xemu/block/blklogwrites.c

/*
 * Write logging blk driver based on blkverify and blkdebug.
 *
 * Copyright (c) 2017 Tuomas Tynkkynen <tuomas@tuxera.com>
 * Copyright (c) 2018 Aapo Vienamo <aapo@tuxera.com>
 * Copyright (c) 2018 Ari Sundholm <ari@tuxera.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/sockets.h" /* for EINPROGRESS on Windows */
#include "block/block_int.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qstring.h"
#include "qemu/cutils.h"
#include "qemu/option.h"

/* Disk format stuff - taken from Linux drivers/md/dm-log-writes.c */

#define LOG_FLUSH_FLAG   (1 << 0)
#define LOG_FUA_FLAG     (1 << 1)
#define LOG_DISCARD_FLAG (1 << 2)
#define LOG_MARK_FLAG    (1 << 3)

#define WRITE_LOG_VERSION 1ULL
#define WRITE_LOG_MAGIC 0x6a736677736872ULL

/* All fields are little-endian. */
struct log_write_super {
    uint64_t magic;
    uint64_t version;
    uint64_t nr_entries;
    uint32_t sectorsize;
} QEMU_PACKED;

struct log_write_entry {
    uint64_t sector;
    uint64_t nr_sectors;
    uint64_t flags;
    uint64_t data_len;
} QEMU_PACKED;

/* End of disk format structures. */

typedef struct {
    BdrvChild *log_file;
    uint32_t sectorsize;
    uint32_t sectorbits;
    uint64_t cur_log_sector;
    uint64_t nr_entries;
} BDRVBlkLogWritesState;

static QemuOptsList runtime_opts = {
    .name = "blklogwrites",
    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
    .desc = {
        {
            .name = "log-sector-size",
            .type = QEMU_OPT_SIZE,
            .help = "Log sector size",
        },
        { /* end of list */ }
    },
};

static inline uint32_t blk_log_writes_log2(uint32_t value)
{
    assert(value > 0);
    return 31 - clz32(value);
}

static int blk_log_writes_open(BlockDriverState *bs, QDict *options, int flags,
                               Error **errp)
{
    BDRVBlkLogWritesState *s = bs->opaque;
    QemuOpts *opts;
    Error *local_err = NULL;
    int ret;
    uint64_t log_sector_size;

    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
    qemu_opts_absorb_qdict(opts, options, &local_err);
    if (local_err) {
        ret = -EINVAL;
        error_propagate(errp, local_err);
        goto fail;
    }

    /* Open the file */
    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file, false,
                               &local_err);
    if (local_err) {
        ret = -EINVAL;
        error_propagate(errp, local_err);
        goto fail;
    }

    log_sector_size = qemu_opt_get_size(opts, "log-sector-size",
                                        BDRV_SECTOR_SIZE);

    if (log_sector_size > (1ull << 23) || !is_power_of_2(log_sector_size)) {
        ret = -EINVAL;
        error_setg(errp, "Invalid log sector size %"PRIu64, log_sector_size);
        goto fail;
    }

    s->sectorsize = log_sector_size;
    s->sectorbits = blk_log_writes_log2(log_sector_size);
    s->cur_log_sector = 1;
    s->nr_entries = 0;

    /* Open the log file */
    s->log_file = bdrv_open_child(NULL, options, "log", bs, &child_file, false,
                                  &local_err);
    if (local_err) {
        ret = -EINVAL;
        error_propagate(errp, local_err);
        goto fail;
    }

    ret = 0;
fail:
    if (ret < 0) {
        bdrv_unref_child(bs, bs->file);
        bs->file = NULL;
    }
    qemu_opts_del(opts);
    return ret;
}

static void blk_log_writes_close(BlockDriverState *bs)
{
    BDRVBlkLogWritesState *s = bs->opaque;

    bdrv_unref_child(bs, s->log_file);
    s->log_file = NULL;
}

static int64_t blk_log_writes_getlength(BlockDriverState *bs)
{
    return bdrv_getlength(bs->file->bs);
}

static void blk_log_writes_refresh_filename(BlockDriverState *bs,
                                            QDict *options)
{
    BDRVBlkLogWritesState *s = bs->opaque;

