queue-4.19/mm-cma.c-fix-the-bitmap-status-to-show-failed-alloca.patch

   1 From 9da1b4ca02dcc2d7059c9f615dcd317d8fb28dd0 Mon Sep 17 00:00:00 2001
   2 From: Yue Hu <huyue2@yulong.com>
   3 Date: Mon, 13 May 2019 17:17:41 -0700
   4 Subject: mm/cma.c: fix the bitmap status to show failed allocation reason
   5
   6 [ Upstream commit 2b59e01a3aa665f751d1410b99fae9336bd424e1 ]
   7
   8 Currently one bit in cma bitmap represents number of pages rather than
   9 one page, cma->count means cma size in pages. So to find available pages
  10 via find_next_zero_bit()/find_next_bit() we should use cma size not in
  11 pages but in bits although current free pages number is correct due to
  12 zero value of order_per_bit. Once order_per_bit is changed the bitmap
  13 status will be incorrect.
  14
  15 The size input in cma_debug_show_areas() is not correct.  It will
  16 affect the available pages at some position to debug the failure issue.
  17
  18 This is an example with order_per_bit = 1
  19
  20 Before this change:
  21 [    4.120060] cma: number of available pages: 1@93+4@108+7@121+7@137+7@153+7@169+7@185+7@201+3@213+3@221+3@229+3@237+3@245+3@253+3@261+3@269+3@277+3@285+3@293+3@301+3@309+3@317+3@325+19@333+15@369+512@512=> 638 free of 1024 total pages
  22
  23 After this change:
  24 [    4.143234] cma: number of available pages: 2@93+8@108+14@121+14@137+14@153+14@169+14@185+14@201+6@213+6@221+6@229+6@237+6@245+6@253+6@261+6@269+6@277+6@285+6@293+6@301+6@309+6@317+6@325+38@333+30@369=> 252 free of 1024 total pages
  25
  26 Obviously the bitmap status before is incorrect.
  27
  28 Link: http://lkml.kernel.org/r/20190320060829.9144-1-zbestahu@gmail.com
  29 Signed-off-by: Yue Hu <huyue2@yulong.com>
  30 Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
  31 Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
  32 Cc: Ingo Molnar <mingo@kernel.org>
  33 Cc: Vlastimil Babka <vbabka@suse.cz>
  34 Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
  35 Cc: Randy Dunlap <rdunlap@infradead.org>
  36 Cc: Laura Abbott <labbott@redhat.com>
  37 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  38 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  39 Signed-off-by: Sasha Levin <sashal@kernel.org>
  40 ---
  41  mm/cma.c | 19 +++++++++++--------
  42  1 file changed, 11 insertions(+), 8 deletions(-)
  43
  44 diff --git a/mm/cma.c b/mm/cma.c
  45 index 6ce6e22f82d9..476dfe13a701 100644
  46 --- a/mm/cma.c
  47 +++ b/mm/cma.c
  48 @@ -371,23 +371,26 @@ err:
  49  #ifdef CONFIG_CMA_DEBUG
  50  static void cma_debug_show_areas(struct cma *cma)
  51  {
  52 -       unsigned long next_zero_bit, next_set_bit;
  53 +       unsigned long next_zero_bit, next_set_bit, nr_zero;
  54         unsigned long start = 0;
  55 -       unsigned int nr_zero, nr_total = 0;
  56 +       unsigned long nr_part, nr_total = 0;
  57 +       unsigned long nbits = cma_bitmap_maxno(cma);
  58
  59         mutex_lock(&cma->lock);
  60         pr_info("number of available pages: ");
  61         for (;;) {
  62 -               next_zero_bit = find_next_zero_bit(cma->bitmap, cma->count, start);
  63 -               if (next_zero_bit >= cma->count)
  64 +               next_zero_bit = find_next_zero_bit(cma->bitmap, nbits, start);
  65 +               if (next_zero_bit >= nbits)
  66                         break;
  67 -               next_set_bit = find_next_bit(cma->bitmap, cma->count, next_zero_bit);
  68 +               next_set_bit = find_next_bit(cma->bitmap, nbits, next_zero_bit);
  69                 nr_zero = next_set_bit - next_zero_bit;
  70 -               pr_cont("%s%u@%lu", nr_total ? "+" : "", nr_zero, next_zero_bit);
  71 -               nr_total += nr_zero;
  72 +               nr_part = nr_zero << cma->order_per_bit;
  73 +               pr_cont("%s%lu@%lu", nr_total ? "+" : "", nr_part,
  74 +                       next_zero_bit);
  75 +               nr_total += nr_part;
  76                 start = next_zero_bit + nr_zero;
  77         }
  78 -       pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count);
  79 +       pr_cont("=> %lu free of %lu total pages\n", nr_total, cma->count);
  80         mutex_unlock(&cma->lock);
  81  }
  82  #else
  83 --
  84 2.20.1
  85