Commit 5ef40828 authored by yuchenlin's avatar yuchenlin Committed by Stefan Hajnoczi
Browse files

dmg: fix binary search 



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: default avataryuchenlin <npes87184@gmail.com>
Message-id: 20190103114700.9686-2-npes87184@gmail.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent b47c7d53

block/dmg.c

+7 −3
Original line number Diff line number Diff line
@@ -572,16 +572,20 @@ 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;

            if (chunk3 == 0) {

                goto err;

            }

            chunk2 = chunk3 - 1;

        } else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {

            return chunk3;

        } else {

            chunk1 = chunk3;

            chunk1 = chunk3 + 1;

        }

    }

err:

    return s->n_chunks; /* error */

}