sbin/hammer: Add is_regfile() (avoid directly using a string literal)

[dragonfly.git] / sbin / hammer / ondisk.c

/*
 * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/diskslice.h>
#include <sys/diskmbr.h>

#include "hammer_util.h"

static void check_volume(struct volume_info *volume);
static void get_buffer_readahead(struct buffer_info *base);
static __inline int readhammervol(struct volume_info *volume);
static __inline int readhammerbuf(struct buffer_info *buffer);
static __inline int writehammervol(struct volume_info *volume);
static __inline int writehammerbuf(struct buffer_info *buffer);

uuid_t Hammer_FSType;
uuid_t Hammer_FSId;
int UseReadBehind = -4;
int UseReadAhead = 4;
int DebugOpt;
uint32_t HammerVersion = -1;

TAILQ_HEAD(volume_list, volume_info);
static struct volume_list VolList = TAILQ_HEAD_INITIALIZER(VolList);
static int valid_hammer_volumes;

static __inline
int
buffer_hash(hammer_off_t zone2_offset)
{
        int hi;

        hi = (int)(zone2_offset / HAMMER_BUFSIZE) & HAMMER_BUFLISTMASK;
        return(hi);
}

static struct buffer_info*
find_buffer(hammer_off_t zone2_offset)
{
        struct volume_info *volume;
        struct buffer_info *buffer;
        int hi;

        volume = get_volume(HAMMER_VOL_DECODE(zone2_offset));
        assert(volume);

        hi = buffer_hash(zone2_offset);
        TAILQ_FOREACH(buffer, &volume->buffer_lists[hi], entry)
                if (buffer->zone2_offset == zone2_offset)
                        return(buffer);
        return(NULL);
}

static
struct volume_info *
__alloc_volume(const char *volname, int oflags)
{
        struct volume_info *volume;
        int i;

        volume = calloc(1, sizeof(*volume));
        volume->vol_no = -1;
        volume->rdonly = (oflags == O_RDONLY);
        volume->name = strdup(volname);
        volume->fd = open(volume->name, oflags);
        if (volume->fd < 0)
                err(1, "alloc_volume: Failed to open %s", volume->name);
        check_volume(volume);

        volume->ondisk = calloc(1, HAMMER_BUFSIZE);

        for (i = 0; i < HAMMER_BUFLISTS; ++i)
                TAILQ_INIT(&volume->buffer_lists[i]);

        return(volume);
}

static void
__add_volume(struct volume_info *volume)
{
        struct volume_info *scan;
        struct stat st1, st2;

        if (fstat(volume->fd, &st1) != 0)
                errx(1, "add_volume: %s: Failed to stat", volume->name);

        TAILQ_FOREACH(scan, &VolList, entry) {
                if (scan->vol_no == volume->vol_no) {
                        errx(1, "add_volume: %s: Duplicate volume number %d "
                                "against %s",
                                volume->name, volume->vol_no, scan->name);
                }
                if (fstat(scan->fd, &st2) != 0) {
                        errx(1, "add_volume: %s: Failed to stat %s",
                                volume->name, scan->name);
                }
                if ((st1.st_ino == st2.st_ino) && (st1.st_dev == st2.st_dev)) {
                        errx(1, "add_volume: %s: Specified more than once",
                                volume->name);
                }
        }

        TAILQ_INSERT_TAIL(&VolList, volume, entry);
}

static void
__verify_volume(struct volume_info *volume)
{
        hammer_volume_ondisk_t ondisk = volume->ondisk;

        if (ondisk->vol_signature != HAMMER_FSBUF_VOLUME) {
                errx(1, "verify_volume: Invalid volume signature %016jx",
                        ondisk->vol_signature);
        }
        if (ondisk->vol_rootvol != HAMMER_ROOT_VOLNO) {
                errx(1, "verify_volume: Invalid root volume# %d",
                        ondisk->vol_rootvol);
        }
        if (bcmp(&Hammer_FSType, &ondisk->vol_fstype, sizeof(Hammer_FSType))) {
                errx(1, "verify_volume: %s: Header does not indicate "
                        "that this is a HAMMER volume", volume->name);
        }
        if (bcmp(&Hammer_FSId, &ondisk->vol_fsid, sizeof(Hammer_FSId))) {
                errx(1, "verify_volume: %s: FSId does not match other volumes!",
                        volume->name);
        }
}

