mm/cma.c: fix the bitmap status to show failed allocation reason

Currently one bit in cma bitmap represents number of pages rather than
one page, cma->count means cma size in pages. So to find available pages
via find_next_zero_bit()/find_next_bit() we should use cma size not in
pages but in bits although current free pages number is correct due to
zero value of order_per_bit. Once order_per_bit is changed the bitmap
status will be incorrect.

The size input in cma_debug_show_areas() is not correct.  It will
affect the available pages at some position to debug the failure issue.

This is an example with order_per_bit = 1

Before this change:
[    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

After this change:
[    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

Obviously the bitmap status before is incorrect.

Link: http://lkml.kernel.org/r/20190320060829.9144-1-zbestahu@gmail.com
Signed-off-by: Yue Hu <huyue2@yulong.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Laura Abbott <labbott@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/cma.c b/mm/cma.c
index bb2d333..d72a02f 100644 (file)
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -367,23 +367,26 @@ err:
 #ifdef CONFIG_CMA_DEBUG
 static void cma_debug_show_areas(struct cma *cma)
 {
-       unsigned long next_zero_bit, next_set_bit;
+       unsigned long next_zero_bit, next_set_bit, nr_zero;
        unsigned long start = 0;
-       unsigned int nr_zero, nr_total = 0;
+       unsigned long nr_part, nr_total = 0;
+       unsigned long nbits = cma_bitmap_maxno(cma);
 
        mutex_lock(&cma->lock);
        pr_info("number of available pages: ");
        for (;;) {
-               next_zero_bit = find_next_zero_bit(cma->bitmap, cma->count, start);
-               if (next_zero_bit >= cma->count)
+               next_zero_bit = find_next_zero_bit(cma->bitmap, nbits, start);
+               if (next_zero_bit >= nbits)
                        break;
-               next_set_bit = find_next_bit(cma->bitmap, cma->count, next_zero_bit);
+               next_set_bit = find_next_bit(cma->bitmap, nbits, next_zero_bit);
                nr_zero = next_set_bit - next_zero_bit;
-               pr_cont("%s%u@%lu", nr_total ? "+" : "", nr_zero, next_zero_bit);
-               nr_total += nr_zero;
+               nr_part = nr_zero << cma->order_per_bit;
+               pr_cont("%s%lu@%lu", nr_total ? "+" : "", nr_part,
+                       next_zero_bit);
+               nr_total += nr_part;
                start = next_zero_bit + nr_zero;
        }
-       pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count);
+       pr_cont("=> %lu free of %lu total pages\n", nr_total, cma->count);
        mutex_unlock(&cma->lock);
 }
 #else