| Message ID | 1468515565-81313-1-git-send-email-vsementsov@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/14/2016 10:59 AM, Vladimir Sementsov-Ogievskiy wrote: > There are no needs to allocate more than one cluster, as we set > avail_out for deflate to one cluster. > > Zlib docs (http://www.zlib.net/manual.html) says: > "deflate compresses as much data as possible, and stops when the input > buffer becomes empty or the output buffer becomes full." > > So, deflate will not write more than avail_out to output buffer. If > there is no enough space in output buffer for compressed data (it may be s/no/not/ > larger than input data) deflate just returns Z_OK. (if all data is > compressed and written to output buffer deflate returns Z_STREAM_END). > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> > --- Reviewed-by: Eric Blake <eblake@redhat.com>
On 07/14/2016 12:59 PM, Vladimir Sementsov-Ogievskiy wrote: > There are no needs to allocate more than one cluster, as we set > avail_out for deflate to one cluster. > > Zlib docs (http://www.zlib.net/manual.html) says: > "deflate compresses as much data as possible, and stops when the input > buffer becomes empty or the output buffer becomes full." > > So, deflate will not write more than avail_out to output buffer. If > there is no enough space in output buffer for compressed data (it may be > larger than input data) deflate just returns Z_OK. (if all data is > compressed and written to output buffer deflate returns Z_STREAM_END). > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> > --- > > v2: improve commit message > > block/qcow.c | 2 +- > block/qcow2.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/qcow.c b/block/qcow.c > index ac849bd..d8826f3 100644 > --- a/block/qcow.c > +++ b/block/qcow.c > @@ -983,7 +983,7 @@ static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num, > return ret; > } > > - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); > + out_buf = g_malloc(s->cluster_size); > > /* best compression, small window, no zlib header */ > memset(&strm, 0, sizeof(strm)); > diff --git a/block/qcow2.c b/block/qcow2.c > index a5ea19b..b1c90ae 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -2612,7 +2612,7 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num, > return ret; > } > > - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); > + out_buf = g_malloc(s->cluster_size); > > /* best compression, small window, no zlib header */ > memset(&strm, 0, sizeof(strm)); > Reviewed-by: John Snow <jsnow@redhat.com>
On 14.07.2016 18:59, Vladimir Sementsov-Ogievskiy wrote: > There are no needs to allocate more than one cluster, as we set > avail_out for deflate to one cluster. > > Zlib docs (http://www.zlib.net/manual.html) says: > "deflate compresses as much data as possible, and stops when the input > buffer becomes empty or the output buffer becomes full." > > So, deflate will not write more than avail_out to output buffer. If > there is no enough space in output buffer for compressed data (it may be > larger than input data) deflate just returns Z_OK. (if all data is > compressed and written to output buffer deflate returns Z_STREAM_END). > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> > --- > > v2: improve commit message > > block/qcow.c | 2 +- > block/qcow2.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) Thanks Vladimir, applied to my block branch (with s/no/not/ as proposed by Eric): https://github.com/XanClic/qemu/commits/block Max
diff --git a/block/qcow.c b/block/qcow.c index ac849bd..d8826f3 100644 --- a/block/qcow.c +++ b/block/qcow.c @@ -983,7 +983,7 @@ static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num, return ret; } - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); + out_buf = g_malloc(s->cluster_size); /* best compression, small window, no zlib header */ memset(&strm, 0, sizeof(strm)); diff --git a/block/qcow2.c b/block/qcow2.c index a5ea19b..b1c90ae 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2612,7 +2612,7 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num, return ret; } - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); + out_buf = g_malloc(s->cluster_size); /* best compression, small window, no zlib header */ memset(&strm, 0, sizeof(strm));
There are no needs to allocate more than one cluster, as we set avail_out for deflate to one cluster. Zlib docs (http://www.zlib.net/manual.html) says: "deflate compresses as much data as possible, and stops when the input buffer becomes empty or the output buffer becomes full." So, deflate will not write more than avail_out to output buffer. If there is no enough space in output buffer for compressed data (it may be larger than input data) deflate just returns Z_OK. (if all data is compressed and written to output buffer deflate returns Z_STREAM_END). Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> --- v2: improve commit message block/qcow.c | 2 +- block/qcow2.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)