/*
 * Initialize a volume structure and ondisk vol_no field.
 */
struct volume_info *
init_volume(const char *filename, int oflags, int32_t vol_no)
{
        struct volume_info *volume;

        volume = __alloc_volume(filename, oflags);
        volume->vol_no = volume->ondisk->vol_no = vol_no;

        __add_volume(volume);

        return(volume);
}

/*
 * Initialize a volume structure and read ondisk volume header.
 */
struct volume_info*
load_volume(const char *filename, int oflags, int verify)
{
        struct volume_info *volume;
        int n;

        volume = __alloc_volume(filename, oflags);

        n = readhammervol(volume);
        if (n == -1) {
                err(1, "load_volume: %s: Read failed at offset 0",
                    volume->name);
        }
        volume->vol_no = volume->ondisk->vol_no;
        HammerVersion = volume->ondisk->vol_version;

        if (valid_hammer_volumes++ == 0)
                Hammer_FSId = volume->ondisk->vol_fsid;
        if (verify)
                __verify_volume(volume);

        __add_volume(volume);

        return(volume);
}

/*
 * Check basic volume characteristics.
 */
static void
check_volume(struct volume_info *volume)
{
        struct partinfo pinfo;
        struct stat st;

        /*
         * Get basic information about the volume
         */
        if (ioctl(volume->fd, DIOCGPART, &pinfo) < 0) {
                /*
                 * Allow the formatting of regular files as HAMMER volumes
                 */
                if (fstat(volume->fd, &st) < 0)
                        err(1, "Unable to stat %s", volume->name);
                volume->size = st.st_size;
                volume->type = "REGFILE";
        } else {
                /*
                 * When formatting a block device as a HAMMER volume the
                 * sector size must be compatible.  HAMMER uses 16384 byte
                 * filesystem buffers.
                 */
                if (pinfo.reserved_blocks) {
                        errx(1, "HAMMER cannot be placed in a partition "
                                "which overlaps the disklabel or MBR");
                }
                if (pinfo.media_blksize > HAMMER_BUFSIZE ||
                    HAMMER_BUFSIZE % pinfo.media_blksize) {
                        errx(1, "A media sector size of %d is not supported",
                             pinfo.media_blksize);
                }

                volume->size = pinfo.media_size;
                volume->device_offset = pinfo.media_offset;
                volume->type = "DEVICE";
        }
}

int
is_regfile(struct volume_info *volume)
{
        return(strcmp(volume->type, "REGFILE") ? 0 : 1);
}

void
assert_volume_offset(struct volume_info *volume)
{
        assert(hammer_is_zone_raw_buffer(volume->vol_free_off));
        assert(hammer_is_zone_raw_buffer(volume->vol_free_end));
        if (volume->vol_free_off >= volume->vol_free_end)
                errx(1, "Ran out of room, filesystem too small");
}

struct volume_info *
get_volume(int32_t vol_no)
{
        struct volume_info *volume;

        TAILQ_FOREACH(volume, &VolList, entry) {
                if (volume->vol_no == vol_no)
                        break;
        }

        return(volume);
}

struct volume_info *
get_root_volume(void)
{
        return(get_volume(HAMMER_ROOT_VOLNO));
}

static hammer_off_t
__blockmap_xlate_to_zone2(hammer_off_t buf_offset)
{
        hammer_off_t zone2_offset;
        int error = 0;

        if (hammer_is_zone_raw_buffer(buf_offset))
                zone2_offset = buf_offset;
        else
                zone2_offset = blockmap_lookup(buf_offset, &error);

        if (error)
                return(HAMMER_OFF_BAD);
        assert(hammer_is_zone_raw_buffer(zone2_offset));

        return(zone2_offset);
}

static struct buffer_info *
__alloc_buffer(hammer_off_t zone2_offset, int isnew)
{
        struct volume_info *volume;
        struct buffer_info *buffer;
        int hi;

