/*
 * Copyright (c) 2013-2019 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@dragonflybsd.org>
 *
 * 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/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>

#include "hammer2.h"

/*
 * breadth-first search
 */
typedef struct hammer2_chain_save {
	TAILQ_ENTRY(hammer2_chain_save)	entry;
	hammer2_chain_t	*chain;
} hammer2_chain_save_t;

TAILQ_HEAD(hammer2_chain_save_list, hammer2_chain_save);
typedef struct hammer2_chain_save_list hammer2_chain_save_list_t;

typedef struct hammer2_bulkfree_info {
	hammer2_dev_t		*hmp;
	kmem_anon_desc_t	kp;
	hammer2_off_t		sbase;		/* sub-loop iteration */
	hammer2_off_t		sstop;
	hammer2_bmap_data_t	*bmap;
	int			depth;
	long			count_10_00;	/* staged->free	     */
	long			count_11_10;	/* allocated->staged */
	long			count_00_11;	/* (should not happen) */
	long			count_01_11;	/* (should not happen) */
	long			count_10_11;	/* staged->allocated */
	long			count_l0cleans;
	long			count_linadjusts;
	long			count_inodes_scanned;
	long			count_dirents_scanned;
	long			count_dedup_factor;
	long			count_bytes_scanned;
	long			count_chains_scanned;
	long			count_chains_reported;
	long			bulkfree_calls;
	int			bulkfree_ticks;
	int			list_alert;
	hammer2_off_t		adj_free;
	hammer2_tid_t		mtid;
	time_t			save_time;
	hammer2_chain_save_list_t list;
	long			list_count;
	long			list_count_max;
	hammer2_chain_save_t	*backout;	/* ins pt while backing out */
	hammer2_dedup_t		*dedup;
	int			pri;
} hammer2_bulkfree_info_t;

static int h2_bulkfree_test(hammer2_bulkfree_info_t *info,
			hammer2_blockref_t *bref, int pri, int saved_error);
static uint32_t bigmask_get(hammer2_bmap_data_t *bmap);
static int bigmask_good(hammer2_bmap_data_t *bmap, uint32_t live_bigmask);

/*
 * General bulk scan function with callback.  Called with a referenced
 * but UNLOCKED parent.  The parent is returned in the same state.
 */
static
int
hammer2_bulkfree_scan(hammer2_chain_t *parent,
		  int (*func)(hammer2_bulkfree_info_t *info,
			      hammer2_blockref_t *bref),
		  hammer2_bulkfree_info_t *info)
{
	hammer2_blockref_t bref;
	hammer2_chain_t *chain;
	hammer2_chain_save_t *tail;
	hammer2_chain_save_t *save;
	int first = 1;
	int rup_error;
	int error;
	int e2;

	++info->pri;

	chain = NULL;
	rup_error = 0;
	error = 0;

	hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS |
				   HAMMER2_RESOLVE_SHARED);

	/*
	 * End of scan if parent is a PFS
	 */
	tail = TAILQ_FIRST(&info->list);

	/*
	 * The parent was previously retrieved NODATA and thus has not
	 * tested the CRC.  Now that we have locked it normally, check
	 * for a CRC problem and skip it if we found one.  The bulk scan
	 * cannot safely traverse invalid block tables (we could end up
	 * in an endless loop or cause a panic).
	 */
	if (parent->error & HAMMER2_ERROR_CHECK) {
		error = parent->error;
		goto done;
	}

	/*
	 * Report which PFS is being scanned
	 */
	if (parent->bref.type == HAMMER2_BREF_TYPE_INODE &&
	    (parent->bref.flags & HAMMER2_BREF_FLAG_PFSROOT)) {
		kprintf("hammer2_bulkfree: Scanning %s\n",
			parent->data->ipdata.filename);
	}

	/*
	 * Generally loop on the contents if we have not been flagged
	 * for abort.
	 *
	 * Remember that these chains are completely isolated from
	 * the frontend, so we can release locks temporarily without
	 * imploding.
	 */
	for (;;) {
		error |= hammer2_chain_scan(parent, &chain, &bref, &first,
					    HAMMER2_LOOKUP_NODATA |
					    HAMMER2_LOOKUP_SHARED);

		/*
		 * Handle EOF or other error at current level.  This stops
		 * the bulkfree scan.
		 */
		if (error & ~HAMMER2_ERROR_CHECK)
			break;

		/*
		 * Account for dirents before thre data_off test, since most
		 * dirents do not need a data reference.
		 */
		if (bref.type == HAMMER2_BREF_TYPE_DIRENT)
			++info->count_dirents_scanned;

		/*
		 * Ignore brefs without data (typically dirents)
		 */
		if ((bref.data_off & ~HAMMER2_OFF_MASK_RADIX) == 0)
			continue;

		/*
		 * Process bref, chain is only non-NULL if the bref
		 * might be recursable (its possible that we sometimes get
		 * a non-NULL chain where the bref cannot be recursed).
		 *
		 * If we already ran down this tree we do not have to do it
		 * again, but we must still recover any cumulative error
		 * recorded from the time we did.
		 */
		++info->pri;
		e2 = h2_bulkfree_test(info, &bref, 1, 0);
		if (e2) {
			error |= e2 & ~HAMMER2_ERROR_EOF;
			continue;
		}

		if (bref.type == HAMMER2_BREF_TYPE_INODE)
			++info->count_inodes_scanned;

		error |= func(info, &bref);
		if (error & ~HAMMER2_ERROR_CHECK)
			break;

		/*
		 * A non-null chain is always returned if it is
		 * recursive, otherwise a non-null chain might be
		 * returned but usually is not when not recursive.
		 */
		if (chain == NULL)
			continue;

		info->count_bytes_scanned += chain->bytes;
		++info->count_chains_scanned;

		if (info->count_chains_scanned >=
		    info->count_chains_reported + 1000000 ||
		    (info->count_chains_scanned < 1000000 &&
		     info->count_chains_scanned >=
		     info->count_chains_reported + 100000)) {
			kprintf(" chains %-7ld inodes %-7ld "
				"dirents %-7ld bytes %5ldMB\n",
				info->count_chains_scanned,
				info->count_inodes_scanned,
				info->count_dirents_scanned,
				info->count_bytes_scanned / 1000000);
			info->count_chains_reported =
				info->count_chains_scanned;
		}

