2 * Copyright (c) 2009 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com> and
6 * Michael Neumann <mneumann@ntecs.de>
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
18 * 3. Neither the name of The DragonFly Project nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific, prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
28 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
29 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
31 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 #include <sys/fcntl.h>
39 #include <sys/nlookup.h>
45 hammer_setup_device(struct vnode **devvpp, const char *dev_path, int ronly);
48 hammer_close_device(struct vnode **devvpp, int ronly);
51 hammer_format_volume_header(struct hammer_mount *hmp, struct vnode *devvp,
52 const char *vol_name, int vol_no, int vol_count,
53 int64_t vol_size, int64_t boot_area_size, int64_t mem_area_size);
56 hammer_clear_volume_header(struct vnode *devvp);
58 struct bigblock_stat {
59 uint64_t total_bigblocks;
60 uint64_t total_free_bigblocks;
65 hammer_format_freemap(hammer_transaction_t trans, hammer_volume_t volume,
66 struct bigblock_stat *stat);
69 hammer_free_freemap(hammer_transaction_t trans, hammer_volume_t volume,
70 struct bigblock_stat *stat);
73 hammer_ioc_volume_add(hammer_transaction_t trans, hammer_inode_t ip,
74 struct hammer_ioc_volume *ioc)
76 struct hammer_mount *hmp = trans->hmp;
77 struct mount *mp = hmp->mp;
78 hammer_volume_t volume;
81 if (mp->mnt_flag & MNT_RDONLY) {
82 kprintf("Cannot add volume to read-only HAMMER filesystem\n");
86 if (hmp->nvolumes + 1 >= HAMMER_MAX_VOLUMES) {
87 kprintf("Max number of HAMMER volumes exceeded\n");
91 if (hammer_lock_ex_try(&hmp->volume_lock) != 0) {
92 kprintf("Another volume operation is in progress!\n");
97 * Find an unused volume number.
100 while (free_vol_no < HAMMER_MAX_VOLUMES &&
101 RB_LOOKUP(hammer_vol_rb_tree, &hmp->rb_vols_root, free_vol_no)) {
104 if (free_vol_no >= HAMMER_MAX_VOLUMES) {
105 kprintf("Max number of HAMMER volumes exceeded\n");
106 hammer_unlock(&hmp->volume_lock);
110 struct vnode *devvp = NULL;
111 error = hammer_setup_device(&devvp, ioc->device_name, 0);
115 error = hammer_format_volume_header(
118 hmp->rootvol->ondisk->vol_name,
124 hammer_close_device(&devvp, 0);
128 error = hammer_install_volume(hmp, ioc->device_name, NULL);
132 hammer_sync_lock_sh(trans);
133 hammer_lock_ex(&hmp->blkmap_lock);
138 * Set each volumes new value of the vol_count field.
140 for (int vol_no = 0; vol_no < HAMMER_MAX_VOLUMES; ++vol_no) {
141 volume = hammer_get_volume(hmp, vol_no, &error);
142 if (volume == NULL && error == ENOENT) {
144 * Skip unused volume numbers
149 KKASSERT(volume != NULL && error == 0);
150 hammer_modify_volume_field(trans, volume, vol_count);
151 volume->ondisk->vol_count = hmp->nvolumes;
152 hammer_modify_volume_done(volume);
155 * Only changes to the header of the root volume
156 * are automatically flushed to disk. For all
157 * other volumes that we modify we do it here.
159 * No interlock is needed, volume buffers are not
160 * messed with by bioops.