        volume = get_volume(HAMMER_VOL_DECODE(zone2_offset));
        assert(volume != NULL);

        buffer = calloc(1, sizeof(*buffer));
        buffer->zone2_offset = zone2_offset;
        buffer->raw_offset = hammer_xlate_to_phys(volume->ondisk, zone2_offset);
        buffer->volume = volume;
        buffer->ondisk = calloc(1, HAMMER_BUFSIZE);

        if (isnew <= 0) {
                if (readhammerbuf(buffer) == -1) {
                        err(1, "Failed to read %s:%016jx at %016jx",
                            volume->name,
                            (intmax_t)buffer->zone2_offset,
                            (intmax_t)buffer->raw_offset);
                }
        }

        hi = buffer_hash(zone2_offset);
        TAILQ_INSERT_TAIL(&volume->buffer_lists[hi], buffer, entry);
        hammer_cache_add(&buffer->cache);

        return(buffer);
}

/*
 * Acquire the 16KB buffer for specified zone offset.
 */
static struct buffer_info *
get_buffer(hammer_off_t buf_offset, int isnew)
{
        struct buffer_info *buffer;
        hammer_off_t zone2_offset;
        int dora = 0;

        zone2_offset = __blockmap_xlate_to_zone2(buf_offset);
        if (zone2_offset == HAMMER_OFF_BAD)
                return(NULL);

        zone2_offset &= ~HAMMER_BUFMASK64;
        buffer = find_buffer(zone2_offset);

        if (buffer == NULL) {
                buffer = __alloc_buffer(zone2_offset, isnew);
                dora = (isnew == 0);
        } else {
                assert(isnew != -1);
                hammer_cache_used(&buffer->cache);
        }
        assert(buffer->ondisk != NULL);

        ++buffer->cache.refs;
        hammer_cache_flush();

        if (isnew > 0) {
                assert(buffer->cache.modified == 0);
                bzero(buffer->ondisk, HAMMER_BUFSIZE);
                buffer->cache.modified = 1;
        }
        if (dora)
                get_buffer_readahead(buffer);
        return(buffer);
}

static void
get_buffer_readahead(struct buffer_info *base)
{
        struct buffer_info *buffer;
        struct volume_info *volume;
        hammer_off_t zone2_offset;
        int64_t raw_offset;
        int ri = UseReadBehind;
        int re = UseReadAhead;

        raw_offset = base->raw_offset + ri * HAMMER_BUFSIZE;
        volume = base->volume;

        while (ri < re) {
                if (raw_offset >= volume->ondisk->vol_buf_end)
                        break;
                if (raw_offset < volume->ondisk->vol_buf_beg || ri == 0) {
                        ++ri;
                        raw_offset += HAMMER_BUFSIZE;
                        continue;
                }
                zone2_offset = HAMMER_ENCODE_RAW_BUFFER(volume->vol_no,
                        raw_offset - volume->ondisk->vol_buf_beg);
                buffer = find_buffer(zone2_offset);
                if (buffer == NULL) {
                        /* call with -1 to prevent another readahead */
                        buffer = get_buffer(zone2_offset, -1);
                        rel_buffer(buffer);
                }
                ++ri;
                raw_offset += HAMMER_BUFSIZE;
        }
}

void
rel_buffer(struct buffer_info *buffer)
{
        struct volume_info *volume;
        int hi;

        if (buffer == NULL)
                return;
        assert(buffer->cache.refs > 0);
        if (--buffer->cache.refs == 0) {
                if (buffer->cache.delete) {
                        hi = buffer_hash(buffer->zone2_offset);
                        volume = buffer->volume;
                        if (buffer->cache.modified)
                                flush_buffer(buffer);
                        TAILQ_REMOVE(&volume->buffer_lists[hi], buffer, entry);
                        hammer_cache_del(&buffer->cache);
                        free(buffer->ondisk);
                        free(buffer);
                }
        }
}

