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-rw-r--r--mm/internal.h3
-rw-r--r--mm/mlock.c111
2 files changed, 91 insertions, 23 deletions
diff --git a/mm/internal.h b/mm/internal.h
index a43d79335c16..b3f0dd3ffba2 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -412,7 +412,8 @@ void mlock_page(struct page *page);
static inline void mlock_vma_page(struct page *page,
struct vm_area_struct *vma, bool compound)
{
- if (unlikely(vma->vm_flags & VM_LOCKED) &&
+ /* VM_IO check prevents migration from double-counting during mlock */
+ if (unlikely((vma->vm_flags & (VM_LOCKED|VM_IO)) == VM_LOCKED) &&
(compound || !PageTransCompound(page)))
mlock_page(page);
}
diff --git a/mm/mlock.c b/mm/mlock.c
index f8a3a54687dd..581ea8bf1b83 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -14,6 +14,7 @@
#include <linux/swapops.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
+#include <linux/pagewalk.h>
#include <linux/mempolicy.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
@@ -127,25 +128,91 @@ out:
unlock_page_memcg(page);
}
+static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
+ unsigned long end, struct mm_walk *walk)
+
+{
+ struct vm_area_struct *vma = walk->vma;
+ spinlock_t *ptl;
+ pte_t *start_pte, *pte;
+ struct page *page;
+
+ ptl = pmd_trans_huge_lock(pmd, vma);
+ if (ptl) {
+ if (!pmd_present(*pmd))
+ goto out;
+ if (is_huge_zero_pmd(*pmd))
+ goto out;
+ page = pmd_page(*pmd);
+ if (vma->vm_flags & VM_LOCKED)
+ mlock_page(page);
+ else
+ munlock_page(page);
+ goto out;
+ }
+
+ start_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+ for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {
+ if (!pte_present(*pte))
+ continue;
+ page = vm_normal_page(vma, addr, *pte);
+ if (!page)
+ continue;
+ if (PageTransCompound(page))
+ continue;
+ if (vma->vm_flags & VM_LOCKED)
+ mlock_page(page);
+ else
+ munlock_page(page);
+ }
+ pte_unmap(start_pte);
+out:
+ spin_unlock(ptl);
+ cond_resched();
+ return 0;
+}
+
/*
- * munlock_vma_pages_range() - munlock all pages in the vma range.'
- * @vma - vma containing range to be munlock()ed.
+ * mlock_vma_pages_range() - mlock any pages already in the range,
+ * or munlock all pages in the range.
+ * @vma - vma containing range to be mlock()ed or munlock()ed
* @start - start address in @vma of the range
- * @end - end of range in @vma.
- *
- * For mremap(), munmap() and exit().
+ * @end - end of range in @vma
+ * @newflags - the new set of flags for @vma.
*
- * Called with @vma VM_LOCKED.
- *
- * Returns with VM_LOCKED cleared. Callers must be prepared to
- * deal with this.
+ * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED;
+ * called for munlock() and munlockall(), to clear VM_LOCKED from @vma.
*/
-static void munlock_vma_pages_range(struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
+static void mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end, vm_flags_t newflags)
{
- vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+ static const struct mm_walk_ops mlock_walk_ops = {
+ .pmd_entry = mlock_pte_range,
+ };
- /* Reimplementation to follow in later commit */
+ /*
+ * There is a slight chance that concurrent page migration,
+ * or page reclaim finding a page of this now-VM_LOCKED vma,
+ * will call mlock_vma_page() and raise page's mlock_count:
+ * double counting, leaving the page unevictable indefinitely.
+ * Communicate this danger to mlock_vma_page() with VM_IO,
+ * which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas.
+ * mmap_lock is held in write mode here, so this weird
+ * combination should not be visible to other mmap_lock users;
+ * but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED.
+ */
+ if (newflags & VM_LOCKED)
+ newflags |= VM_IO;
+ WRITE_ONCE(vma->vm_flags, newflags);
+
+ lru_add_drain();
+ walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL);
+ lru_add_drain();
+
+ if (newflags & VM_IO) {
+ newflags &= ~VM_IO;
+ WRITE_ONCE(vma->vm_flags, newflags);
+ }
}
/*
@@ -164,10 +231,9 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
pgoff_t pgoff;
int nr_pages;
int ret = 0;
- int lock = !!(newflags & VM_LOCKED);
- vm_flags_t old_flags = vma->vm_flags;
+ vm_flags_t oldflags = vma->vm_flags;
- if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
+ if (newflags == oldflags || (oldflags & VM_SPECIAL) ||
is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
vma_is_dax(vma) || vma_is_secretmem(vma))
/* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
@@ -199,9 +265,9 @@ success:
* Keep track of amount of locked VM.
*/
nr_pages = (end - start) >> PAGE_SHIFT;
- if (!lock)
+ if (!(newflags & VM_LOCKED))
nr_pages = -nr_pages;
- else if (old_flags & VM_LOCKED)
+ else if (oldflags & VM_LOCKED)
nr_pages = 0;
mm->locked_vm += nr_pages;
@@ -211,11 +277,12 @@ success:
* set VM_LOCKED, populate_vma_page_range will bring it back.
*/
- if (lock)
+ if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
+ /* No work to do, and mlocking twice would be wrong */
vma->vm_flags = newflags;
- else
- munlock_vma_pages_range(vma, start, end);
-
+ } else {
+ mlock_vma_pages_range(vma, start, end, newflags);
+ }
out:
*prev = vma;
return ret;