Commit 2714f13d authored by Vladimir Sementsov-Ogievskiy's avatar Vladimir Sementsov-Ogievskiy Committed by Kevin Wolf
Browse files

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: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 88481329

block/qcow2.c

+51 −27
Original line number Diff line number Diff line
@@ -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) {