/*
 * Retrieve a pointer to a buffer data given a buffer offset.  The underlying
 * bufferp is freed if isnew or the offset is out of range of the cached data.
 * If bufferp is freed a referenced buffer is loaded into it.
 */
void *
get_buffer_data(hammer_off_t buf_offset, struct buffer_info **bufferp,
                int isnew)
{
        hammer_off_t xor;

        if (*bufferp != NULL) {
                /* XXX xor is always non zero for indirect zones */
                xor = HAMMER_OFF_LONG_ENCODE(buf_offset) ^
                      HAMMER_OFF_LONG_ENCODE((*bufferp)->zone2_offset);
                if (isnew > 0 || (xor & ~HAMMER_BUFMASK64)) {
                        rel_buffer(*bufferp);
                        *bufferp = NULL;
                }
        }

        if (*bufferp == NULL) {
                *bufferp = get_buffer(buf_offset, isnew);
                if (*bufferp == NULL)
                        return(NULL);
        }

        return(((char *)(*bufferp)->ondisk) +
                ((int32_t)buf_offset & HAMMER_BUFMASK));
}

/*
 * Allocate HAMMER elements - B-Tree nodes
 */
hammer_node_ondisk_t
alloc_btree_node(hammer_off_t *offp, struct buffer_info **data_bufferp)
{
        hammer_node_ondisk_t node;

        node = alloc_blockmap(HAMMER_ZONE_BTREE_INDEX, sizeof(*node),
                              offp, data_bufferp);
        bzero(node, sizeof(*node));
        return(node);
}

/*
 * Allocate HAMMER elements - meta data (inode, direntry, PFS, etc)
 */
void *
alloc_meta_element(hammer_off_t *offp, int32_t data_len,
                   struct buffer_info **data_bufferp)
{
        void *data;

        data = alloc_blockmap(HAMMER_ZONE_META_INDEX, data_len,
                              offp, data_bufferp);
        bzero(data, data_len);
        return(data);
}

/*
 * Format a new blockmap.  This is mostly a degenerate case because
 * all allocations are now actually done from the freemap.
 */
void
format_blockmap(struct volume_info *root_vol, int zone, hammer_off_t offset)
{
        hammer_blockmap_t blockmap;
        hammer_off_t zone_base;

        /* Only root volume needs formatting */
        assert(root_vol->vol_no == HAMMER_ROOT_VOLNO);

        assert(hammer_is_index_record(zone));

        blockmap = &root_vol->ondisk->vol0_blockmap[zone];
        zone_base = HAMMER_ZONE_ENCODE(zone, offset);

        bzero(blockmap, sizeof(*blockmap));
        blockmap->phys_offset = 0;
        blockmap->first_offset = zone_base;
        blockmap->next_offset = zone_base;
        blockmap->alloc_offset = HAMMER_ENCODE(zone, 255, -1);
        hammer_crc_set_blockmap(HammerVersion, blockmap);
}

/*
 * Format a new freemap.  Set all layer1 entries to UNAVAIL.  The initialize
 * code will load each volume's freemap.
 */
void
format_freemap(struct volume_info *root_vol)
{
        struct buffer_info *buffer = NULL;
        hammer_off_t layer1_offset;
        hammer_blockmap_t blockmap;
        hammer_blockmap_layer1_t layer1;
        int i, isnew;

        /* Only root volume needs formatting */
        assert(root_vol->vol_no == HAMMER_ROOT_VOLNO);

        layer1_offset = bootstrap_bigblock(root_vol);
        for (i = 0; i < HAMMER_BIGBLOCK_SIZE; i += sizeof(*layer1)) {
                isnew = ((i % HAMMER_BUFSIZE) == 0);
                layer1 = get_buffer_data(layer1_offset + i, &buffer, isnew);
                bzero(layer1, sizeof(*layer1));
                layer1->phys_offset = HAMMER_BLOCKMAP_UNAVAIL;
                layer1->blocks_free = 0;
                hammer_crc_set_layer1(HammerVersion, layer1);
        }
        assert(i == HAMMER_BIGBLOCK_SIZE);
        rel_buffer(buffer);

        blockmap = &root_vol->ondisk->vol0_blockmap[HAMMER_ZONE_FREEMAP_INDEX];
        bzero(blockmap, sizeof(*blockmap));
        blockmap->phys_offset = layer1_offset;
        blockmap->first_offset = 0;
        blockmap->next_offset = HAMMER_ENCODE_RAW_BUFFER(0, 0);
        blockmap->alloc_offset = HAMMER_ENCODE_RAW_BUFFER(255, -1);
        hammer_crc_set_blockmap(HammerVersion, blockmap);
}