		/*
		 * Else check type and setup depth-first scan.
		 *
		 * Account for bytes actually read.
		 */
		switch(chain->bref.type) {
		case HAMMER2_BREF_TYPE_INODE:
		case HAMMER2_BREF_TYPE_FREEMAP_NODE:
		case HAMMER2_BREF_TYPE_INDIRECT:
		case HAMMER2_BREF_TYPE_VOLUME:
		case HAMMER2_BREF_TYPE_FREEMAP:
			++info->depth;
			if (chain->error & HAMMER2_ERROR_CHECK) {
				/*
				 * Cannot safely recurse chains with crc
				 * errors, even in emergency mode.
				 */
				/* NOP */
			} else if (info->depth > 16 ||
				   info->backout ||
				   (info->depth > hammer2_limit_saved_depth &&
				   info->list_count >=
				    (hammer2_limit_saved_chains >> 2)))
			{
				/*
				 * We must defer the recursion if it runs
				 * too deep or if too many saved chains are
				 * allocated.
				 *
				 * In the case of too many saved chains, we
				 * have to stop recursing ASAP to avoid an
				 * explosion of memory use since each radix
				 * level can hold 512 elements.
				 *
				 * If we had to defer at a deeper level
				 * backout is non-NULL.  We must backout
				 * completely before resuming.
				 */
				if (info->list_count >
				     hammer2_limit_saved_chains &&
				    info->list_alert == 0)
				{
					kprintf("hammer2: during bulkfree, "
						"saved chains exceeded %ld "
						"at depth %d, "
						"backing off to less-efficient "
						"operation\n",
						hammer2_limit_saved_chains,
						info->depth);
					info->list_alert = 1;
				}

				/*
				 * Must be placed at head so pfsroot scan
				 * can exhaust saved elements for that pfs
				 * first.
				 *
				 * Must be placed at head for depth-first
				 * recovery when too many saved chains, to
				 * limit number of chains saved during
				 * saved-chain reruns.  The worst-case excess
				 * is (maximum_depth * 512) saved chains above
				 * the threshold.
				 *
				 * The maximum_depth generally occurs in the
				 * inode index and can be fairly deep once
				 * the radix tree becomes a bit fragmented.
				 * nominally 100M inodes would be only 4 deep,
				 * plus a maximally sized file would be another
				 * 8 deep, but with fragmentation it can wind
				 * up being a lot more.
				 *
				 * However, when backing out, we have to place
				 * all the entries in each parent node not
				 * yet processed on the list too, and because
				 * these entries are shallower they must be
				 * placed after each other in order to maintain
				 * our depth-first processing.
				 */
				save = kmalloc(sizeof(*save), M_HAMMER2,
					       M_WAITOK | M_ZERO);
				save->chain = chain;
				hammer2_chain_ref(chain);

				if (info->backout) {
					TAILQ_INSERT_AFTER(&info->list,
							   info->backout,
							   save, entry);
				} else {
					TAILQ_INSERT_HEAD(&info->list,
							  save, entry);
				}
				info->backout = save;
				++info->list_count;
				if (info->list_count_max < info->list_count)
					info->list_count_max = info->list_count;

				/* guess */
				info->pri += 10;
			} else {
				int savepri = info->pri;

				hammer2_chain_unlock(chain);
				hammer2_chain_unlock(parent);
				info->pri = 0;
				rup_error |= hammer2_bulkfree_scan(chain,
								   func, info);
				info->pri += savepri;
				hammer2_chain_lock(parent,
						   HAMMER2_RESOLVE_ALWAYS |
						   HAMMER2_RESOLVE_SHARED);
				hammer2_chain_lock(chain,
						   HAMMER2_RESOLVE_ALWAYS |
						   HAMMER2_RESOLVE_SHARED);
			}
			--info->depth;
			break;
		case HAMMER2_BREF_TYPE_DATA:
			break;
		default:
			/* does not recurse */
			break;
		}
		if (rup_error & HAMMER2_ERROR_ABORTED)
			break;
	}
	if (chain) {
		hammer2_chain_unlock(chain);
		hammer2_chain_drop(chain);
	}

	/*
	 * If this is a PFSROOT, also re-run any defered elements
	 * added during our scan so we can report any cumulative errors
	 * for the PFS.
	 */
	if (parent->bref.type == HAMMER2_BREF_TYPE_INODE &&
	    (parent->bref.flags & HAMMER2_BREF_FLAG_PFSROOT)) {
		for (;;) {
			int opri;

			save = TAILQ_FIRST(&info->list);
			if (save == tail)	/* exhaust this PFS only */
				break;

			TAILQ_REMOVE(&info->list, save, entry);
			info->backout = NULL;
			--info->list_count;
			opri = info->pri;
			info->pri = 0;
			rup_error |= hammer2_bulkfree_scan(save->chain, func, info);
			hammer2_chain_drop(save->chain);
			kfree(save, M_HAMMER2);
			info->pri = opri;
		}
	}

	error |= rup_error;

	/*
	 * Report which PFS the errors were encountered in.
	 */
	if (parent->bref.type == HAMMER2_BREF_TYPE_INODE &&
	    (parent->bref.flags & HAMMER2_BREF_FLAG_PFSROOT) &&
	    (error & ~HAMMER2_ERROR_EOF)) {
		kprintf("hammer2_bulkfree: Encountered errors (%08x) "
			"while scanning \"%s\"\n",
			error, parent->data->ipdata.filename);
	}

	/*
	 * Save with higher pri now that we know what it is.
	 */
	h2_bulkfree_test(info, &parent->bref, info->pri + 1,
			 (error & ~HAMMER2_ERROR_EOF));

done:
	hammer2_chain_unlock(parent);

	return (error & ~HAMMER2_ERROR_EOF);
}

/*
 * Bulkfree algorithm
 *
 * Repeat {
 *	Chain flush (partial synchronization) XXX removed
 *	Scan the whole topology - build in-memory freemap (mark 11)
 *	Reconcile the in-memory freemap against the on-disk freemap.
 *		ondisk xx -> ondisk 11 (if allocated)
 *		ondisk 11 -> ondisk 10 (if free in-memory)
 *		ondisk 10 -> ondisk 00 (if free in-memory) - on next pass
 * }
 *
 * The topology scan may have to be performed multiple times to window
 * freemaps which are too large to fit in kernel memory.
 *
 * Races are handled using a double-transition (11->10, 10->00).  The bulkfree
 * scan snapshots the volume root's blockset and thus can run concurrent with
 * normal operations, as long as a full flush is made between each pass to
 * synchronize any modified chains (otherwise their blocks might be improperly
 * freed).
 *
 * Temporary memory in multiples of 32KB is required to reconstruct the leaf
 * hammer2_bmap_data blocks so they can later be compared against the live
 * freemap.  Each 32KB represents 256 x 16KB x 256 = ~1 GB of storage.
 * A 32MB save area thus represents around ~1 TB.  The temporary memory
 * allocated can be specified.  If it is not sufficient multiple topology
 * passes will be made.
 */

