On Sun, Dec 23, 2018 at 10:59:39AM +0800, yuchenlin wrote: > The dmg file has many tables which describe: "start from sector XXX to > sector XXX, the compression method is XXX and where the compressed data > resides on". > > Each sector in the expanded file should be covered by a table. The table > will describe the offset of compressed data (or raw depends on the type) > in the dmg. > > For example: > > [-----------The expanded file------------] > [---bzip table ---]/* zeros */[---zlib---] > ^ > | if we want to read this sector. > > we will find bzip table which contains this sector, and get the > compressed data offset, read it from dmg, uncompress it, finally write to > expanded file. > > If we skip zero chunk (table), some sector cannot find the table which > will cause search_chunk() return s->n_chunks, dmg_read_chunk() return -1 > and finally causing dmg_co_preadv() return EIO. > > See: > > [-----------The expanded file------------] > [---bzip table ---]/* zeros */[---zlib---] > ^ > | if we want to read this sector. > > Oops, we cannot find the table contains it... > > In the original implementation, we don't have zero table. When we try to > read sector inside the zero chunk. We will get EIO, and skip reading. > > After this patch, we treat zero chunk the same as ignore chunk, it will > directly write zero and avoid some sector may not find the table. > > After this patch: > > [-----------The expanded file------------] > [---bzip table ---][--zeros--][---zlib---] > > Signed-off-by: yuchenlin <npes87...@gmail.com> > --- > block/dmg.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
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