/*
 * Load the volume's remaining free space into the freemap.
 *
 * Returns the number of big-blocks available.
 */
int64_t
initialize_freemap(struct volume_info *volume)
{
        struct volume_info *root_vol;
        struct buffer_info *buffer1 = NULL;
        struct buffer_info *buffer2 = NULL;
        hammer_blockmap_layer1_t layer1;
        hammer_blockmap_layer2_t layer2;
        hammer_off_t layer1_offset;
        hammer_off_t layer2_offset;
        hammer_off_t phys_offset;
        hammer_off_t block_offset;
        hammer_off_t aligned_vol_free_end;
        hammer_blockmap_t freemap;
        int64_t count = 0;
        int64_t layer1_count = 0;

        root_vol = get_root_volume();

        assert_volume_offset(volume);
        aligned_vol_free_end = HAMMER_BLOCKMAP_LAYER2_DOALIGN(volume->vol_free_end);

        printf("initialize freemap volume %d\n", volume->vol_no);

        /*
         * Initialize the freemap.  First preallocate the big-blocks required
         * to implement layer2.   This preallocation is a bootstrap allocation
         * using blocks from the target volume.
         */
        freemap = &root_vol->ondisk->vol0_blockmap[HAMMER_ZONE_FREEMAP_INDEX];

        for (phys_offset = HAMMER_ENCODE_RAW_BUFFER(volume->vol_no, 0);
             phys_offset < aligned_vol_free_end;
             phys_offset += HAMMER_BLOCKMAP_LAYER2) {
                layer1_offset = freemap->phys_offset +
                                HAMMER_BLOCKMAP_LAYER1_OFFSET(phys_offset);
                layer1 = get_buffer_data(layer1_offset, &buffer1, 0);
                if (layer1->phys_offset == HAMMER_BLOCKMAP_UNAVAIL) {
                        layer1->phys_offset = bootstrap_bigblock(volume);
                        layer1->blocks_free = 0;
                        buffer1->cache.modified = 1;
                        hammer_crc_set_layer1(HammerVersion, layer1);
                }
        }

        /*
         * Now fill everything in.
         */
        for (phys_offset = HAMMER_ENCODE_RAW_BUFFER(volume->vol_no, 0);
             phys_offset < aligned_vol_free_end;
             phys_offset += HAMMER_BLOCKMAP_LAYER2) {
                layer1_count = 0;
                layer1_offset = freemap->phys_offset +
                                HAMMER_BLOCKMAP_LAYER1_OFFSET(phys_offset);
                layer1 = get_buffer_data(layer1_offset, &buffer1, 0);
                assert(layer1->phys_offset != HAMMER_BLOCKMAP_UNAVAIL);

                for (block_offset = 0;
                     block_offset < HAMMER_BLOCKMAP_LAYER2;
                     block_offset += HAMMER_BIGBLOCK_SIZE) {
                        layer2_offset = layer1->phys_offset +
                                        HAMMER_BLOCKMAP_LAYER2_OFFSET(block_offset);
                        layer2 = get_buffer_data(layer2_offset, &buffer2, 0);
                        bzero(layer2, sizeof(*layer2));

                        if (phys_offset + block_offset < volume->vol_free_off) {
                                /*
                                 * Big-blocks already allocated as part
                                 * of the freemap bootstrap.
                                 */
                                layer2->zone = HAMMER_ZONE_FREEMAP_INDEX;
                                layer2->append_off = HAMMER_BIGBLOCK_SIZE;
                                layer2->bytes_free = 0;
                        } else if (phys_offset + block_offset < volume->vol_free_end) {
                                layer2->zone = 0;
                                layer2->append_off = 0;
                                layer2->bytes_free = HAMMER_BIGBLOCK_SIZE;
                                ++count;
                                ++layer1_count;
                        } else {
                                layer2->zone = HAMMER_ZONE_UNAVAIL_INDEX;
                                layer2->append_off = HAMMER_BIGBLOCK_SIZE;
                                layer2->bytes_free = 0;
                        }
                        hammer_crc_set_layer2(HammerVersion, layer2);
                        buffer2->cache.modified = 1;
                }

