releases/3.10.34/mm-compaction-break-out-of-loop-on-pagebuddy-in-isolate_freepages_block.patch

   1 From 2af120bc040c5ebcda156df6be6a66610ab6957f Mon Sep 17 00:00:00 2001
   2 From: Laura Abbott <lauraa@codeaurora.org>
   3 Date: Mon, 10 Mar 2014 15:49:44 -0700
   4 Subject: mm/compaction: break out of loop on !PageBuddy in isolate_freepages_block
   5
   6 From: Laura Abbott <lauraa@codeaurora.org>
   7
   8 commit 2af120bc040c5ebcda156df6be6a66610ab6957f upstream.
   9
  10 We received several reports of bad page state when freeing CMA pages
  11 previously allocated with alloc_contig_range:
  12
  13     BUG: Bad page state in process Binder_A  pfn:63202
  14     page:d21130b0 count:0 mapcount:1 mapping:  (null) index:0x7dfbf
  15     page flags: 0x40080068(uptodate|lru|active|swapbacked)
  16
  17 Based on the page state, it looks like the page was still in use.  The
  18 page flags do not make sense for the use case though.  Further debugging
  19 showed that despite alloc_contig_range returning success, at least one
  20 page in the range still remained in the buddy allocator.
  21
  22 There is an issue with isolate_freepages_block.  In strict mode (which
  23 CMA uses), if any pages in the range cannot be isolated,
  24 isolate_freepages_block should return failure 0.  The current check
  25 keeps track of the total number of isolated pages and compares against
  26 the size of the range:
  27
  28         if (strict && nr_strict_required > total_isolated)
  29                 total_isolated = 0;
  30
  31 After taking the zone lock, if one of the pages in the range is not in
  32 the buddy allocator, we continue through the loop and do not increment
  33 total_isolated.  If in the last iteration of the loop we isolate more
  34 than one page (e.g.  last page needed is a higher order page), the check
  35 for total_isolated may pass and we fail to detect that a page was
  36 skipped.  The fix is to bail out if the loop immediately if we are in
  37 strict mode.  There's no benfit to continuing anyway since we need all
  38 pages to be isolated.  Additionally, drop the error checking based on
  39 nr_strict_required and just check the pfn ranges.  This matches with
  40 what isolate_freepages_range does.
  41
  42 Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
  43 Acked-by: Minchan Kim <minchan@kernel.org>
  44 Cc: Mel Gorman <mgorman@suse.de>
  45 Acked-by: Vlastimil Babka <vbabka@suse.cz>
  46 Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
  47 Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
  48 Acked-by: Michal Nazarewicz <mina86@mina86.com>
  49 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  50 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  51 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  52
  53 ---
  54  mm/compaction.c |   20 +++++++++++++-------
  55  1 file changed, 13 insertions(+), 7 deletions(-)
  56
  57 --- a/mm/compaction.c
  58 +++ b/mm/compaction.c
  59 @@ -252,7 +252,6 @@ static unsigned long isolate_freepages_b
  60  {
  61         int nr_scanned = 0, total_isolated = 0;
  62         struct page *cursor, *valid_page = NULL;
  63 -       unsigned long nr_strict_required = end_pfn - blockpfn;
  64         unsigned long flags;
  65         bool locked = false;
  66
  67 @@ -265,11 +264,12 @@ static unsigned long isolate_freepages_b
  68
  69                 nr_scanned++;
  70                 if (!pfn_valid_within(blockpfn))
  71 -                       continue;
  72 +                       goto isolate_fail;
  73 +
  74                 if (!valid_page)
  75                         valid_page = page;
  76                 if (!PageBuddy(page))
  77 -                       continue;
  78 +                       goto isolate_fail;
  79
  80                 /*
  81                  * The zone lock must be held to isolate freepages.
  82 @@ -290,12 +290,10 @@ static unsigned long isolate_freepages_b
  83
  84                 /* Recheck this is a buddy page under lock */
  85                 if (!PageBuddy(page))
  86 -                       continue;
  87 +                       goto isolate_fail;
  88
  89                 /* Found a free page, break it into order-0 pages */
  90                 isolated = split_free_page(page);
  91 -               if (!isolated && strict)
  92 -                       break;
  93                 total_isolated += isolated;
  94                 for (i = 0; i < isolated; i++) {
  95                         list_add(&page->lru, freelist);
  96 @@ -306,7 +304,15 @@ static unsigned long isolate_freepages_b
  97                 if (isolated) {
  98                         blockpfn += isolated - 1;
  99                         cursor += isolated - 1;
 100 +                       continue;
 101                 }
 102 +
 103 +isolate_fail:
 104 +               if (strict)
 105 +                       break;
 106 +               else
 107 +                       continue;
 108 +
 109         }
 110
 111         trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
 112 @@ -316,7 +322,7 @@ static unsigned long isolate_freepages_b
 113          * pages requested were isolated. If there were any failures, 0 is
 114          * returned and CMA will fail.
 115          */
 116 -       if (strict && nr_strict_required > total_isolated)
 117 +       if (strict && blockpfn < end_pfn)
 118                 total_isolated = 0;
 119
 120         if (locked)