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From: | Julio Faracco |
Subject: | Re: [Qemu-block] [Qemu-devel] [PATCH v2 1/3] dmg: fix binary search |
Date: | Mon, 24 Dec 2018 13:27:38 -0200 |
There is a possible hang in original binary search implementation. That is
if chunk1 = 4, chunk2 = 5, chunk3 = 4, and we go else case.
The chunk1 will be still 4, and so on.
Signed-off-by: yuchenlin <address@hidden>
---
block/dmg.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/block/dmg.c b/block/dmg.c
index 50e91aef6d..0e05702f5d 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -572,14 +572,14 @@ static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
{
/* binary search */
uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
- while (chunk1 != chunk2) {
+ while (chunk1 <= chunk2) {
chunk3 = (chunk1 + chunk2) / 2;
if (s->sectors[chunk3] > sector_num) {
- chunk2 = chunk3;
+ chunk2 = chunk3 - 1;
} else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
return chunk3;
} else {
- chunk1 = chunk3;
+ chunk1 = chunk3 + 1;
}
}
return s->n_chunks; /* error */
--
2.17.1
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