162 if (volume != trans->rootvol && volume->io.modified) {
163 hammer_crc_set_volume(volume->ondisk);
164 hammer_io_flush(&volume->io, 0);
167 hammer_rel_volume(volume, 0);
170 volume = hammer_get_volume(hmp, free_vol_no, &error);
171 KKASSERT(volume != NULL && error == 0);
173 struct bigblock_stat stat;
174 error = hammer_format_freemap(trans, volume, &stat);
175 KKASSERT(error == 0);
178 * Increase the total number of bigblocks
180 hammer_modify_volume_field(trans, trans->rootvol,
181 vol0_stat_bigblocks);
182 trans->rootvol->ondisk->vol0_stat_bigblocks += stat.total_bigblocks;
183 hammer_modify_volume_done(trans->rootvol);
186 * Increase the number of free bigblocks
187 * (including the copy in hmp)
189 hammer_modify_volume_field(trans, trans->rootvol,
190 vol0_stat_freebigblocks);
191 trans->rootvol->ondisk->vol0_stat_freebigblocks += stat.total_free_bigblocks;
192 hmp->copy_stat_freebigblocks =
193 trans->rootvol->ondisk->vol0_stat_freebigblocks;
194 hammer_modify_volume_done(trans->rootvol);
196 hammer_rel_volume(volume, 0);
198 hammer_unlock(&hmp->blkmap_lock);
199 hammer_sync_unlock(trans);
201 KKASSERT(error == 0);
203 hammer_unlock(&hmp->volume_lock);
205 kprintf("An error occurred: %d\n", error);
214 hammer_ioc_volume_del(hammer_transaction_t trans, hammer_inode_t ip,
215 struct hammer_ioc_volume *ioc)
217 struct hammer_mount *hmp = trans->hmp;
218 struct mount *mp = hmp->mp;
219 hammer_volume_t volume;
222 if (mp->mnt_flag & MNT_RDONLY) {
223 kprintf("Cannot del volume from read-only HAMMER filesystem\n");
227 if (hammer_lock_ex_try(&hmp->volume_lock) != 0) {
228 kprintf("Another volume operation is in progress!\n");
235 * find volume by volname
237 for (int vol_no = 0; vol_no < HAMMER_MAX_VOLUMES; ++vol_no) {
238 volume = hammer_get_volume(hmp, vol_no, &error);
239 if (volume == NULL && error == ENOENT) {
241 * Skip unused volume numbers
246 KKASSERT(volume != NULL && error == 0);
247 if (strcmp(volume->vol_name, ioc->device_name) == 0) {
250 hammer_rel_volume(volume, 0);
254 if (volume == NULL) {
255 kprintf("Couldn't find volume\n");
260 if (volume == trans->rootvol) {
261 kprintf("Cannot remove root-volume\n");
262 hammer_rel_volume(volume, 0);
271 hmp->volume_to_remove = volume->vol_no;
273 struct hammer_ioc_reblock reblock;
274 bzero(&reblock, sizeof(reblock));
276 reblock.key_beg.localization = HAMMER_MIN_LOCALIZATION;
277 reblock.key_beg.obj_id = HAMMER_MIN_OBJID;
278 reblock.key_end.localization = HAMMER_MAX_LOCALIZATION;
279 reblock.key_end.obj_id = HAMMER_MAX_OBJID;
280 reblock.head.flags = HAMMER_IOC_DO_FLAGS;
281 reblock.free_level = 0;
283 error = hammer_ioc_reblock(trans, ip, &reblock);
285 if (reblock.head.flags & HAMMER_IOC_HEAD_INTR) {
290 if (error == EINTR) {
291 kprintf("reblock was interrupted\n");
293 kprintf("reblock failed: %d\n", error);
295 hmp->volume_to_remove = -1;
296 hammer_rel_volume(volume, 0);
304 while (hammer_flusher_haswork(hmp)) {
305 hammer_flusher_sync(hmp);
309 kprintf("HAMMER: flushing.");
312 tsleep(&count, 0, "hmrufl", hz);
315 kprintf("giving up");
321 hammer_sync_lock_sh(trans);
322 hammer_lock_ex(&hmp->blkmap_lock);
325 * We use stat later to update rootvol's bigblock stats
327 struct bigblock_stat stat;
328 error = hammer_free_freemap(trans, volume, &stat);
330 kprintf("Failed to free volume. Volume not empty!\n");
331 hmp->volume_to_remove = -1;
332 hammer_rel_volume(volume, 0);
333 hammer_unlock(&hmp->blkmap_lock);
334 hammer_sync_unlock(trans);
338 hmp->volume_to_remove = -1;
340 hammer_rel_volume(volume, 0);
345 RB_SCAN(hammer_buf_rb_tree, &hmp->rb_bufs_root, NULL,
346 hammer_unload_buffer, volume);
348 error = hammer_unload_volume(volume, NULL);
350 kprintf("Failed to unload volume\n");
351 hammer_unlock(&hmp->blkmap_lock);
352 hammer_sync_unlock(trans);
360 * Set each volume's new value of the vol_count field.