/*
 * Bulkfree callback info
 */
static void hammer2_bulkfree_thread(void *arg __unused);
static void cbinfo_bmap_init(hammer2_bulkfree_info_t *cbinfo, size_t size);
static int h2_bulkfree_callback(hammer2_bulkfree_info_t *cbinfo,
			hammer2_blockref_t *bref);
static int h2_bulkfree_sync(hammer2_bulkfree_info_t *cbinfo);
static void h2_bulkfree_sync_adjust(hammer2_bulkfree_info_t *cbinfo,
			hammer2_off_t data_off, hammer2_bmap_data_t *live,
			hammer2_bmap_data_t *bmap, hammer2_key_t alloc_base);

void
hammer2_bulkfree_init(hammer2_dev_t *hmp)
{
	hammer2_thr_create(&hmp->bfthr, NULL, hmp,
			   hmp->devrepname, -1, -1,
			   hammer2_bulkfree_thread);
}

void
hammer2_bulkfree_uninit(hammer2_dev_t *hmp)
{
	hammer2_thr_delete(&hmp->bfthr);
}

static void
hammer2_bulkfree_thread(void *arg)
{
	hammer2_thread_t *thr = arg;
	hammer2_ioc_bulkfree_t bfi;
	uint32_t flags;

	for (;;) {
		hammer2_thr_wait_any(thr,
				     HAMMER2_THREAD_STOP |
				     HAMMER2_THREAD_FREEZE |
				     HAMMER2_THREAD_UNFREEZE |
				     HAMMER2_THREAD_REMASTER,
				     hz * 60);

		flags = thr->flags;
		cpu_ccfence();
		if (flags & HAMMER2_THREAD_STOP)
			break;
		if (flags & HAMMER2_THREAD_FREEZE) {
			hammer2_thr_signal2(thr, HAMMER2_THREAD_FROZEN,
						 HAMMER2_THREAD_FREEZE);
			continue;
		}
		if (flags & HAMMER2_THREAD_UNFREEZE) {
			hammer2_thr_signal2(thr, 0,
						 HAMMER2_THREAD_FROZEN |
						 HAMMER2_THREAD_UNFREEZE);
			continue;
		}
		if (flags & HAMMER2_THREAD_FROZEN)
			continue;
		if (flags & HAMMER2_THREAD_REMASTER) {
			hammer2_thr_signal2(thr, 0, HAMMER2_THREAD_REMASTER);
			bzero(&bfi, sizeof(bfi));
			bfi.size = 8192 * 1024;
			/* hammer2_bulkfree_pass(thr->hmp, &bfi); */
		}
	}
	thr->td = NULL;
	hammer2_thr_signal(thr, HAMMER2_THREAD_STOPPED);
	/* structure can go invalid at this point */
}

int
hammer2_bulkfree_pass(hammer2_dev_t *hmp, hammer2_chain_t *vchain,
		      hammer2_ioc_bulkfree_t *bfi)
{
	hammer2_bulkfree_info_t cbinfo;
	hammer2_chain_save_t *save;
	hammer2_off_t incr;
	size_t size;
	int error;

	/*
	 * We have to clear the live dedup cache as it might have entries
	 * that are freeable as of now.  Any new entries in the dedup cache
	 * made after this point, even if they become freeable, will have
	 * previously been fully allocated and will be protected by the
	 * 2-stage bulkfree.
	 */
	hammer2_dedup_clear(hmp);

	/*
	 * Setup for free pass using the buffer size specified by the
	 * hammer2 utility, 32K-aligned.
	 */
	bzero(&cbinfo, sizeof(cbinfo));
	size = (bfi->size + HAMMER2_FREEMAP_LEVELN_PSIZE - 1) &
	       ~(size_t)(HAMMER2_FREEMAP_LEVELN_PSIZE - 1);

	/*
	 * Cap at 1/4 physical memory (hammer2 utility will not normally
	 * ever specify a buffer this big, but leave the option available).
	 */
	if (size > kmem_lim_size() * 1024 * 1024 / 4) {
		size = kmem_lim_size() * 1024 * 1024 / 4;
		kprintf("hammer2: Warning: capping bulkfree buffer at %jdM\n",
			(intmax_t)size / (1024 * 1024));
	}

#define HAMMER2_FREEMAP_SIZEDIV	\
	(HAMMER2_FREEMAP_LEVEL1_SIZE / HAMMER2_FREEMAP_LEVELN_PSIZE)

	/*
	 * Cap at the size needed to cover the whole volume to avoid
	 * making an unnecessarily large allocation.
	 */
	if (size > hmp->total_size / HAMMER2_FREEMAP_SIZEDIV)
		size = howmany(hmp->total_size, HAMMER2_FREEMAP_SIZEDIV);

	/*
	 * Minimum bitmap buffer size, then align to a LEVELN_PSIZE (32K)
	 * boundary.
	 */
	if (size < 1024 * 1024)
		size = 1024 * 1024;
	size = (size + HAMMER2_FREEMAP_LEVELN_PSIZE - 1) &
	       ~(size_t)(HAMMER2_FREEMAP_LEVELN_PSIZE - 1);

	cbinfo.hmp = hmp;
	cbinfo.bmap = kmem_alloc_swapbacked(&cbinfo.kp, size, VM_SUBSYS_HAMMER);
	cbinfo.dedup = kmalloc(sizeof(*cbinfo.dedup) * HAMMER2_DEDUP_HEUR_SIZE,
			       M_HAMMER2, M_WAITOK | M_ZERO);

	kprintf("hammer2: bulkfree buf=%jdM\n",
		(intmax_t)size / (1024 * 1024));

	/*
	 * Normalize start point to a 1GB boundary.  We operate on a
	 * 32KB leaf bitmap boundary which represents 1GB of storage.
	 */
	cbinfo.sbase = bfi->sbase;
	if (cbinfo.sbase > hmp->total_size)
		cbinfo.sbase = hmp->total_size;
	cbinfo.sbase &= ~HAMMER2_FREEMAP_LEVEL1_MASK;
	TAILQ_INIT(&cbinfo.list);

	cbinfo.bulkfree_ticks = ticks;

