fs/zfs/zio_compress.c

	zio_compress.c revision fa9e4066f08beec538e775443c5be79dd423fcab
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/zfs_context.h>
#include <sys/compress.h>
#include <sys/spa.h>
#include <sys/zio.h>
#include <sys/zio_compress.h>

/*
 * Compression vectors.
 */

zio_compress_info_t zio_compress_table[ZIO_COMPRESS_FUNCTIONS] = {
    NULL,           NULL,           "inherit",
    NULL,           NULL,           "on",
    NULL,           NULL,           "uncompressed",
    lzjb_compress,      lzjb_decompress,    "lzjb",
};

uint8_t
zio_compress_select(uint8_t child, uint8_t parent)
{
    ASSERT(child < ZIO_COMPRESS_FUNCTIONS);
    ASSERT(parent < ZIO_COMPRESS_FUNCTIONS);
    ASSERT(parent != ZIO_COMPRESS_INHERIT && parent != ZIO_COMPRESS_ON);

    if (child == ZIO_COMPRESS_INHERIT)
        return (parent);

    if (child == ZIO_COMPRESS_ON)
        return (ZIO_COMPRESS_ON_VALUE);

    return (child);
}

int
zio_compress_data(int cpfunc, void *src, uint64_t srcsize, void **destp,
    uint64_t *destsizep, uint64_t *destbufsizep)
{
    uint64_t *word, *word_end;
    uint64_t ciosize, gapsize, destbufsize;
    zio_compress_info_t *ci = &zio_compress_table[cpfunc];
    char *dest;
    uint_t allzero;

    ASSERT((uint_t)cpfunc < ZIO_COMPRESS_FUNCTIONS);
    ASSERT(ci->ci_compress != NULL);

    /*
     * If the data is all zeroes, we don't even need to allocate
     * a block for it.  We indicate this by setting *destsizep = 0.
     */
    allzero = 1;
    word = src;
    word_end = (uint64_t *)(uintptr_t)((uintptr_t)word + srcsize);
    while (word < word_end) {
        if (*word++ != 0) {
            allzero = 0;
            break;
        }
    }
    if (allzero) {
        *destp = NULL;
        *destsizep = 0;
        *destbufsizep = 0;
        return (1);
    }

    /* Compress at least 12.5% */
    destbufsize = P2ALIGN(srcsize - (srcsize >> 3), SPA_MINBLOCKSIZE);
    if (destbufsize == 0)
        return (0);
    dest = zio_buf_alloc(destbufsize);

    ciosize = ci->ci_compress(src, dest, (size_t)srcsize,
        (size_t)destbufsize);
    if (ciosize > destbufsize) {
        zio_buf_free(dest, destbufsize);
        return (0);
    }

    /* Cool.  We compressed at least as much as we were hoping to. */

    /* For security, make sure we don't write random heap crap to disk */
    gapsize = P2ROUNDUP(ciosize, SPA_MINBLOCKSIZE) - ciosize;
    if (gapsize != 0) {
        bzero(dest + ciosize, gapsize);
        ciosize += gapsize;
    }

    ASSERT3U(ciosize, <=, destbufsize);
    ASSERT(P2PHASE(ciosize, SPA_MINBLOCKSIZE) == 0);
    *destp = dest;
    *destsizep = ciosize;
    *destbufsizep = destbufsize;

    return (1);
}

int
zio_decompress_data(int cpfunc, void *src, uint64_t srcsize,
    void *dest, uint64_t destsize)
{
    ASSERT((uint_t)cpfunc < ZIO_COMPRESS_FUNCTIONS);

    return (zio_compress_table[cpfunc].ci_decompress(src, dest,
        srcsize, destsize));
}