                layer1->blocks_free += layer1_count;
                hammer_crc_set_layer1(HammerVersion, layer1);
                buffer1->cache.modified = 1;
        }

        rel_buffer(buffer1);
        rel_buffer(buffer2);
        return(count);
}

/*
 * Returns the number of big-blocks available for filesystem data and undos
 * without formatting.
 */
int64_t
count_freemap(struct volume_info *volume)
{
        hammer_off_t phys_offset;
        hammer_off_t vol_free_off;
        hammer_off_t aligned_vol_free_end;
        int64_t count = 0;

        vol_free_off = HAMMER_ENCODE_RAW_BUFFER(volume->vol_no, 0);

        assert_volume_offset(volume);
        aligned_vol_free_end = HAMMER_BLOCKMAP_LAYER2_DOALIGN(volume->vol_free_end);

        if (volume->vol_no == HAMMER_ROOT_VOLNO)
                vol_free_off += HAMMER_BIGBLOCK_SIZE;

        for (phys_offset = HAMMER_ENCODE_RAW_BUFFER(volume->vol_no, 0);
             phys_offset < aligned_vol_free_end;
             phys_offset += HAMMER_BLOCKMAP_LAYER2) {
                vol_free_off += HAMMER_BIGBLOCK_SIZE;
        }

        for (phys_offset = HAMMER_ENCODE_RAW_BUFFER(volume->vol_no, 0);
             phys_offset < aligned_vol_free_end;
             phys_offset += HAMMER_BIGBLOCK_SIZE) {
                if (phys_offset < vol_free_off)
                        ;
                else if (phys_offset < volume->vol_free_end)
                        ++count;
        }

        return(count);
}

/*
 * Format the undomap for the root volume.
 */
void
format_undomap(struct volume_info *root_vol, int64_t *undo_buffer_size)
{
        hammer_off_t undo_limit;
        hammer_blockmap_t blockmap;
        hammer_volume_ondisk_t ondisk;
        struct buffer_info *buffer = NULL;
        hammer_off_t scan;
        int n;
        int limit_index;
        uint32_t seqno;

        /* Only root volume needs formatting */
        assert(root_vol->vol_no == HAMMER_ROOT_VOLNO);
        ondisk = root_vol->ondisk;

        /*
         * Size the undo buffer in multiples of HAMMER_BIGBLOCK_SIZE,
         * up to HAMMER_MAX_UNDO_BIGBLOCKS big-blocks.
         * Size to approximately 0.1% of the disk.
         *
         * The minimum UNDO fifo size is 512MB, or approximately 1% of
         * the recommended 50G disk.
         *
         * Changing this minimum is rather dangerous as complex filesystem
         * operations can cause the UNDO FIFO to fill up otherwise.
         */
        undo_limit = *undo_buffer_size;
        if (undo_limit == 0) {
                undo_limit = HAMMER_VOL_BUF_SIZE(ondisk) / 1000;
                if (undo_limit < HAMMER_BIGBLOCK_SIZE * HAMMER_MIN_UNDO_BIGBLOCKS)
                        undo_limit = HAMMER_BIGBLOCK_SIZE * HAMMER_MIN_UNDO_BIGBLOCKS;
        }
        undo_limit = HAMMER_BIGBLOCK_DOALIGN(undo_limit);
        if (undo_limit < HAMMER_BIGBLOCK_SIZE)
                undo_limit = HAMMER_BIGBLOCK_SIZE;
        if (undo_limit > HAMMER_BIGBLOCK_SIZE * HAMMER_MAX_UNDO_BIGBLOCKS)
                undo_limit = HAMMER_BIGBLOCK_SIZE * HAMMER_MAX_UNDO_BIGBLOCKS;
        *undo_buffer_size = undo_limit;