	/*
	 * Loop on a full meta-data scan as many times as required to
	 * get through all available storage.
	 */
	error = 0;
	while (cbinfo.sbase < hmp->total_size) {
		/*
		 * We have enough ram to represent (incr) bytes of storage.
		 * Each 32KB of ram represents 1GB of storage.
		 *
		 * We must also clean out our de-duplication heuristic for
		 * each (incr) bytes of storage, otherwise we wind up not
		 * scanning meta-data for later areas of storage because
		 * they had already been scanned in earlier areas of storage.
		 * Since the ranging is different, we have to restart
		 * the dedup heuristic too.
		 */
		int allmedia;

		cbinfo_bmap_init(&cbinfo, size);
		bzero(cbinfo.dedup, sizeof(*cbinfo.dedup) *
				    HAMMER2_DEDUP_HEUR_SIZE);
		cbinfo.count_inodes_scanned = 0;
		cbinfo.count_dirents_scanned = 0;
		cbinfo.count_bytes_scanned = 0;
		cbinfo.count_chains_scanned = 0;
		cbinfo.count_chains_reported = 0;

		incr = size / HAMMER2_FREEMAP_LEVELN_PSIZE *
		       HAMMER2_FREEMAP_LEVEL1_SIZE;
		if (hmp->total_size - cbinfo.sbase <= incr) {
			cbinfo.sstop = hmp->total_size;
			allmedia = 1;
		} else {
			cbinfo.sstop = cbinfo.sbase + incr;
			allmedia = 0;
		}
		kprintf("hammer2: pass %016jx-%016jx ",
			(intmax_t)cbinfo.sbase,
			(intmax_t)cbinfo.sstop);
		if (allmedia && cbinfo.sbase == 0)
			kprintf("(all media)\n");
		else if (allmedia)
			kprintf("(remaining media)\n");
		else
			kprintf("(%jdGB of media)\n",
				(intmax_t)incr / (1024L*1024*1024));

		/*
		 * Scan topology for stuff inside this range.
		 *
		 * NOTE - By not using a transaction the operation can
		 *	  run concurrent with the frontend as well as
		 *	  with flushes.
		 *
		 *	  We cannot safely set a mtid without a transaction,
		 *	  and in fact we don't want to set one anyway.  We
		 *	  want the bulkfree to be passive and no interfere
		 *	  with crash recovery.
		 */
#undef HAMMER2_BULKFREE_TRANS	/* undef - don't use transaction */
#ifdef HAMMER2_BULKFREE_TRANS
		hammer2_trans_init(hmp->spmp, 0);
		cbinfo.mtid = hammer2_trans_sub(hmp->spmp);
#else
		cbinfo.mtid = 0;
#endif
		cbinfo.pri = 0;
		error |= hammer2_bulkfree_scan(vchain,
					       h2_bulkfree_callback, &cbinfo);

		while ((save = TAILQ_FIRST(&cbinfo.list)) != NULL &&
		       (error & ~HAMMER2_ERROR_CHECK) == 0) {
			TAILQ_REMOVE(&cbinfo.list, save, entry);
			--cbinfo.list_count;
			cbinfo.pri = 0;
			cbinfo.backout = NULL;
			error |= hammer2_bulkfree_scan(save->chain,
						       h2_bulkfree_callback,
						       &cbinfo);
			hammer2_chain_drop(save->chain);
			kfree(save, M_HAMMER2);
		}
		while (save) {
			TAILQ_REMOVE(&cbinfo.list, save, entry);
			--cbinfo.list_count;
			hammer2_chain_drop(save->chain);
			kfree(save, M_HAMMER2);
			save = TAILQ_FIRST(&cbinfo.list);
		}
		cbinfo.backout = NULL;

		/*
		 * If the complete scan succeeded we can synchronize our
		 * in-memory freemap against live storage.  If an abort
		 * occured we cannot safely synchronize our partially
		 * filled-out in-memory freemap.
		 *
		 * We still synchronize on CHECK failures.  That is, we still
		 * want bulkfree to operate even if the filesystem has defects.
		 */
		if (error & ~HAMMER2_ERROR_CHECK) {
			kprintf("bulkfree lastdrop %d %d error=0x%04x\n",
				vchain->refs, vchain->core.chain_count, error);
		} else {
			if (error & HAMMER2_ERROR_CHECK) {
				kprintf("bulkfree lastdrop %d %d "
					"(with check errors)\n",
					vchain->refs, vchain->core.chain_count);
			} else {
				kprintf("bulkfree lastdrop %d %d\n",
					vchain->refs, vchain->core.chain_count);
			}

			error = h2_bulkfree_sync(&cbinfo);

			hammer2_voldata_lock(hmp);
			hammer2_voldata_modify(hmp);
			hmp->voldata.allocator_free += cbinfo.adj_free;
			hammer2_voldata_unlock(hmp);
		}

		/*
		 * Cleanup for next loop.
		 */
#ifdef HAMMER2_BULKFREE_TRANS
		hammer2_trans_done(hmp->spmp, 0);
#endif
		if (error & ~HAMMER2_ERROR_CHECK)
			break;
		cbinfo.sbase = cbinfo.sstop;
		cbinfo.adj_free = 0;
	}
	kmem_free_swapbacked(&cbinfo.kp);
	kfree(cbinfo.dedup, M_HAMMER2);
	cbinfo.dedup = NULL;

	bfi->sstop = cbinfo.sbase;

	incr = bfi->sstop / (hmp->total_size / 10000);
	if (incr > 10000)
		incr = 10000;

	kprintf("bulkfree pass statistics (%d.%02d%% storage processed):\n",
		(int)incr / 100,
		(int)incr % 100);

	if (error & ~HAMMER2_ERROR_CHECK) {
		kprintf("    bulkfree was aborted\n");
	} else {
		if (error & HAMMER2_ERROR_CHECK) {
			kprintf("    WARNING: bulkfree "
				"encountered CRC errors\n");
		}
		kprintf("    transition->free   %ld\n", cbinfo.count_10_00);
		kprintf("    transition->staged %ld\n", cbinfo.count_11_10);
		kprintf("    ERR(00)->allocated %ld\n", cbinfo.count_00_11);
		kprintf("    ERR(01)->allocated %ld\n", cbinfo.count_01_11);
		kprintf("    staged->allocated  %ld\n", cbinfo.count_10_11);
		kprintf("    ~4MB segs cleaned  %ld\n", cbinfo.count_l0cleans);
		kprintf("    linear adjusts     %ld\n",
			cbinfo.count_linadjusts);
		kprintf("    dedup factor       %ld\n",
			cbinfo.count_dedup_factor);
		kprintf("    max saved chains   %ld\n", cbinfo.list_count_max);
	}

