Commit 20fbb34e authored by Yue Hu's avatar Yue Hu Committed by Greg Kroah-Hartman

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

[ Upstream commit 2b59e01a3aa665f751d1410b99fae9336bd424e1 ]

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: default avatarYue Hu <>
Reviewed-by: default avatarAndrew Morton <>
Cc: Joonsoo Kim <>
Cc: Ingo Molnar <>
Cc: Vlastimil Babka <>
Cc: Mike Rapoport <>
Cc: Randy Dunlap <>
Cc: Laura Abbott <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
Signed-off-by: default avatarSasha Levin <>
parent f3da1dc8
......@@ -366,23 +366,26 @@ int __init cma_declare_contiguous(phys_addr_t base,
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);
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)
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,
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);
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