        blockmap = &ondisk->vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
        bzero(blockmap, sizeof(*blockmap));
        blockmap->phys_offset = HAMMER_BLOCKMAP_UNAVAIL;
        blockmap->first_offset = HAMMER_ENCODE_UNDO(0);
        blockmap->next_offset = blockmap->first_offset;
        blockmap->alloc_offset = HAMMER_ENCODE_UNDO(undo_limit);
        hammer_crc_set_blockmap(HammerVersion, blockmap);

        limit_index = undo_limit / HAMMER_BIGBLOCK_SIZE;
        assert(limit_index <= HAMMER_MAX_UNDO_BIGBLOCKS);

        for (n = 0; n < limit_index; ++n)
                ondisk->vol0_undo_array[n] = alloc_undo_bigblock(root_vol);
        while (n < HAMMER_MAX_UNDO_BIGBLOCKS)
                ondisk->vol0_undo_array[n++] = HAMMER_BLOCKMAP_UNAVAIL;

        /*
         * Pre-initialize the UNDO blocks (HAMMER version 4+)
         */
        printf("initializing the undo map (%jd MB)\n",
                (intmax_t)HAMMER_OFF_LONG_ENCODE(blockmap->alloc_offset) /
                (1024 * 1024));

        scan = blockmap->first_offset;
        seqno = 0;

        while (scan < blockmap->alloc_offset) {
                hammer_fifo_head_t head;
                hammer_fifo_tail_t tail;
                int isnew;
                int bytes = HAMMER_UNDO_ALIGN;

                isnew = ((scan & HAMMER_BUFMASK64) == 0);
                head = get_buffer_data(scan, &buffer, isnew);
                buffer->cache.modified = 1;
                tail = (void *)((char *)head + bytes - sizeof(*tail));

                bzero(head, bytes);
                head->hdr_signature = HAMMER_HEAD_SIGNATURE;
                head->hdr_type = HAMMER_HEAD_TYPE_DUMMY;
                head->hdr_size = bytes;
                head->hdr_seq = seqno++;

                tail->tail_signature = HAMMER_TAIL_SIGNATURE;
                tail->tail_type = HAMMER_HEAD_TYPE_DUMMY;
                tail->tail_size = bytes;

                hammer_crc_set_fifo_head(HammerVersion, head, bytes);

                scan += bytes;
        }
        rel_buffer(buffer);
}

const char *zone_labels[] = {
        "",             /* 0 */
        "raw_volume",   /* 1 */
        "raw_buffer",   /* 2 */
        "undo",         /* 3 */
        "freemap",      /* 4 */
        "",             /* 5 */
        "",             /* 6 */
        "",             /* 7 */
        "btree",        /* 8 */
        "meta",         /* 9 */
        "large_data",   /* 10 */
        "small_data",   /* 11 */
        "",             /* 12 */
        "",             /* 13 */
        "",             /* 14 */
        "unavail",      /* 15 */
};

void
print_blockmap(const struct volume_info *volume)
{
        hammer_blockmap_t blockmap;
        hammer_volume_ondisk_t ondisk;
        int64_t size, used;
        int i;
#define INDENT ""

        ondisk = volume->ondisk;
        printf(INDENT"vol_label\t%s\n", ondisk->vol_label);
        printf(INDENT"vol_count\t%d\n", ondisk->vol_count);
        printf(INDENT"vol_bot_beg\t%s\n", sizetostr(ondisk->vol_bot_beg));
        printf(INDENT"vol_mem_beg\t%s\n", sizetostr(ondisk->vol_mem_beg));
        printf(INDENT"vol_buf_beg\t%s\n", sizetostr(ondisk->vol_buf_beg));
        printf(INDENT"vol_buf_end\t%s\n", sizetostr(ondisk->vol_buf_end));
        printf(INDENT"vol0_next_tid\t%016jx\n",
               (uintmax_t)ondisk->vol0_next_tid);