	return error;
}

static void
cbinfo_bmap_init(hammer2_bulkfree_info_t *cbinfo, size_t size)
{
	hammer2_bmap_data_t *bmap = cbinfo->bmap;
	hammer2_key_t key = cbinfo->sbase;
	hammer2_key_t lokey;
	hammer2_key_t hikey;

	lokey = (cbinfo->hmp->voldata.allocator_beg + HAMMER2_SEGMASK64) &
		~HAMMER2_SEGMASK64;
	hikey = cbinfo->hmp->total_size & ~HAMMER2_SEGMASK64;

	bzero(bmap, size);
	while (size) {
		bzero(bmap, sizeof(*bmap));
		if (lokey < H2FMBASE(key, HAMMER2_FREEMAP_LEVEL1_RADIX))
			lokey = H2FMBASE(key, HAMMER2_FREEMAP_LEVEL1_RADIX);
		if (lokey < H2FMZONEBASE(key) + HAMMER2_ZONE_SEG64)
			lokey = H2FMZONEBASE(key) + HAMMER2_ZONE_SEG64;
		if (key < lokey || key >= hikey) {
			memset(bmap->bitmapq, -1,
			       sizeof(bmap->bitmapq));
			bmap->avail = 0;
			bmap->linear = HAMMER2_SEGSIZE;
		} else {
			bmap->avail = HAMMER2_FREEMAP_LEVEL0_SIZE;
		}
		size -= sizeof(*bmap);
		key += HAMMER2_FREEMAP_LEVEL0_SIZE;
		++bmap;
	}
}

static int
h2_bulkfree_callback(hammer2_bulkfree_info_t *cbinfo, hammer2_blockref_t *bref)
{
	hammer2_bmap_data_t *bmap;
	hammer2_off_t data_off;
	uint16_t class;
	size_t bytes;
	int radix;

	/*
	 * Check for signal and allow yield to userland during scan.
	 */
	if (hammer2_signal_check(&cbinfo->save_time))
		return HAMMER2_ERROR_ABORTED;

	/*
	 * Deal with kernel thread cpu or I/O hogging by limiting the
	 * number of chains scanned per second to hammer2_bulkfree_tps.
	 * Ignore leaf records (DIRENT and DATA), no per-record I/O is
	 * involved for those since we don't load their data.
	 */
	if (bref->type != HAMMER2_BREF_TYPE_DATA &&
	    bref->type != HAMMER2_BREF_TYPE_DIRENT) {
		++cbinfo->bulkfree_calls;
		if (cbinfo->bulkfree_calls > hammer2_bulkfree_tps) {
			int dticks = ticks - cbinfo->bulkfree_ticks;
			if (dticks < 0)
				dticks = 0;
			if (dticks < hz) {
				tsleep(&cbinfo->bulkfree_ticks, 0,
				       "h2bw", hz - dticks);
			}
			cbinfo->bulkfree_calls = 0;
			cbinfo->bulkfree_ticks = ticks;
		}
	}

	/*
	 * Calculate the data offset and determine if it is within
	 * the current freemap range being gathered.
	 */
	data_off = bref->data_off & ~HAMMER2_OFF_MASK_RADIX;
	if (data_off < cbinfo->sbase || data_off >= cbinfo->sstop)
		return 0;
	if (data_off < cbinfo->hmp->voldata.allocator_beg)
		return 0;
	if (data_off >= cbinfo->hmp->total_size)
		return 0;

	/*
	 * Calculate the information needed to generate the in-memory
	 * freemap record.
	 *
	 * Hammer2 does not allow allocations to cross the L1 (1GB) boundary,
	 * it's a problem if it does.  (Or L0 (4MB) for that matter).
	 */
	radix = (int)(bref->data_off & HAMMER2_OFF_MASK_RADIX);
	KKASSERT(radix != 0);
	bytes = (size_t)1 << radix;
	class = (bref->type << 8) | HAMMER2_PBUFRADIX;

	if (data_off + bytes > cbinfo->sstop) {
		kprintf("hammer2_bulkfree_scan: illegal 1GB boundary "
			"%016jx %016jx/%d\n",
			(intmax_t)bref->data_off,
			(intmax_t)bref->key,
			bref->keybits);
		bytes = cbinfo->sstop - data_off;	/* XXX */
	}

	/*
	 * Convert to a storage offset relative to the beginning of the
	 * storage range we are collecting.  Then lookup the level0 bmap entry.
	 */
	data_off -= cbinfo->sbase;
	bmap = cbinfo->bmap + (data_off >> HAMMER2_FREEMAP_LEVEL0_RADIX);

	/*
	 * Convert data_off to a bmap-relative value (~4MB storage range).
	 * Adjust linear, class, and avail.
	 *
	 * Hammer2 does not allow allocations to cross the L0 (4MB) boundary,
	 */
	data_off &= HAMMER2_FREEMAP_LEVEL0_MASK;
	if (data_off + bytes > HAMMER2_FREEMAP_LEVEL0_SIZE) {
		kprintf("hammer2_bulkfree_scan: illegal 4MB boundary "
			"%016jx %016jx/%d\n",
			(intmax_t)bref->data_off,
			(intmax_t)bref->key,
			bref->keybits);
		bytes = HAMMER2_FREEMAP_LEVEL0_SIZE - data_off;
	}

	if (bmap->class == 0) {
		bmap->class = class;
		bmap->avail = HAMMER2_FREEMAP_LEVEL0_SIZE;
	}

	/*
	 * NOTE: bmap->class does not have to match class.  Classification
	 *	 is relaxed when free space is low, so some mixing can occur.
	 */
#if 0
	/*
	 * XXX removed
	 */
	if (bmap->class != class) {
		kprintf("hammer2_bulkfree_scan: illegal mixed class "
			"%016jx %016jx/%d (%04x vs %04x)\n",
			(intmax_t)bref->data_off,
			(intmax_t)bref->key,
			bref->keybits,
			class, bmap->class);
	}
#endif