362 for (int vol_no = 0; vol_no < HAMMER_MAX_VOLUMES; ++vol_no) {
363 volume = hammer_get_volume(hmp, vol_no, &error);
364 if (volume == NULL && error == ENOENT) {
366 * Skip unused volume numbers
372 KKASSERT(volume != NULL && error == 0);
373 hammer_modify_volume_field(trans, volume, vol_count);
374 volume->ondisk->vol_count = hmp->nvolumes;
375 hammer_modify_volume_done(volume);
378 * Only changes to the header of the root volume
379 * are automatically flushed to disk. For all
380 * other volumes that we modify we do it here.
382 * No interlock is needed, volume buffers are not
383 * messed with by bioops.
385 if (volume != trans->rootvol && volume->io.modified) {
386 hammer_crc_set_volume(volume->ondisk);
387 hammer_io_flush(&volume->io, 0);
390 hammer_rel_volume(volume, 0);
394 * Update the total number of bigblocks
396 hammer_modify_volume_field(trans, trans->rootvol,
397 vol0_stat_bigblocks);
398 trans->rootvol->ondisk->vol0_stat_bigblocks -= stat.total_bigblocks;
399 hammer_modify_volume_done(trans->rootvol);
402 * Update the number of free bigblocks
403 * (including the copy in hmp)
405 hammer_modify_volume_field(trans, trans->rootvol,
406 vol0_stat_freebigblocks);
407 trans->rootvol->ondisk->vol0_stat_freebigblocks -= stat.total_free_bigblocks;
408 hmp->copy_stat_freebigblocks =
409 trans->rootvol->ondisk->vol0_stat_freebigblocks;
410 hammer_modify_volume_done(trans->rootvol);
413 hammer_unlock(&hmp->blkmap_lock);
414 hammer_sync_unlock(trans);
417 * Erase the volume header of the removed device.
419 * This is to not accidentally mount the volume again.
421 struct vnode *devvp = NULL;
422 error = hammer_setup_device(&devvp, ioc->device_name, 0);
424 kprintf("Failed to open device: %s\n", ioc->device_name);
428 error = hammer_clear_volume_header(devvp);
430 kprintf("Failed to clear volume header of device: %s\n",
434 hammer_close_device(&devvp, 0);
436 KKASSERT(error == 0);
438 hammer_unlock(&hmp->volume_lock);
444 hammer_ioc_volume_list(hammer_transaction_t trans, hammer_inode_t ip,
445 struct hammer_ioc_volume_list *ioc)
447 struct hammer_mount *hmp = trans->hmp;
448 hammer_volume_t volume;
452 for (i = 0, cnt = 0; i < HAMMER_MAX_VOLUMES && cnt < ioc->nvols; i++) {
453 volume = hammer_get_volume(hmp, i, &error);
454 if (volume == NULL && error == ENOENT) {
458 KKASSERT(volume != NULL && error == 0);
460 len = strlen(volume->vol_name) + 1;
461 KKASSERT(len <= MAXPATHLEN);
463 error = copyout(volume->vol_name, ioc->vols[cnt].device_name,
466 hammer_rel_volume(volume, 0);
470 hammer_rel_volume(volume, 0);
478 * Iterate over all usable L1 entries of the volume and
479 * the corresponding L2 entries.
