fs/zfs/zio_checksum.c

	zio_checksum.c revision 6b4acc8bd9d480535a4d057e291dc7c049f664d9
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2006 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/spa.h>
#include <sys/zio.h>
#include <sys/zio_checksum.h>

/*
 * Checksum vectors.
 *
 * In the SPA, everything is checksummed.  We support checksum vectors
 * for three distinct reasons:
 *
 *   1. Different kinds of data need different levels of protection.
 *  For SPA metadata, we always want a very strong checksum.
 *  For user data, we let users make the trade-off between speed
 *  and checksum strength.
 *
 *   2. Cryptographic hash and MAC algorithms are an area of active research.
 *  It is likely that in future hash functions will be at least as strong
 *  as current best-of-breed, and may be substantially faster as well.
 *  We want the ability to take advantage of these new hashes as soon as
 *  they become available.
 *
 *   3. If someone develops hardware that can compute a strong hash quickly,
 *  we want the ability to take advantage of that hardware.
 *
 * Of course, we don't want a checksum upgrade to invalidate existing
 * data, so we store the checksum *function* in five bits of the DVA.
 * This gives us room for up to 32 different checksum functions.
 *
 * When writing a block, we always checksum it with the latest-and-greatest
 * checksum function of the appropriate strength.  When reading a block,
 * we compare the expected checksum against the actual checksum, which we
 * compute via the checksum function specified in the DVA encoding.
 */

/*ARGSUSED*/
static void
zio_checksum_off(const void *buf, uint64_t size, zio_cksum_t *zcp)
{
    ZIO_SET_CHECKSUM(zcp, 0, 0, 0, 0);
}

zio_checksum_info_t zio_checksum_table[ZIO_CHECKSUM_FUNCTIONS] = {
    {{NULL,         NULL},          0, 0,   "inherit"},
    {{NULL,         NULL},          0, 0,   "on"},
    {{zio_checksum_off, zio_checksum_off},  0, 0,   "off"},
    {{zio_checksum_SHA256,  zio_checksum_SHA256},   1, 1,   "label"},
    {{zio_checksum_SHA256,  zio_checksum_SHA256},   1, 1,   "gang_header"},
    {{fletcher_2_native,    fletcher_2_byteswap},   0, 1,   "zilog"},
    {{fletcher_2_native,    fletcher_2_byteswap},   0, 0,   "fletcher2"},
    {{fletcher_4_native,    fletcher_4_byteswap},   1, 0,   "fletcher4"},
    {{zio_checksum_SHA256,  zio_checksum_SHA256},   1, 0,   "SHA256"},
};

uint8_t
zio_checksum_select(uint8_t child, uint8_t parent)
{
    ASSERT(child < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(parent < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(parent != ZIO_CHECKSUM_INHERIT && parent != ZIO_CHECKSUM_ON);

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

    if (child == ZIO_CHECKSUM_ON)
        return (ZIO_CHECKSUM_ON_VALUE);

    return (child);
}

/*
 * Generate the checksum.
 */
void
zio_checksum(uint_t checksum, zio_cksum_t *zcp, void *data, uint64_t size)
{
    zio_block_tail_t *zbt = (zio_block_tail_t *)((char *)data + size) - 1;
    zio_checksum_info_t *ci = &zio_checksum_table[checksum];
    zio_cksum_t zbt_cksum;

    ASSERT(checksum < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(ci->ci_func[0] != NULL);

    if (ci->ci_zbt) {
        *zcp = zbt->zbt_cksum;
        zbt->zbt_magic = ZBT_MAGIC;
        ci->ci_func[0](data, size, &zbt_cksum);
        zbt->zbt_cksum = zbt_cksum;
    } else {
        ci->ci_func[0](data, size, zcp);
    }
}

int
zio_checksum_error(zio_t *zio)
{
    blkptr_t *bp = zio->io_bp;
    zio_cksum_t zc = bp->blk_cksum;
    uint_t checksum = BP_IS_GANG(bp) ? ZIO_CHECKSUM_GANG_HEADER :
        BP_GET_CHECKSUM(bp);
    int byteswap = BP_SHOULD_BYTESWAP(bp);
    void *data = zio->io_data;
    uint64_t size = ZIO_GET_IOSIZE(zio);
    zio_block_tail_t *zbt = (zio_block_tail_t *)((char *)data + size) - 1;
    zio_checksum_info_t *ci = &zio_checksum_table[checksum];
    zio_cksum_t actual_cksum, expected_cksum;

    if (checksum >= ZIO_CHECKSUM_FUNCTIONS || ci->ci_func[0] == NULL)
        return (EINVAL);

    if (ci->ci_zbt) {
        if (checksum == ZIO_CHECKSUM_GANG_HEADER)
            zio_set_gang_verifier(zio, &zc);

        if (zbt->zbt_magic == BSWAP_64(ZBT_MAGIC)) {
            expected_cksum = zbt->zbt_cksum;
            byteswap_uint64_array(&expected_cksum,
                sizeof (zio_cksum_t));
            zbt->zbt_cksum = zc;
            byteswap_uint64_array(&zbt->zbt_cksum,
                sizeof (zio_cksum_t));
            ci->ci_func[1](data, size, &actual_cksum);
            zbt->zbt_cksum = expected_cksum;
            byteswap_uint64_array(&zbt->zbt_cksum,
                sizeof (zio_cksum_t));
        } else {
            expected_cksum = zbt->zbt_cksum;
            zbt->zbt_cksum = zc;
            ci->ci_func[0](data, size, &actual_cksum);
            zbt->zbt_cksum = expected_cksum;
        }
        zc = expected_cksum;
    } else {
        ASSERT(!BP_IS_GANG(bp));
        ci->ci_func[byteswap](data, size, &actual_cksum);
    }

    if (!ZIO_CHECKSUM_EQUAL(actual_cksum, zc))
        return (ECKSUM);

    if (zio_injection_enabled && !zio->io_error)
        return (zio_handle_fault_injection(zio, ECKSUM));

    return (0);
}