	/*
	 * Just record the highest byte-granular offset for now.  Do not
	 * match against allocations which are in multiples of whole blocks.
	 *
	 * Make sure that any in-block linear offset at least covers the
	 * data range.  This can cause bmap->linear to become block-aligned.
	 */
	if (bytes & HAMMER2_FREEMAP_BLOCK_MASK) {
		if (bmap->linear < (int32_t)data_off + (int32_t)bytes)
			bmap->linear = (int32_t)data_off + (int32_t)bytes;
	} else if (bmap->linear >= (int32_t)data_off &&
		   bmap->linear < (int32_t)data_off + (int32_t)bytes) {
		bmap->linear = (int32_t)data_off + (int32_t)bytes;
	}

	/*
	 * Adjust the hammer2_bitmap_t bitmap[HAMMER2_BMAP_ELEMENTS].
	 * 64-bit entries, 2 bits per entry, to code 11.
	 *
	 * NOTE: data_off mask to 524288, shift right by 14 (radix for 16384),
	 *	 and multiply shift amount by 2 for sets of 2 bits.
	 *
	 * NOTE: The allocation can be smaller than HAMMER2_FREEMAP_BLOCK_SIZE.
	 *	 also, data_off may not be FREEMAP_BLOCK_SIZE aligned.
	 */
	while (bytes > 0) {
		hammer2_bitmap_t bmask;
		int bindex;

		bindex = (int)data_off >> (HAMMER2_FREEMAP_BLOCK_RADIX +
					   HAMMER2_BMAP_INDEX_RADIX);
		bmask = (hammer2_bitmap_t)3 <<
			((((int)data_off & HAMMER2_BMAP_INDEX_MASK) >>
			 HAMMER2_FREEMAP_BLOCK_RADIX) << 1);

		/*
		 * NOTE! The (avail) calculation is bitmap-granular.  Multiple
		 *	 sub-granular records can wind up at the same bitmap
		 *	 position.
		 */
		if ((bmap->bitmapq[bindex] & bmask) == 0) {
			if (bytes < HAMMER2_FREEMAP_BLOCK_SIZE) {
				bmap->avail -= HAMMER2_FREEMAP_BLOCK_SIZE;
			} else {
				bmap->avail -= bytes;
			}
			bmap->bitmapq[bindex] |= bmask;
		}
		data_off += HAMMER2_FREEMAP_BLOCK_SIZE;
		if (bytes < HAMMER2_FREEMAP_BLOCK_SIZE)
			bytes = 0;
		else
			bytes -= HAMMER2_FREEMAP_BLOCK_SIZE;
	}
	return 0;
}

/*
 * Synchronize the in-memory bitmap with the live freemap.  This is not a
 * direct copy.  Instead the bitmaps must be compared:
 *
 *	In-memory	Live-freemap
 *	   00		  11 -> 10	(do nothing if live modified)
 *			  10 -> 00	(do nothing if live modified)
 *	   11		  10 -> 11	handles race against live
 *			  ** -> 11	nominally warn of corruption
 *
 * We must also fixup the hints in HAMMER2_BREF_TYPE_FREEMAP_LEAF.
 */
static int
h2_bulkfree_sync(hammer2_bulkfree_info_t *cbinfo)
{
	hammer2_off_t data_off;
	hammer2_key_t key;
	hammer2_key_t key_dummy;
	hammer2_bmap_data_t *bmap;
	hammer2_bmap_data_t *live;
	hammer2_chain_t *live_parent;
	hammer2_chain_t *live_chain;
	int bmapindex;
	int error;

	kprintf("hammer2_bulkfree - range ");

	if (cbinfo->sbase < cbinfo->hmp->voldata.allocator_beg)
		kprintf("%016jx-",
			(intmax_t)cbinfo->hmp->voldata.allocator_beg);
	else
		kprintf("%016jx-",
			(intmax_t)cbinfo->sbase);

	if (cbinfo->sstop > cbinfo->hmp->total_size)
		kprintf("%016jx\n",
			(intmax_t)cbinfo->hmp->total_size);
	else
		kprintf("%016jx\n",
			(intmax_t)cbinfo->sstop);

	data_off = cbinfo->sbase;
	bmap = cbinfo->bmap;

	live_parent = &cbinfo->hmp->fchain;
	hammer2_chain_ref(live_parent);
	hammer2_chain_lock(live_parent, HAMMER2_RESOLVE_ALWAYS);
	live_chain = NULL;
	error = 0;

	/*
	 * Iterate each hammer2_bmap_data_t line (128 bytes) managing
	 * 4MB of storage.
	 */
	while (data_off < cbinfo->sstop) {
		/*
		 * The freemap is not used below allocator_beg or beyond
		 * total_size.
		 */

		if (data_off < cbinfo->hmp->voldata.allocator_beg)
			goto next;
		if (data_off >= cbinfo->hmp->total_size)
			goto next;

		/*
		 * Locate the freemap leaf on the live filesystem
		 */
		key = (data_off & ~HAMMER2_FREEMAP_LEVEL1_MASK);

		if (live_chain == NULL || live_chain->bref.key != key) {
			if (live_chain) {
				hammer2_chain_unlock(live_chain);
				hammer2_chain_drop(live_chain);
			}
			live_chain = hammer2_chain_lookup(
					    &live_parent,
					    &key_dummy,
					    key,
					    key + HAMMER2_FREEMAP_LEVEL1_MASK,
					    &error,
					    HAMMER2_LOOKUP_ALWAYS);
			if (error) {
				kprintf("hammer2_bulkfree: freemap lookup "
					"error near %016jx, error %s\n",
					(intmax_t)data_off,
					hammer2_error_str(live_chain->error));
				break;
			}
		}
		if (live_chain == NULL) {
			/*
			 * XXX if we implement a full recovery mode we need
			 * to create/recreate missing freemap chains if our
			 * bmap has any allocated blocks.
			 */
			if (bmap->class &&
			    bmap->avail != HAMMER2_FREEMAP_LEVEL0_SIZE) {
				kprintf("hammer2_bulkfree: cannot locate "
					"live leaf for allocated data "
					"near %016jx\n",
					(intmax_t)data_off);
			}
			goto next;
		}
		if (live_chain->error) {
			kprintf("hammer2_bulkfree: unable to access freemap "
				"near %016jx, error %s\n",
				(intmax_t)data_off,
				hammer2_error_str(live_chain->error));
			hammer2_chain_unlock(live_chain);
			hammer2_chain_drop(live_chain);
			live_chain = NULL;
			goto next;
		}

		bmapindex = (data_off & HAMMER2_FREEMAP_LEVEL1_MASK) >>
			    HAMMER2_FREEMAP_LEVEL0_RADIX;
		live = &live_chain->data->bmdata[bmapindex];