482 hammer_iterate_l1l2_entries(hammer_transaction_t trans, hammer_volume_t volume,
483 int (*callback)(hammer_transaction_t, hammer_volume_t, hammer_buffer_t*,
484 struct hammer_blockmap_layer1*, struct hammer_blockmap_layer2*,
485 hammer_off_t, hammer_off_t, void*),
488 struct hammer_mount *hmp = trans->hmp;
489 hammer_blockmap_t freemap = &hmp->blockmap[HAMMER_ZONE_FREEMAP_INDEX];
490 hammer_buffer_t buffer = NULL;
493 hammer_off_t phys_off;
494 hammer_off_t block_off;
495 hammer_off_t layer1_off;
496 hammer_off_t layer2_off;
497 hammer_off_t aligned_buf_end_off;
498 struct hammer_blockmap_layer1 *layer1;
499 struct hammer_blockmap_layer2 *layer2;
502 * Calculate the usable size of the volume, which
503 * must be aligned at a bigblock (8 MB) boundary.
505 aligned_buf_end_off = (HAMMER_ENCODE_RAW_BUFFER(volume->ondisk->vol_no,
506 (volume->ondisk->vol_buf_end - volume->ondisk->vol_buf_beg)
507 & ~HAMMER_LARGEBLOCK_MASK64));
510 * Iterate the volume's address space in chunks of 4 TB, where each
511 * chunk consists of at least one physically available 8 MB bigblock.
513 * For each chunk we need one L1 entry and one L2 bigblock.
514 * We use the first bigblock of each chunk as L2 block.
516 for (phys_off = HAMMER_ENCODE_RAW_BUFFER(volume->ondisk->vol_no, 0);
517 phys_off < aligned_buf_end_off;
518 phys_off += HAMMER_BLOCKMAP_LAYER2) {
520 block_off < HAMMER_BLOCKMAP_LAYER2;
521 block_off += HAMMER_LARGEBLOCK_SIZE) {
522 layer2_off = phys_off +
523 HAMMER_BLOCKMAP_LAYER2_OFFSET(block_off);
524 layer2 = hammer_bread(hmp, layer2_off, &error, &buffer);
528 error = callback(trans, volume, &buffer, NULL,
529 layer2, phys_off, block_off, data);
534 layer1_off = freemap->phys_offset +
535 HAMMER_BLOCKMAP_LAYER1_OFFSET(phys_off);
536 layer1 = hammer_bread(hmp, layer1_off, &error, &buffer);
540 error = callback(trans, volume, &buffer, layer1, NULL,
548 hammer_rel_buffer(buffer, 0);
557 format_callback(hammer_transaction_t trans, hammer_volume_t volume,
558 hammer_buffer_t *bufferp,
559 struct hammer_blockmap_layer1 *layer1,
560 struct hammer_blockmap_layer2 *layer2,
561 hammer_off_t phys_off,
562 hammer_off_t block_off,
565 struct bigblock_stat *stat = (struct bigblock_stat*)data;
568 * Calculate the usable size of the volume, which must be aligned
569 * at a bigblock (8 MB) boundary.
571 hammer_off_t aligned_buf_end_off;
572 aligned_buf_end_off = (HAMMER_ENCODE_RAW_BUFFER(volume->ondisk->vol_no,
573 (volume->ondisk->vol_buf_end - volume->ondisk->vol_buf_beg)
574 & ~HAMMER_LARGEBLOCK_MASK64));
577 KKASSERT(layer1->phys_offset == HAMMER_BLOCKMAP_UNAVAIL);
579 hammer_modify_buffer(trans, *bufferp, layer1, sizeof(*layer1));
580 bzero(layer1, sizeof(*layer1));
581 layer1->phys_offset = phys_off;
582 layer1->blocks_free = stat->counter;
583 layer1->layer1_crc = crc32(layer1, HAMMER_LAYER1_CRCSIZE);
584 hammer_modify_buffer_done(*bufferp);
586 stat->total_free_bigblocks += stat->counter;
587 stat->counter = 0; /* reset */
589 hammer_modify_buffer(trans, *bufferp, layer2, sizeof(*layer2));
590 bzero(layer2, sizeof(*layer2));
592 if (block_off == 0) {
594 * The first entry represents the L2 bigblock itself.
