[PATCH v8 3/4] qcow2: add zstd cluster compression

[Denis Plotnikov]

zstd significantly reduces cluster compression time.
It provides better compression performance maintaining
the same level of the compression ratio in comparison with
zlib, which, at the moment, is the only compression
method available.

The performance test results:
Test compresses and decompresses qemu qcow2 image with just
installed rhel-7.6 guest.
Image cluster size: 64K. Image on disk size: 2.2G

The test was conducted with brd disk to reduce the influence
of disk subsystem to the test results.
The results is given in seconds.

compress cmd:
  time ./qemu-img convert -O qcow2 -c -o compression_type=[zlib|zstd]
                  src.img [zlib|zstd]_compressed.img
decompress cmd
  time ./qemu-img convert -O qcow2
                  [zlib|zstd]_compressed.img uncompressed.img

           compression               decompression
         zlib       zstd           zlib         zstd
------------------------------------------------------------
real     65.5       16.3 (-75 %)    1.9          1.6 (-16 %)
user     65.0       15.8            5.3          2.5
sys       3.3        0.2            2.0          2.0

Both ZLIB and ZSTD gave the same compression ratio: 1.57
compressed image size in both cases: 1.4G

Signed-off-by: Denis Plotnikov <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Reviewed-by: Alberto Garcia <address@hidden>
QAPI part:
Acked-by: Markus Armbruster <address@hidden>
---
 docs/interop/qcow2.txt |   1 +
 configure              |   2 +-
 qapi/block-core.json   |   3 +-
 block/qcow2-threads.c  | 129 +++++++++++++++++++++++++++++++++++++++++
 block/qcow2.c          |   7 +++
 5 files changed, 140 insertions(+), 2 deletions(-)

diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
index 5597e24474..795dbb21dd 100644
--- a/docs/interop/qcow2.txt
+++ b/docs/interop/qcow2.txt
@@ -208,6 +208,7 @@ version 2.
 
                     Available compression type values:
                         0: zlib <https://www.zlib.net/>
+                        1: zstd <http://github.com/facebook/zstd>
 
 
 === Header padding ===
diff --git a/configure b/configure
index caa65f5883..b2a0aa241a 100755
--- a/configure
+++ b/configure
@@ -1835,7 +1835,7 @@ disabled with --disable-FEATURE, default is enabled if 
available:
   lzfse           support of lzfse compression library
                   (for reading lzfse-compressed dmg images)
   zstd            support for zstd compression library
-                  (for migration compression)
+                  (for migration compression and qcow2 cluster compression)
   seccomp         seccomp support
   coroutine-pool  coroutine freelist (better performance)
   glusterfs       GlusterFS backend
diff --git a/qapi/block-core.json b/qapi/block-core.json
index a306484973..8953451818 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4401,11 +4401,12 @@
 # Compression type used in qcow2 image file
 #
 # @zlib: zlib compression, see <http://zlib.net/>
+# @zstd: zstd compression, see <http://github.com/facebook/zstd>
 #
 # Since: 5.0
 ##
 { 'enum': 'Qcow2CompressionType',
-  'data': [ 'zlib' ] }
+  'data': [ 'zlib', { 'name': 'zstd', 'if': 'defined(CONFIG_ZSTD)' } ] }
 
 ##
 # @BlockdevCreateOptionsQcow2:
diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
index 7dbaf53489..ee4bad8d5b 100644
--- a/block/qcow2-threads.c
+++ b/block/qcow2-threads.c
@@ -28,6 +28,11 @@
 #define ZLIB_CONST
 #include <zlib.h>
 
+#ifdef CONFIG_ZSTD
+#include <zstd.h>
+#include <zstd_errors.h>
+#endif
+
 #include "qcow2.h"
 #include "block/thread-pool.h"
 #include "crypto.h"
@@ -166,6 +171,120 @@ static ssize_t qcow2_zlib_decompress(void *dest, size_t 
dest_size,
     return ret;
 }
 