		/*
		 * Shortcut if the bitmaps match and the live linear
		 * indicator is sane.  We can't do a perfect check of
		 * live->linear because the only real requirement is that
		 * if it is not block-aligned, that it not cover the space
		 * within its current block which overlaps one of the data
		 * ranges we scan.  We don't retain enough fine-grained
		 * data in our scan to be able to set it exactly.
		 *
		 * TODO - we could shortcut this by testing that both
		 * live->class and bmap->class are 0, and both avails are
		 * set to HAMMER2_FREEMAP_LEVEL0_SIZE (4MB).
		 */
		if (bcmp(live->bitmapq, bmap->bitmapq,
			 sizeof(bmap->bitmapq)) == 0 &&
		    live->linear >= bmap->linear &&
		    (hammer2_aux_flags & 1) == 0 &&
		    bigmask_good(bmap, live_chain->bref.check.freemap.bigmask))
		{
			goto next;
		}
		if (hammer2_debug & 1) {
			kprintf("live %016jx %04d.%04x (avail=%d) "
				"bigmask %08x->%08x\n",
				data_off, bmapindex, live->class, live->avail,
				live_chain->bref.check.freemap.bigmask,
				live_chain->bref.check.freemap.bigmask |
				bigmask_get(bmap));
		}

		if (hammer2_chain_modify(live_chain, cbinfo->mtid, 0, 0)) {
			kprintf("hammer2_bulkfree: unable to modify freemap "
				"at %016jx for data-block %016jx, error %s\n",
				live_chain->bref.data_off,
				(intmax_t)data_off,
				hammer2_error_str(live_chain->error));
			hammer2_chain_unlock(live_chain);
			hammer2_chain_drop(live_chain);
			live_chain = NULL;
			goto next;
		}
		live_chain->bref.check.freemap.bigmask = -1;
		cbinfo->hmp->freemap_relaxed = 0;	/* reset heuristic */
		live = &live_chain->data->bmdata[bmapindex];

		h2_bulkfree_sync_adjust(cbinfo, data_off, live, bmap,
					live_chain->bref.key +
					bmapindex *
					HAMMER2_FREEMAP_LEVEL0_SIZE);
next:
		data_off += HAMMER2_FREEMAP_LEVEL0_SIZE;
		++bmap;
	}
	if (live_chain) {
		hammer2_chain_unlock(live_chain);
		hammer2_chain_drop(live_chain);
	}
	if (live_parent) {
		hammer2_chain_unlock(live_parent);
		hammer2_chain_drop(live_parent);
	}
	return error;
}

/*
 * Merge the bulkfree bitmap against the existing bitmap.
 */
static
void
h2_bulkfree_sync_adjust(hammer2_bulkfree_info_t *cbinfo,
			hammer2_off_t data_off, hammer2_bmap_data_t *live,
			hammer2_bmap_data_t *bmap, hammer2_key_t alloc_base)
{
	int bindex;
	int scount;
	hammer2_off_t tmp_off;
	hammer2_bitmap_t lmask;
	hammer2_bitmap_t mmask;

	tmp_off = data_off;

	for (bindex = 0; bindex < HAMMER2_BMAP_ELEMENTS; ++bindex) {
		lmask = live->bitmapq[bindex];	/* live */
		mmask = bmap->bitmapq[bindex];	/* snapshotted bulkfree */
		if (lmask == mmask) {
			tmp_off += HAMMER2_BMAP_INDEX_SIZE;
			continue;
		}

		for (scount = 0;
		     scount < HAMMER2_BMAP_BITS_PER_ELEMENT;
		     scount += 2) {
			if ((mmask & 3) == 0) {
				/*
				 * in-memory 00		live 11 -> 10
				 *			live 10 -> 00
				 *
				 * Storage might be marked allocated or
				 * staged and must be remarked staged or
				 * free.
				 */
				switch (lmask & 3) {
				case 0:	/* 00 */
					break;
				case 1:	/* 01 */
					kprintf("hammer2_bulkfree: cannot "
						"transition m=00/l=01\n");
					break;
				case 2:	/* 10 -> 00 */
					live->bitmapq[bindex] &=
					    ~((hammer2_bitmap_t)2 << scount);
					live->avail +=
						HAMMER2_FREEMAP_BLOCK_SIZE;
					if (live->avail >
					    HAMMER2_FREEMAP_LEVEL0_SIZE) {
						live->avail =
						    HAMMER2_FREEMAP_LEVEL0_SIZE;
					}
					cbinfo->adj_free +=
						HAMMER2_FREEMAP_BLOCK_SIZE;
					++cbinfo->count_10_00;
					hammer2_io_dedup_assert(
						cbinfo->hmp,
						tmp_off |
						HAMMER2_FREEMAP_BLOCK_RADIX,
						HAMMER2_FREEMAP_BLOCK_SIZE);
					break;
				case 3:	/* 11 -> 10 */
					live->bitmapq[bindex] &=
					    ~((hammer2_bitmap_t)1 << scount);
					++cbinfo->count_11_10;
					hammer2_io_dedup_delete(
						cbinfo->hmp,
						HAMMER2_BREF_TYPE_DATA,
						tmp_off |
						HAMMER2_FREEMAP_BLOCK_RADIX,
						HAMMER2_FREEMAP_BLOCK_SIZE);
					break;
				}
			} else if ((mmask & 3) == 3) {
				/*
				 * in-memory 11		live 10 -> 11
				 *			live ** -> 11
				 *
				 * Storage might be incorrectly marked free
				 * or staged and must be remarked fully
				 * allocated.
				 */
				switch (lmask & 3) {
				case 0:	/* 00 */
					/*
					 * This case is not supposed to
					 * happen.  If it does, it means
					 * that an allocated block was
					 * thought by the filesystem to be
					 * free.
					 */
					kprintf("hammer2_bulkfree: "
						"00->11 critical freemap "
						"transition for datablock "
						"%016jx\n",
						tmp_off);
					++cbinfo->count_00_11;
					cbinfo->adj_free -=
						HAMMER2_FREEMAP_BLOCK_SIZE;
					live->avail -=
						HAMMER2_FREEMAP_BLOCK_SIZE;
					if ((int32_t)live->avail < 0)
						live->avail = 0;
					break;
				case 1:	/* 01 */
					++cbinfo->count_01_11;
					break;
				case 2:	/* 10 -> 11 */
					++cbinfo->count_10_11;
					break;
				case 3:	/* 11 */
					break;
				}
				live->bitmapq[bindex] |=
					((hammer2_bitmap_t)3 << scount);
			}
			mmask >>= 2;
			lmask >>= 2;
			tmp_off += HAMMER2_FREEMAP_BLOCK_SIZE;
		}
	}

