Merge branch 'akpm' (patches from Andrew)

Merge updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - the v9fs maintainers have been missing for a long time. I've taken
   over v9fs patch slinging.

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (116 commits)
  mm,oom_reaper: check for MMF_OOM_SKIP before complaining
  mm/ksm: fix interaction with THP
  mm/memblock.c: cast constant ULLONG_MAX to phys_addr_t
  headers: untangle kmemleak.h from mm.h
  include/linux/mmdebug.h: make VM_WARN* non-rvals
  mm/page_isolation.c: make start_isolate_page_range() fail if already isolated
  mm: change return type to vm_fault_t
  mm, oom: remove 3% bonus for CAP_SYS_ADMIN processes
  mm, page_alloc: wakeup kcompactd even if kswapd cannot free more memory
  kernel/fork.c: detect early free of a live mm
  mm: make counting of list_lru_one::nr_items lockless
  mm/swap_state.c: make bool enable_vma_readahead and swap_vma_readahead() static
  block_invalidatepage(): only release page if the full page was invalidated
  mm: kernel-doc: add missing parameter descriptions
  mm/swap.c: remove @cold parameter description for release_pages()
  mm/nommu: remove description of alloc_vm_area
  zram: drop max_zpage_size and use zs_huge_class_size()
  zsmalloc: introduce zs_huge_class_size()
  mm: fix races between swapoff and flush dcache
  fs/direct-io.c: minor cleanups in do_blockdev_direct_IO
  ...

1 files changed, 17 insertions, 1 deletions

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 165ed8117bd1..61dee77bb211 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -28,6 +28,14 @@ static int set_migratetype_isolate(struct page *page, int migratetype,
 
 	spin_lock_irqsave(&zone->lock, flags);
 
+	/*
+	 * We assume the caller intended to SET migrate type to isolate.
+	 * If it is already set, then someone else must have raced and
+	 * set it before us.  Return -EBUSY
+	 */
+	if (is_migrate_isolate_page(page))
+		goto out;
+
 	pfn = page_to_pfn(page);
 	arg.start_pfn = pfn;
 	arg.nr_pages = pageblock_nr_pages;
@@ -166,7 +174,15 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
  * future will not be allocated again.
  *
  * start_pfn/end_pfn must be aligned to pageblock_order.
- * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
+ * Return 0 on success and -EBUSY if any part of range cannot be isolated.
+ *
+ * There is no high level synchronization mechanism that prevents two threads
+ * from trying to isolate overlapping ranges.  If this happens, one thread
+ * will notice pageblocks in the overlapping range already set to isolate.
+ * This happens in set_migratetype_isolate, and set_migratetype_isolate
+ * returns an error.  We then clean up by restoring the migration type on
+ * pageblocks we may have modified and return -EBUSY to caller.  This
+ * prevents two threads from simultaneously working on overlapping ranges.
  */
 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 			     unsigned migratetype, bool skip_hwpoisoned_pages)