        blockmap = &ondisk->vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
        size = HAMMER_OFF_LONG_ENCODE(blockmap->alloc_offset);
        if (blockmap->first_offset <= blockmap->next_offset)
                used = blockmap->next_offset - blockmap->first_offset;
        else
                used = blockmap->alloc_offset - blockmap->first_offset +
                        HAMMER_OFF_LONG_ENCODE(blockmap->next_offset);
        printf(INDENT"undo_size\t%s\n", sizetostr(size));
        printf(INDENT"undo_used\t%s\n", sizetostr(used));

        printf(INDENT"zone #             "
               "phys             first            next             alloc\n");
        for (i = 0; i < HAMMER_MAX_ZONES; i++) {
                blockmap = &ondisk->vol0_blockmap[i];
                printf(INDENT"zone %-2d %-10s %016jx %016jx %016jx %016jx\n",
                        i, zone_labels[i],
                        (uintmax_t)blockmap->phys_offset,
                        (uintmax_t)blockmap->first_offset,
                        (uintmax_t)blockmap->next_offset,
                        (uintmax_t)blockmap->alloc_offset);
        }
}

/*
 * Flush various tracking structures to disk
 */
void
flush_all_volumes(void)
{
        struct volume_info *volume;

        TAILQ_FOREACH(volume, &VolList, entry)
                flush_volume(volume);
}

void
flush_volume(struct volume_info *volume)
{
        struct buffer_info *buffer;
        int i;

        for (i = 0; i < HAMMER_BUFLISTS; ++i) {
                TAILQ_FOREACH(buffer, &volume->buffer_lists[i], entry)
                        flush_buffer(buffer);
        }
        if (writehammervol(volume) == -1)
                err(1, "Write volume %d (%s)", volume->vol_no, volume->name);
}

void
flush_buffer(struct buffer_info *buffer)
{
        struct volume_info *volume;

        volume = buffer->volume;
        if (writehammerbuf(buffer) == -1)
                err(1, "Write volume %d (%s)", volume->vol_no, volume->name);
        buffer->cache.modified = 0;
}

/*
 * Core I/O operations
 */
static int
__read(struct volume_info *volume, void *data, int64_t offset, int size)
{
        ssize_t n;

        n = pread(volume->fd, data, size, offset);
        if (n != size)
                return(-1);
        return(0);
}

static __inline int
readhammervol(struct volume_info *volume)
{
        return(__read(volume, volume->ondisk, 0, HAMMER_BUFSIZE));
}

static __inline int
readhammerbuf(struct buffer_info *buffer)
{
        return(__read(buffer->volume, buffer->ondisk, buffer->raw_offset,
                HAMMER_BUFSIZE));
}

static int
__write(struct volume_info *volume, const void *data, int64_t offset, int size)
{
        ssize_t n;

        if (volume->rdonly)
                return(0);

        n = pwrite(volume->fd, data, size, offset);
        if (n != size)
                return(-1);
        return(0);
}

static __inline int
writehammervol(struct volume_info *volume)
{
        return(__write(volume, volume->ondisk, 0, HAMMER_BUFSIZE));
}

static __inline int
writehammerbuf(struct buffer_info *buffer)
{
        return(__write(buffer->volume, buffer->ondisk, buffer->raw_offset,
                HAMMER_BUFSIZE));
}

int64_t init_boot_area_size(int64_t value, off_t avg_vol_size)
{
        if (value == 0) {
                value = HAMMER_BOOT_NOMBYTES;
                while (value > avg_vol_size / HAMMER_MAX_VOLUMES)
                        value >>= 1;
        }

        if (value < HAMMER_BOOT_MINBYTES)
                value = HAMMER_BOOT_MINBYTES;
        else if (value > HAMMER_BOOT_MAXBYTES)
                value = HAMMER_BOOT_MAXBYTES;

        return(value);
}

int64_t init_memory_log_size(int64_t value, off_t avg_vol_size)
{
        if (value == 0) {
                value = HAMMER_MEM_NOMBYTES;
                while (value > avg_vol_size / HAMMER_MAX_VOLUMES)
                        value >>= 1;
        }

        if (value < HAMMER_MEM_MINBYTES)
                value = HAMMER_MEM_MINBYTES;
        else if (value > HAMMER_MEM_MAXBYTES)
                value = HAMMER_MEM_MAXBYTES;

        return(value);
}