    /* bs->file->bs has already been refreshed */
    bdrv_refresh_filename(s->log_file->bs);

    if (bs->file->bs->full_open_options
        && s->log_file->bs->full_open_options)
    {
        QDict *opts = qdict_new();
        qdict_put_str(opts, "driver", "blklogwrites");

        qobject_ref(bs->file->bs->full_open_options);
        qdict_put_obj(opts, "file", QOBJECT(bs->file->bs->full_open_options));
        qobject_ref(s->log_file->bs->full_open_options);
        qdict_put_obj(opts, "log",
                      QOBJECT(s->log_file->bs->full_open_options));
        qdict_put_int(opts, "log-sector-size", s->sectorsize);

        bs->full_open_options = opts;
    }
}

static void blk_log_writes_child_perm(BlockDriverState *bs, BdrvChild *c,
                                      const BdrvChildRole *role,
                                      BlockReopenQueue *ro_q,
                                      uint64_t perm, uint64_t shrd,
                                      uint64_t *nperm, uint64_t *nshrd)
{
    if (!c) {
        *nperm = perm & DEFAULT_PERM_PASSTHROUGH;
        *nshrd = (shrd & DEFAULT_PERM_PASSTHROUGH) | DEFAULT_PERM_UNCHANGED;
        return;
    }

    if (!strcmp(c->name, "log")) {
        bdrv_format_default_perms(bs, c, role, ro_q, perm, shrd, nperm, nshrd);
    } else {
        bdrv_filter_default_perms(bs, c, role, ro_q, perm, shrd, nperm, nshrd);
    }
}

static void blk_log_writes_refresh_limits(BlockDriverState *bs, Error **errp)
{
    BDRVBlkLogWritesState *s = bs->opaque;
    bs->bl.request_alignment = s->sectorsize;
}

static int coroutine_fn
blk_log_writes_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
                         QEMUIOVector *qiov, int flags)
{
    return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
}

typedef struct BlkLogWritesFileReq {
    BlockDriverState *bs;
    uint64_t offset;
    uint64_t bytes;
    int file_flags;
    QEMUIOVector *qiov;
    int (*func)(struct BlkLogWritesFileReq *r);
    int file_ret;
} BlkLogWritesFileReq;

typedef struct {
    BlockDriverState *bs;
    QEMUIOVector *qiov;
    struct log_write_entry entry;
    uint64_t zero_size;
    int log_ret;
} BlkLogWritesLogReq;

static void coroutine_fn blk_log_writes_co_do_log(BlkLogWritesLogReq *lr)
{
    BDRVBlkLogWritesState *s = lr->bs->opaque;
    uint64_t cur_log_offset = s->cur_log_sector << s->sectorbits;

    s->nr_entries++;
    s->cur_log_sector +=
            ROUND_UP(lr->qiov->size, s->sectorsize) >> s->sectorbits;

    lr->log_ret = bdrv_co_pwritev(s->log_file, cur_log_offset, lr->qiov->size,
                                  lr->qiov, 0);

    /* Logging for the "write zeroes" operation */
    if (lr->log_ret == 0 && lr->zero_size) {
        cur_log_offset = s->cur_log_sector << s->sectorbits;
        s->cur_log_sector +=
                ROUND_UP(lr->zero_size, s->sectorsize) >> s->sectorbits;

        lr->log_ret = bdrv_co_pwrite_zeroes(s->log_file, cur_log_offset,
                                            lr->zero_size, 0);
    }

    /* Update super block on flush */
    if (lr->log_ret == 0 && lr->entry.flags & LOG_FLUSH_FLAG) {
        struct log_write_super super = {
            .magic      = cpu_to_le64(WRITE_LOG_MAGIC),
            .version    = cpu_to_le64(WRITE_LOG_VERSION),
            .nr_entries = cpu_to_le64(s->nr_entries),
            .sectorsize = cpu_to_le32(s->sectorsize),
        };
        void *zeroes = g_malloc0(s->sectorsize - sizeof(super));
        QEMUIOVector qiov;

        qemu_iovec_init(&qiov, 2);
        qemu_iovec_add(&qiov, &super, sizeof(super));
        qemu_iovec_add(&qiov, zeroes, s->sectorsize - sizeof(super));

        lr->log_ret =
            bdrv_co_pwritev(s->log_file, 0, s->sectorsize, &qiov, 0);
        if (lr->log_ret == 0) {
            lr->log_ret = bdrv_co_flush(s->log_file->bs);
        }
        qemu_iovec_destroy(&qiov);
        g_free(zeroes);
    }
}

static void coroutine_fn blk_log_writes_co_do_file(BlkLogWritesFileReq *fr)
{
    fr->file_ret = fr->func(fr);
}

static int coroutine_fn
blk_log_writes_co_log(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
                      QEMUIOVector *qiov, int flags,
                      int (*file_func)(BlkLogWritesFileReq *r),
                      uint64_t entry_flags, bool is_zero_write)
{
    QEMUIOVector log_qiov;
    size_t niov = qiov ? qiov->niov : 0;
    BDRVBlkLogWritesState *s = bs->opaque;
    BlkLogWritesFileReq fr = {
        .bs         = bs,
        .offset     = offset,
        .bytes      = bytes,
        .file_flags = flags,
        .qiov       = qiov,
        .func       = file_func,
    };
    BlkLogWritesLogReq lr = {
        .bs             = bs,
        .qiov           = &log_qiov,
        .entry = {
            .sector     = cpu_to_le64(offset >> s->sectorbits),
            .nr_sectors = cpu_to_le64(bytes >> s->sectorbits),
            .flags      = cpu_to_le64(entry_flags),
            .data_len   = 0,
        },
        .zero_size = is_zero_write ? bytes : 0,
    };
    void *zeroes = g_malloc0(s->sectorsize - sizeof(lr.entry));