596 layer2->zone = HAMMER_ZONE_FREEMAP_INDEX;
597 layer2->append_off = HAMMER_LARGEBLOCK_SIZE;
598 layer2->bytes_free = 0;
599 ++stat->total_bigblocks;
600 } else if (phys_off + block_off < aligned_buf_end_off) {
605 layer2->append_off = 0;
606 layer2->bytes_free = HAMMER_LARGEBLOCK_SIZE;
607 ++stat->total_bigblocks;
611 * Bigblock outside of physically available
614 layer2->zone = HAMMER_ZONE_UNAVAIL_INDEX;
615 layer2->append_off = HAMMER_LARGEBLOCK_SIZE;
616 layer2->bytes_free = 0;
619 layer2->entry_crc = crc32(layer2, HAMMER_LAYER2_CRCSIZE);
620 hammer_modify_buffer_done(*bufferp);
629 hammer_format_freemap(hammer_transaction_t trans, hammer_volume_t volume,
630 struct bigblock_stat *stat)
632 stat->total_bigblocks = 0;
633 stat->total_free_bigblocks = 0;
635 return hammer_iterate_l1l2_entries(trans, volume, format_callback, stat);
639 free_callback(hammer_transaction_t trans, hammer_volume_t volume __unused,
640 hammer_buffer_t *bufferp,
641 struct hammer_blockmap_layer1 *layer1,
642 struct hammer_blockmap_layer2 *layer2,
643 hammer_off_t phys_off,
644 hammer_off_t block_off __unused,
647 struct bigblock_stat *stat = (struct bigblock_stat*)data;
650 * No modifications to ondisk structures
652 int testonly = (stat == NULL);
655 if (layer1->phys_offset == HAMMER_BLOCKMAP_UNAVAIL) {
657 * This layer1 entry is already free.
662 KKASSERT((int)HAMMER_VOL_DECODE(layer1->phys_offset) ==
663 trans->hmp->volume_to_remove);
671 hammer_modify_buffer(trans, *bufferp, layer1, sizeof(*layer1));
672 bzero(layer1, sizeof(*layer1));
673 layer1->phys_offset = HAMMER_BLOCKMAP_UNAVAIL;
674 layer1->layer1_crc = crc32(layer1, HAMMER_LAYER1_CRCSIZE);
675 hammer_modify_buffer_done(*bufferp);
679 if (layer2->zone == HAMMER_ZONE_UNAVAIL_INDEX) {
683 if (layer2->zone == HAMMER_ZONE_FREEMAP_INDEX) {
685 ++stat->total_bigblocks;
690 if (layer2->append_off == 0 &&
691 layer2->bytes_free == HAMMER_LARGEBLOCK_SIZE) {
693 ++stat->total_bigblocks;
694 ++stat->total_free_bigblocks;
700 * We found a layer2 entry that is not empty!
