vm_flags &= ~VM_LOCKED;    /* and don't come back! */
+        return nr_pages;                /* error or pages NOT mlocked */
+}
+
+
+/*
+ * munlock_vma_pages_range() - munlock all pages in the vma range.'
+ * @vma - vma containing range to be munlock()ed.
+ * @start - start address in @vma of the range
+ * @end - end of range in @vma.
+ *
+ *  For mremap(), munmap() and exit().
+ *
+ * Called with @vma VM_LOCKED.
+ *
+ * Returns with VM_LOCKED cleared.  Callers must be prepared to
+ * deal with this.
+ *
+ * We don't save and restore VM_LOCKED here because pages are
+ * still on lru.  In unmap path, pages might be scanned by reclaim
+ * and re-mlocked by try_to_{munlock|unmap} before we unmap and
+ * free them.  This will result in freeing mlocked pages.
+ */
+void munlock_vma_pages_range(struct vm_area_struct *vma,
+                           unsigned long start, unsigned long end)
+{
+        vma->vm_flags &= ~VM_LOCKED;
+        __mlock_vma_pages_range(vma, start, end, 0);
+}
+
+/*
+ * mlock_fixup  - handle mlock[all]/munlock[all] requests.
+ *
+ * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
+ * munlock is a no-op.  However, for some special vmas, we go ahead and
+ * populate the ptes via make_pages_present().
+ *
+ * For vmas that pass the filters, merge/split as appropriate.
+ */
 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
         unsigned long start, unsigned long end, unsigned int newflags)
 {
-        struct mm_struct * mm = vma->vm_mm;
+        struct mm_struct *mm = vma->vm_mm;
         pgoff_t pgoff;
-        int pages;
+        int nr_pages;
         int ret = 0;
-
-        if (newflags == vma->vm_flags) {
-                *prev = vma;
-                goto out;
+        int lock = newflags & VM_LOCKED;
+
+        if (newflags == vma->vm_flags ||
+                        (vma->vm_flags & (VM_IO | VM_PFNMAP)))
+                goto out;       /* don't set VM_LOCKED,  don't count */
+
+        if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
+                        is_vm_hugetlb_page(vma) ||
+                        vma == get_gate_vma(current)) {
+                if (lock)
+                        make_pages_present(start, end);
+                goto out;       /* don't set VM_LOCKED,  don't count */
         }
 
         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
@@ -44,8 +416,6 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
                 goto success;
         }
 
-        *prev = vma;
-
         if (start != vma->vm_start) {
                 ret = split_vma(mm, vma, start, 1);
                 if (ret)
@@ -60,24 +430,61 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 
 success:
         /*
+         * Keep track of amount of locked VM.
+         */
+        nr_pages = (end - start) >> PAGE_SHIFT;
+        if (!lock)
+                nr_pages = -nr_pages;
+        mm->locked_vm += nr_pages;
+
+        /*
          * vm_flags is protected by the mmap_sem held in write mode.
          * It's okay if try_to_unmap_one unmaps a page just after we
-         * set VM_LOCKED, make_pages_present below will bring it back.
+         * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
          */
         vma->vm_flags = newflags;
 
-        /*
-         * Keep track of amount of locked VM.
-         */
-        pages = (end - start) >> PAGE_SHIFT;
-        if (newflags & VM_LOCKED) {
-                pages = -pages;
-                if (!(newflags & VM_IO))
-                        ret = make_pages_present(start, end);
+        if (lock) {
+                /*
+                 * mmap_sem is currently held for write.  Downgrade the write
+                 * lock to a read lock so that other faults, mmap scans, ...
+                 * while we fault in all pages.
+                 */
+                downgrade_write(&mm->mmap_sem);
+
+                ret = __mlock_vma_pages_range(vma, start, end, 1);
+
+                /*
+                 * Need to reacquire mmap sem in write mode, as our callers
+                 * expect this.  We have no support for atomically upgrading
+                 * a sem to write, so we need to check for ranges while sem
+                 * is unlocked.
+                 */
+                up_read(&mm->mmap_sem);
+                /* vma can change or disappear */
+                down_write(&mm->mmap_sem);
+                *prev = find_vma(mm, start);
+                /* non-NULL *prev must contain @start, but need to check @end */
+                if (!(*prev) || end > (*prev)->vm_end)
+                        ret = -ENOMEM;
+                else if (ret > 0) {
+                        mm->locked_vm -= ret;
+                        ret = 0;
+                } else
+                        ret = __mlock_posix_error_return(ret); /* translate if needed */
+        } else {
+                /*
+                 * TODO:  for unlocking, pages will already be resident, so
+                 * we don't need to wait for allocations/reclaim/pagein, ...
+                 * However, unlocking a very large region can still take a
+                 * while.  Should we downgrade the semaphore for both lock
+                 * AND unlock ?
+                 */
+                __mlock_vma_pages_range(vma, start, end, 0);
         }
 
-        mm->locked_vm -= pages;
 out:
+        *prev = vma;
         return ret;
 }