+#ifdef CONFIG_ZSTD
+
+/*
+ * qcow2_zstd_compress()
+ *
+ * Compress @src_size bytes of data using zstd compression method
+ *
+ * @dest - destination buffer, @dest_size bytes
+ * @src - source buffer, @src_size bytes
+ *
+ * Returns: compressed size on success
+ *          -ENOMEM destination buffer is not enough to store compressed data
+ *          -EIO    on any other error
+ */
+static ssize_t qcow2_zstd_compress(void *dest, size_t dest_size,
+                                   const void *src, size_t src_size)
+{
+    size_t ret;
+    ZSTD_outBuffer output = { dest, dest_size, 0 };
+    ZSTD_inBuffer input = { src, src_size, 0 };
+    ZSTD_CCtx *cctx = ZSTD_createCCtx();
+
+    if (!cctx) {
+        return -EIO;
+    }
+
+    ret = ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel,
+                                 ZSTD_CLEVEL_DEFAULT);
+    if (ZSTD_isError(ret)) {
+        ret = -EIO;
+        goto out;
+    }
+
+    {
+        /*
+         * Instruct zstd to compress the whole buffer and write
+         * the frame epilogue. This allows as to use zstd streaming
+         * semantics and don't store the compressed size for the
+         * zstd decompression.
+         */
+        ret = ZSTD_compressStream2(cctx, &output , &input, ZSTD_e_end);
+        if (ZSTD_isError(ret)) {
+            ret = -EIO;
+            goto out;
+        }
+        /* Dest buffer isn't big enough to store compressed content */
+        if (output.pos + ret > output.size) {
+            ret = -ENOMEM;
+            goto out;
+        }
+    } while (ret);
+
+    /* if no error, the input data must be fully consumed */
+    assert(input.pos == input.size);
+    /* make sure we can safely return compressed buffer size with ssize_t */
+    assert(output.pos <= SSIZE_MAX);
+    ret = output.pos;
+
+out:
+    ZSTD_freeCCtx(cctx);
+    return ret;
+}
+
+/*
+ * qcow2_zstd_decompress()
+ *
+ * Decompress some data (not more than @src_size bytes) to produce exactly
+ * @dest_size bytes using zstd compression method
+ *
+ * @dest - destination buffer, @dest_size bytes
+ * @src - source buffer, @src_size bytes
+ *
+ * Returns: 0 on success
+ *          -EIO on any error
+ */
+static ssize_t qcow2_zstd_decompress(void *dest, size_t dest_size,
+                                     const void *src, size_t src_size)
+{
+    size_t ret = 0;
+    ZSTD_outBuffer output = { dest, dest_size, 0 };
+    ZSTD_inBuffer input = { src, src_size, 0 };
+    ZSTD_DCtx *dctx = ZSTD_createDCtx();
+
+    if (!dctx) {
+        return -EIO;
+    }
+
+    {
+        ret = ZSTD_decompressStream(dctx, &output, &input);
+        if (ZSTD_isError(ret)) {
+            ret = -EIO;
+            goto out;
+        }
+        /*
+         * Dest buffer size is the image cluster size.
+         * It should be big enough to store uncompressed content.
+         * There shouldn't be any cases when the decompressed content
+         * size is greater then the cluster size.
+         */
+        assert(output.pos + ret <= output.size);
+    } while (ret);
+
+    /*
+     * If decompression went fine we must have the compressed
+     * cluser fully consumed and flushed
+     */
+    assert(output.pos == output.size);
+out:
+    ZSTD_freeDCtx(dctx);
+    return ret;
+
+}
+#endif
+
 static int qcow2_compress_pool_func(void *opaque)
 {
     Qcow2CompressData *data = opaque;
@@ -217,6 +336,11 @@ qcow2_co_compress(BlockDriverState *bs, void *dest, size_t 
dest_size,
         fn = qcow2_zlib_compress;
         break;
 
+#ifdef CONFIG_ZSTD
+    case QCOW2_COMPRESSION_TYPE_ZSTD:
+        fn = qcow2_zstd_compress;
+        break;
+#endif
     default:
         abort();
     }
@@ -249,6 +373,11 @@ qcow2_co_decompress(BlockDriverState *bs, void *dest, 
size_t dest_size,
         fn = qcow2_zlib_decompress;
         break;
 
+#ifdef CONFIG_ZSTD
+    case QCOW2_COMPRESSION_TYPE_ZSTD:
+        fn = qcow2_zstd_decompress;
+        break;
+#endif
     default:
         abort();
     }
diff --git a/block/qcow2.c b/block/qcow2.c
index 899b5541f5..6420d27a6d 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1246,6 +1246,9 @@ static int validate_compression_type(BDRVQcow2State *s, 
Error **errp)
 {
     switch (s->compression_type) {
     case QCOW2_COMPRESSION_TYPE_ZLIB:
+#ifdef CONFIG_ZSTD
+    case QCOW2_COMPRESSION_TYPE_ZSTD:
+#endif
         break;
 
     default:
@@ -3454,6 +3457,10 @@ qcow2_co_create(BlockdevCreateOptions *create_options, 
Error **errp)
         }
 
         switch (qcow2_opts->compression_type) {
+#ifdef CONFIG_ZSTD
+        case QCOW2_COMPRESSION_TYPE_ZSTD:
+            break;
+#endif
         default:
             error_setg(errp, "Unknown compression type");
             goto out;
-- 
2.17.0