memblock, numa: introduce flags field into memblock

[karo-tx-linux.git] / mm / mlock.c

diff --git a/mm/mlock.c b/mm/mlock.c
index d480cd6fc475854259bdd51021d5125dbdfbe479..10819ed4df3e6b34846c01e5cd4de84d5a33fe62 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -133,7 +133,10 @@ static void __munlock_isolation_failed(struct page *page)
 
 /**
  * munlock_vma_page - munlock a vma page
- * @page - page to be unlocked
+ * @page - page to be unlocked, either a normal page or THP page head
+ *
+ * returns the size of the page as a page mask (0 for normal page,
+ *         HPAGE_PMD_NR - 1 for THP head page)
  *
  * called from munlock()/munmap() path with page supposedly on the LRU.
  * When we munlock a page, because the vma where we found the page is being
@@ -148,21 +151,30 @@ static void __munlock_isolation_failed(struct page *page)
  */
 unsigned int munlock_vma_page(struct page *page)
 {
-       unsigned int page_mask = 0;
+       unsigned int nr_pages;
 
        BUG_ON(!PageLocked(page));
 
        if (TestClearPageMlocked(page)) {
-               unsigned int nr_pages = hpage_nr_pages(page);
+               nr_pages = hpage_nr_pages(page);
                mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
-               page_mask = nr_pages - 1;
                if (!isolate_lru_page(page))
                        __munlock_isolated_page(page);
                else
                        __munlock_isolation_failed(page);
+       } else {
+               nr_pages = hpage_nr_pages(page);
        }
 
-       return page_mask;
+       /*
+        * Regardless of the original PageMlocked flag, we determine nr_pages
+        * after touching the flag. This leaves a possible race with a THP page
+        * split, such that a whole THP page was munlocked, but nr_pages == 1.
+        * Returning a smaller mask due to that is OK, the worst that can
+        * happen is subsequent useless scanning of the former tail pages.
+        * The NR_MLOCK accounting can however become broken.
+        */
+       return nr_pages - 1;
 }
 
 /**
@@ -286,10 +298,12 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
 {
        int i;
        int nr = pagevec_count(pvec);
-       int delta_munlocked = -nr;
+       int delta_munlocked;
        struct pagevec pvec_putback;
        int pgrescued = 0;
 
+       pagevec_init(&pvec_putback, 0);
+
        /* Phase 1: page isolation */
        spin_lock_irq(&zone->lru_lock);
        for (i = 0; i < nr; i++) {
@@ -318,18 +332,21 @@ skip_munlock:
                        /*
                         * We won't be munlocking this page in the next phase
                         * but we still need to release the follow_page_mask()
-                        * pin.
+                        * pin. We cannot do it under lru_lock however. If it's
+                        * the last pin, __page_cache_release would deadlock.
                         */
+                       pagevec_add(&pvec_putback, pvec->pages[i]);
                        pvec->pages[i] = NULL;
-                       put_page(page);
-                       delta_munlocked++;
                }
        }
+       delta_munlocked = -nr + pagevec_count(&pvec_putback);
        __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
        spin_unlock_irq(&zone->lru_lock);
 
+       /* Now we can release pins of pages that we are not munlocking */
+       pagevec_release(&pvec_putback);
+
        /* Phase 2: page munlock */
-       pagevec_init(&pvec_putback, 0);
        for (i = 0; i < nr; i++) {
                struct page *page = pvec->pages[i];
 
@@ -440,7 +457,8 @@ void munlock_vma_pages_range(struct vm_area_struct *vma,
 
        while (start < end) {
                struct page *page = NULL;
-               unsigned int page_mask, page_increm;
+               unsigned int page_mask;
+               unsigned long page_increm;
                struct pagevec pvec;
                struct zone *zone;
                int zoneid;
@@ -490,7 +508,9 @@ void munlock_vma_pages_range(struct vm_area_struct *vma,
                                goto next;
                        }
                }
-               page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
+               /* It's a bug to munlock in the middle of a THP page */
+               VM_BUG_ON((start >> PAGE_SHIFT) & page_mask);
+               page_increm = 1 + page_mask;
                start += page_increm * PAGE_SIZE;
 next:
                cond_resched();
@@ -689,19 +709,21 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 
        lru_add_drain_all();    /* flush pagevec */
 
-       down_write(&current->mm->mmap_sem);
        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
        start &= PAGE_MASK;
 
-       locked = len >> PAGE_SHIFT;
-       locked += current->mm->locked_vm;
-
        lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
+       locked = len >> PAGE_SHIFT;
+
+       down_write(&current->mm->mmap_sem);
+
+       locked += current->mm->locked_vm;
 
        /* check against resource limits */
        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
                error = do_mlock(start, len, 1);
+
        up_write(&current->mm->mmap_sem);
        if (!error)
                error = __mm_populate(start, len, 0);
@@ -712,11 +734,13 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 {
        int ret;
 
-       down_write(&current->mm->mmap_sem);
        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
        start &= PAGE_MASK;
+
+       down_write(&current->mm->mmap_sem);
        ret = do_mlock(start, len, 0);
        up_write(&current->mm->mmap_sem);
+
        return ret;
 }
 
@@ -761,12 +785,12 @@ SYSCALL_DEFINE1(mlockall, int, flags)
        if (flags & MCL_CURRENT)
                lru_add_drain_all();    /* flush pagevec */
 
-       down_write(&current->mm->mmap_sem);
-
        lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
 
        ret = -ENOMEM;
+       down_write(&current->mm->mmap_sem);
+
        if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
            capable(CAP_IPC_LOCK))
                ret = do_mlockall(flags);