lkml.org 
[lkml]   [2019]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 03/12] percpu: introduce helper to determine if two regions overlap
Date
While block hints were always accurate, it's possible when spanning
across blocks that we miss updating the chunk's contig_hint. Rather than
rely on correctness of the boundaries of hints, do a full overlap
comparison.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
mm/percpu.c | 31 +++++++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 69ca51d238b5..b40112b2fc59 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -546,6 +546,24 @@ static inline int pcpu_cnt_pop_pages(struct pcpu_chunk *chunk, int bit_off,
bitmap_weight(chunk->populated, page_start);
}

+/*
+ * pcpu_region_overlap - determines if two regions overlap
+ * @a: start of first region, inclusive
+ * @b: end of first region, exclusive
+ * @x: start of second region, inclusive
+ * @y: end of second region, exclusive
+ *
+ * This is used to determine if the hint region [a, b) overlaps with the
+ * allocated region [x, y).
+ */
+static inline bool pcpu_region_overlap(int a, int b, int x, int y)
+{
+ if ((x >= a && x < b) || (y > a && y <= b) ||
+ (x <= a && y >= b))
+ return true;
+ return false;
+}
+
/**
* pcpu_chunk_update - updates the chunk metadata given a free area
* @chunk: chunk of interest
@@ -710,8 +728,11 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
PCPU_BITMAP_BLOCK_BITS,
s_off + bits);

- if (s_off >= s_block->contig_hint_start &&
- s_off < s_block->contig_hint_start + s_block->contig_hint) {
+ if (pcpu_region_overlap(s_block->contig_hint_start,
+ s_block->contig_hint_start +
+ s_block->contig_hint,
+ s_off,
+ s_off + bits)) {
/* block contig hint is broken - scan to fix it */
pcpu_block_refresh_hint(chunk, s_index);
} else {
@@ -764,8 +785,10 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
* contig hint is broken. Otherwise, it means a smaller space
* was used and therefore the chunk contig hint is still correct.
*/
- if (bit_off >= chunk->contig_bits_start &&
- bit_off < chunk->contig_bits_start + chunk->contig_bits)
+ if (pcpu_region_overlap(chunk->contig_bits_start,
+ chunk->contig_bits_start + chunk->contig_bits,
+ bit_off,
+ bit_off + bits))
pcpu_chunk_refresh_hint(chunk);
}

--
2.17.1
\
 
 \ /
  Last update: 2019-02-28 03:20    [W:0.191 / U:34.952 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site