711 hammer_free_freemap(hammer_transaction_t trans, hammer_volume_t volume,
712 struct bigblock_stat *stat)
716 stat->total_bigblocks = 0;
717 stat->total_free_bigblocks = 0;
720 error = hammer_iterate_l1l2_entries(trans, volume, free_callback, NULL);
724 error = hammer_iterate_l1l2_entries(trans, volume, free_callback, stat);
728 /************************************************************************
730 ************************************************************************
734 hammer_setup_device(struct vnode **devvpp, const char *dev_path, int ronly)
737 struct nlookupdata nd;
740 * Get the device vnode
742 if (*devvpp == NULL) {
743 error = nlookup_init(&nd, dev_path, UIO_SYSSPACE, NLC_FOLLOW);
745 error = nlookup(&nd);
747 error = cache_vref(&nd.nl_nch, nd.nl_cred, devvpp);
754 if (vn_isdisk(*devvpp, &error)) {
755 error = vfs_mountedon(*devvpp);
758 if (error == 0 && vcount(*devvpp) > 0)
761 vn_lock(*devvpp, LK_EXCLUSIVE | LK_RETRY);
762 error = vinvalbuf(*devvpp, V_SAVE, 0, 0);
764 error = VOP_OPEN(*devvpp,
765 (ronly ? FREAD : FREAD|FWRITE),
770 if (error && *devvpp) {
778 hammer_close_device(struct vnode **devvpp, int ronly)
781 vinvalbuf(*devvpp, ronly ? 0 : V_SAVE, 0, 0);
782 VOP_CLOSE(*devvpp, (ronly ? FREAD : FREAD|FWRITE));
789 hammer_format_volume_header(struct hammer_mount *hmp, struct vnode *devvp,
790 const char *vol_name, int vol_no, int vol_count,
791 int64_t vol_size, int64_t boot_area_size, int64_t mem_area_size)
793 struct buf *bp = NULL;
794 struct hammer_volume_ondisk *ondisk;
798 * Extract the volume number from the volume header and do various
801 KKASSERT(HAMMER_BUFSIZE >= sizeof(struct hammer_volume_ondisk));
802 error = bread(devvp, 0LL, HAMMER_BUFSIZE, &bp);
803 if (error || bp->b_bcount < sizeof(struct hammer_volume_ondisk))
806 ondisk = (struct hammer_volume_ondisk*) bp->b_data;
809 * Note that we do NOT allow to use a device that contains
810 * a valid HAMMER signature. It has to be cleaned up with dd
813 if (ondisk->vol_signature == HAMMER_FSBUF_VOLUME) {
814 kprintf("hammer_volume_add: Formatting of valid HAMMER volume "
815 "%s denied. Erase with dd!\n", vol_name);
820 bzero(ondisk, sizeof(struct hammer_volume_ondisk));
821 ksnprintf(ondisk->vol_name, sizeof(ondisk->vol_name), "%s", vol_name);
822 ondisk->vol_fstype = hmp->rootvol->ondisk->vol_fstype;
823 ondisk->vol_signature = HAMMER_FSBUF_VOLUME;
824 ondisk->vol_fsid = hmp->fsid;
825 ondisk->vol_rootvol = hmp->rootvol->vol_no;
826 ondisk->vol_no = vol_no;
827 ondisk->vol_count = vol_count;
828 ondisk->vol_version = hmp->version;
831 * Reserve space for (future) header junk, setup our poor-man's
832 * bigblock allocator.
834 int64_t vol_alloc = HAMMER_BUFSIZE * 16;
836 ondisk->vol_bot_beg = vol_alloc;
837 vol_alloc += boot_area_size;
838 ondisk->vol_mem_beg = vol_alloc;
839 vol_alloc += mem_area_size;
842 * The remaining area is the zone 2 buffer allocation area. These
845 ondisk->vol_buf_beg = vol_alloc;
846 ondisk->vol_buf_end = vol_size & ~(int64_t)HAMMER_BUFMASK;
848 if (ondisk->vol_buf_end < ondisk->vol_buf_beg) {
849 kprintf("volume %d %s is too small to hold the volume header",
850 ondisk->vol_no, ondisk->vol_name);
855 ondisk->vol_nblocks = (ondisk->vol_buf_end - ondisk->vol_buf_beg) /
857 ondisk->vol_blocksize = HAMMER_BUFSIZE;
860 * Write volume header to disk
872 * Invalidates the volume header. Used by volume-del.
875 hammer_clear_volume_header(struct vnode *devvp)
877 struct buf *bp = NULL;
878 struct hammer_volume_ondisk *ondisk;
881 KKASSERT(HAMMER_BUFSIZE >= sizeof(struct hammer_volume_ondisk));
882 error = bread(devvp, 0LL, HAMMER_BUFSIZE, &bp);
883 if (error || bp->b_bcount < sizeof(struct hammer_volume_ondisk))
886 ondisk = (struct hammer_volume_ondisk*) bp->b_data;
887 bzero(ondisk, sizeof(struct hammer_volume_ondisk));