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author | Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> | 2018-06-20 17:48:36 +0300 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2018-07-05 10:29:00 +0200 |
commit | 2714f13d69adf73638842729ccfb3bdd6d5ee98f (patch) | |
tree | bffa272114f2b264f94cb8f05c3509f0eaf2c1b1 /block | |
parent | 88481329c0a43373f994f0c8ed19e888a8c86830 (diff) | |
download | qemu-2714f13d69adf73638842729ccfb3bdd6d5ee98f.zip qemu-2714f13d69adf73638842729ccfb3bdd6d5ee98f.tar.gz qemu-2714f13d69adf73638842729ccfb3bdd6d5ee98f.tar.bz2 |
qcow2: refactor data compression
Make a separate function for compression to be parallelized later.
- use .avail_out field instead of .next_out to calculate size of
compressed data. It looks more natural and it allows to keep dest to
be void pointer
- set avail_out to be at least one byte less than input, to be sure
avoid inefficient compression earlier
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/qcow2.c | 78 |
1 files changed, 51 insertions, 27 deletions
diff --git a/block/qcow2.c b/block/qcow2.c index 2f9e58e..9cee653 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -23,11 +23,14 @@ */ #include "qemu/osdep.h" + +#define ZLIB_CONST +#include <zlib.h> + #include "block/block_int.h" #include "block/qdict.h" #include "sysemu/block-backend.h" #include "qemu/module.h" -#include <zlib.h> #include "qcow2.h" #include "qemu/error-report.h" #include "qapi/error.h" @@ -3650,6 +3653,48 @@ fail: return ret; } +/* + * qcow2_compress() + * + * @dest - destination buffer, at least of @size-1 bytes + * @src - source buffer, @size bytes + * + * Returns: compressed size on success + * -1 if compression is inefficient + * -2 on any other error + */ +static ssize_t qcow2_compress(void *dest, const void *src, size_t size) +{ + ssize_t ret; + z_stream strm; + + /* best compression, small window, no zlib header */ + memset(&strm, 0, sizeof(strm)); + ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, + -12, 9, Z_DEFAULT_STRATEGY); + if (ret != 0) { + return -2; + } + + /* strm.next_in is not const in old zlib versions, such as those used on + * OpenBSD/NetBSD, so cast the const away */ + strm.avail_in = size; + strm.next_in = (void *) src; + strm.avail_out = size - 1; + strm.next_out = dest; + + ret = deflate(&strm, Z_FINISH); + if (ret == Z_STREAM_END) { + ret = size - 1 - strm.avail_out; + } else { + ret = (ret == Z_OK ? -1 : -2); + } + + deflateEnd(&strm); + + return ret; +} + /* XXX: put compressed sectors first, then all the cluster aligned tables to avoid losing bytes in alignment */ static coroutine_fn int @@ -3659,8 +3704,8 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset, BDRVQcow2State *s = bs->opaque; QEMUIOVector hd_qiov; struct iovec iov; - z_stream strm; - int ret, out_len; + int ret; + size_t out_len; uint8_t *buf, *out_buf; int64_t cluster_offset; @@ -3694,32 +3739,11 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset, out_buf = g_malloc(s->cluster_size); - /* best compression, small window, no zlib header */ - memset(&strm, 0, sizeof(strm)); - ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION, - Z_DEFLATED, -12, - 9, Z_DEFAULT_STRATEGY); - if (ret != 0) { + out_len = qcow2_compress(out_buf, buf, s->cluster_size); + if (out_len == -2) { ret = -EINVAL; goto fail; - } - - strm.avail_in = s->cluster_size; - strm.next_in = (uint8_t *)buf; - strm.avail_out = s->cluster_size; - strm.next_out = out_buf; - - ret = deflate(&strm, Z_FINISH); - if (ret != Z_STREAM_END && ret != Z_OK) { - deflateEnd(&strm); - ret = -EINVAL; - goto fail; - } - out_len = strm.next_out - out_buf; - - deflateEnd(&strm); - - if (ret != Z_STREAM_END || out_len >= s->cluster_size) { + } else if (out_len == -1) { /* could not compress: write normal cluster */ ret = qcow2_co_pwritev(bs, offset, bytes, qiov, 0); if (ret < 0) { |