    assert((1 << s->sectorbits) == s->sectorsize);
    assert(bs->bl.request_alignment == s->sectorsize);
    assert(QEMU_IS_ALIGNED(offset, bs->bl.request_alignment));
    assert(QEMU_IS_ALIGNED(bytes, bs->bl.request_alignment));

    qemu_iovec_init(&log_qiov, niov + 2);
    qemu_iovec_add(&log_qiov, &lr.entry, sizeof(lr.entry));
    qemu_iovec_add(&log_qiov, zeroes, s->sectorsize - sizeof(lr.entry));
    if (qiov) {
        qemu_iovec_concat(&log_qiov, qiov, 0, qiov->size);
    }

    blk_log_writes_co_do_file(&fr);
    blk_log_writes_co_do_log(&lr);

    qemu_iovec_destroy(&log_qiov);
    g_free(zeroes);

    if (lr.log_ret < 0) {
        return lr.log_ret;
    }

    return fr.file_ret;
}

static int coroutine_fn
blk_log_writes_co_do_file_pwritev(BlkLogWritesFileReq *fr)
{
    return bdrv_co_pwritev(fr->bs->file, fr->offset, fr->bytes,
                           fr->qiov, fr->file_flags);
}

static int coroutine_fn
blk_log_writes_co_do_file_pwrite_zeroes(BlkLogWritesFileReq *fr)
{
    return bdrv_co_pwrite_zeroes(fr->bs->file, fr->offset, fr->bytes,
                                 fr->file_flags);
}

static int coroutine_fn blk_log_writes_co_do_file_flush(BlkLogWritesFileReq *fr)
{
    return bdrv_co_flush(fr->bs->file->bs);
}

static int coroutine_fn
blk_log_writes_co_do_file_pdiscard(BlkLogWritesFileReq *fr)
{
    return bdrv_co_pdiscard(fr->bs->file->bs, fr->offset, fr->bytes);
}

static int coroutine_fn
blk_log_writes_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
                          QEMUIOVector *qiov, int flags)
{
    return blk_log_writes_co_log(bs, offset, bytes, qiov, flags,
                                 blk_log_writes_co_do_file_pwritev, 0, false);
}

static int coroutine_fn
blk_log_writes_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
                                BdrvRequestFlags flags)
{
    return blk_log_writes_co_log(bs, offset, bytes, NULL, flags,
                                 blk_log_writes_co_do_file_pwrite_zeroes, 0,
                                 true);
}

static int coroutine_fn blk_log_writes_co_flush_to_disk(BlockDriverState *bs)
{
    return blk_log_writes_co_log(bs, 0, 0, NULL, 0,
                                 blk_log_writes_co_do_file_flush,
                                 LOG_FLUSH_FLAG, false);
}

static int coroutine_fn
blk_log_writes_co_pdiscard(BlockDriverState *bs, int64_t offset, int count)
{
    return blk_log_writes_co_log(bs, offset, count, NULL, 0,
                                 blk_log_writes_co_do_file_pdiscard,
                                 LOG_DISCARD_FLAG, false);
}

static BlockDriver bdrv_blk_log_writes = {
    .format_name            = "blklogwrites",
    .instance_size          = sizeof(BDRVBlkLogWritesState),

    .bdrv_open              = blk_log_writes_open,
    .bdrv_close             = blk_log_writes_close,
    .bdrv_getlength         = blk_log_writes_getlength,
    .bdrv_refresh_filename  = blk_log_writes_refresh_filename,
    .bdrv_child_perm        = blk_log_writes_child_perm,
    .bdrv_refresh_limits    = blk_log_writes_refresh_limits,

    .bdrv_co_preadv         = blk_log_writes_co_preadv,
    .bdrv_co_pwritev        = blk_log_writes_co_pwritev,
    .bdrv_co_pwrite_zeroes  = blk_log_writes_co_pwrite_zeroes,
    .bdrv_co_flush_to_disk  = blk_log_writes_co_flush_to_disk,
    .bdrv_co_pdiscard       = blk_log_writes_co_pdiscard,
    .bdrv_co_block_status   = bdrv_co_block_status_from_file,

    .is_filter              = true,
};

static void bdrv_blk_log_writes_init(void)
{
    bdrv_register(&bdrv_blk_log_writes);
}

block_init(bdrv_blk_log_writes_init);