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Subject[PATCH AUTOSEL 5.1 019/186] mm/cma.c: fix the bitmap status to show failed allocation reason
Date
From: Yue Hu <huyue2@yulong.com>

[ 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: 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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/cma.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 8cb95cd1193a9..5e36d7418031c 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -369,23 +369,26 @@ 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
--
2.20.1
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