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;
 }