[PATCH] mm/cma: fix the bitmap status to show failed allocation reason

* [PATCH] mm/cma: fix the bitmap status to show failed allocation reason
@ 2019-03-20  6:08 Yue Hu
  2019-03-20 22:12 ` Andrew Morton
  0 siblings, 1 reply; 4+ messages in thread
From: Yue Hu @ 2019-03-20  6:08 UTC (permalink / raw)
  To: akpm, iamjoonsoo.kim, mingo, vbabka, rppt, rdunlap; +Cc: linux-mm, huyue2

From: Yue Hu <huyue2@yulong.com>

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.

Signed-off-by: Yue Hu <huyue2@yulong.com>
---
 mm/cma.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 5809bbe..6a7aa05 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -367,23 +367,26 @@ int __init cma_declare_contiguous(phys_addr_t base,
 #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
-- 
1.9.1


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