	/*
	 * Determine if the live bitmap is completely free and reset its
	 * fields if so.  Otherwise check to see if we can reduce the linear
	 * offset.
	 */
	for (bindex = HAMMER2_BMAP_ELEMENTS - 1; bindex >= 0; --bindex) {
		if (live->bitmapq[bindex] != 0)
			break;
	}
	if (bindex < 0) {
		/*
		 * Completely empty, reset entire segment
		 */
#if 0
		kprintf("hammer2: cleanseg %016jx.%04x (%d)\n",
			alloc_base, live->class, live->avail);
#endif
		live->avail = HAMMER2_FREEMAP_LEVEL0_SIZE;
		live->class = 0;
		live->linear = 0;
		++cbinfo->count_l0cleans;
	} else if (bindex < 7) {
		/*
		 * Partially full, bitmapq[bindex] != 0.  Our bulkfree pass
		 * does not record enough information to set live->linear
		 * exactly.
		 *
		 * NOTE: Setting live->linear to a sub-block (16K) boundary
		 *	 forces the live code to iterate to the next fully
		 *	 free block.  It does NOT mean that all blocks above
		 *	 live->linear are available.
		 *
		 *	 Setting live->linear to a fragmentary (less than
		 *	 16K) boundary allows allocations to iterate within
		 *	 that sub-block.
		 */
		if (live->linear < bmap->linear &&
		    ((live->linear ^ bmap->linear) &
		     ~HAMMER2_FREEMAP_BLOCK_MASK) == 0) {
			/*
			 * If greater than but still within the same
			 * sub-block as live we can adjust linear upward.
			 */
			live->linear = bmap->linear;
			++cbinfo->count_linadjusts;
		} else {
			/*
			 * Otherwise adjust to the nearest higher or same
			 * sub-block boundary.  The live system may have
			 * bounced live->linear around so we cannot make any
			 * assumptions with regards to available fragmentary
			 * allocations.
			 */
			live->linear =
				(bmap->linear + HAMMER2_FREEMAP_BLOCK_MASK) &
				~HAMMER2_FREEMAP_BLOCK_MASK;
			++cbinfo->count_linadjusts;
		}
	} else {
		/*
		 * Completely full, effectively disable the linear iterator
		 */
		live->linear = HAMMER2_SEGSIZE;
	}

#if 0
	if (bmap->class) {
		kprintf("%016jx %04d.%04x (avail=%7d) "
			"%08x %08x %08x %08x %08x %08x %08x %08x\n",
			(intmax_t)data_off,
			(int)((data_off &
			       HAMMER2_FREEMAP_LEVEL1_MASK) >>
			      HAMMER2_FREEMAP_LEVEL0_RADIX),
			bmap->class,
			bmap->avail,
			bmap->bitmap[0], bmap->bitmap[1],
			bmap->bitmap[2], bmap->bitmap[3],
			bmap->bitmap[4], bmap->bitmap[5],
			bmap->bitmap[6], bmap->bitmap[7]);
	}
#endif
}

/*
 * BULKFREE DEDUP HEURISTIC
 *
 * WARNING! This code is SMP safe but the heuristic allows SMP collisions.
 *	    All fields must be loaded into locals and validated.
 */
static
int
h2_bulkfree_test(hammer2_bulkfree_info_t *cbinfo, hammer2_blockref_t *bref,
		 int pri, int saved_error)
{
	hammer2_dedup_t *dedup;
	int best;
	int n;
	int i;

	n = hammer2_icrc32(&bref->data_off, sizeof(bref->data_off));
	dedup = cbinfo->dedup + (n & (HAMMER2_DEDUP_HEUR_MASK & ~7));

	for (i = best = 0; i < 8; ++i) {
		if (dedup[i].data_off == bref->data_off) {
			if (dedup[i].ticks < pri)
				dedup[i].ticks = pri;
			if (pri == 1)
				cbinfo->count_dedup_factor += dedup[i].ticks;
			return (dedup[i].saved_error | HAMMER2_ERROR_EOF);
		}
		if (dedup[i].ticks < dedup[best].ticks)
			best = i;
	}
	dedup[best].data_off = bref->data_off;
	dedup[best].ticks = pri;
	dedup[best].saved_error = saved_error;

	return 0;
}

/*
 * Calculate what the bigmask should be.  bigmask is permissive, so the
 * bits returned must be set at a minimum in the live bigmask.  Other bits
 * might also be set in the live bigmask.
 */
static uint32_t
bigmask_get(hammer2_bmap_data_t *bmap)
{
	hammer2_bitmap_t mask;	/* 64-bit mask to check */
	hammer2_bitmap_t scan;
	uint32_t bigmask;
	uint32_t radix_mask;
	int iter;
	int i;
	int j;

	bigmask = 0;
	for (i = 0; i < HAMMER2_BMAP_ELEMENTS; ++i) {
		mask = bmap->bitmapq[i];

		radix_mask = 1U << HAMMER2_FREEMAP_BLOCK_RADIX;
		radix_mask |= radix_mask - 1;
		iter = 2;	/* each bitmap entry is 2 bits. 2, 4, 8... */
		while (iter <= HAMMER2_BMAP_BITS_PER_ELEMENT) {
			if (iter == HAMMER2_BMAP_BITS_PER_ELEMENT)
				scan = -1;
			else
				scan = (1LU << iter) - 1;
			j = 0;
			while (j < HAMMER2_BMAP_BITS_PER_ELEMENT) {
				/*
				 * Check if all bits are 0 (free block).
				 * If so, set the bit in bigmask for the
				 * allocation radix under test.
				 */
				if ((scan & mask) == 0) {
					bigmask |= radix_mask;
				}
				scan <<= iter;
				j += iter;
			}
			iter <<= 1;
			radix_mask = (radix_mask << 1) | 1;
		}
	}
	return bigmask;
}

static int
bigmask_good(hammer2_bmap_data_t *bmap, uint32_t live_bigmask)
{
	uint32_t bigmask;

	bigmask = bigmask_get(bmap);
	return ((live_bigmask & bigmask) == bigmask);
}