[dragonfly.git] / sys / vfs / hammer / hammer_undo.c

/*
 * Copyright (c) 2008 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.
 * 
 * $DragonFly: src/sys/vfs/hammer/hammer_undo.c,v 1.20 2008/07/18 00:19:53 dillon Exp $
 */

/*
 * HAMMER undo - undo buffer/FIFO management.
 */

#include "hammer.h"

static int hammer_und_rb_compare(hammer_undo_t node1, hammer_undo_t node2);

RB_GENERATE2(hammer_und_rb_tree, hammer_undo, rb_node,
             hammer_und_rb_compare, hammer_off_t, offset);

/*
 * Convert a zone-3 undo offset into a zone-2 buffer offset.
 */
hammer_off_t
hammer_undo_lookup(hammer_mount_t hmp, hammer_off_t zone3_off, int *errorp)
{
	hammer_volume_t root_volume;
	hammer_blockmap_t undomap;
	hammer_off_t result_offset;
	int i;

	KKASSERT((zone3_off & HAMMER_OFF_ZONE_MASK) == HAMMER_ZONE_UNDO);
	root_volume = hammer_get_root_volume(hmp, errorp);
	if (*errorp)
		return(0);
	undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
	KKASSERT(HAMMER_ZONE_DECODE(undomap->alloc_offset) == HAMMER_ZONE_UNDO_INDEX);
	KKASSERT (zone3_off < undomap->alloc_offset);

	i = (zone3_off & HAMMER_OFF_SHORT_MASK) / HAMMER_LARGEBLOCK_SIZE;
	result_offset = root_volume->ondisk->vol0_undo_array[i] +
			(zone3_off & HAMMER_LARGEBLOCK_MASK64);

	hammer_rel_volume(root_volume, 0);
	return(result_offset);
}

/*
 * Generate an UNDO record for the block of data at the specified zone1
 * or zone2 offset.
 *
 * The recovery code will execute UNDOs in reverse order, allowing overlaps.
 * All the UNDOs are executed together so if we already laid one down we
 * do not have to lay another one down for the same range.
 */
int
hammer_generate_undo(hammer_transaction_t trans, hammer_io_t io,
		     hammer_off_t zone_off, void *base, int len)
{
	hammer_mount_t hmp;
	hammer_volume_t root_volume;
	hammer_blockmap_t undomap;
	hammer_buffer_t buffer = NULL;
	hammer_fifo_undo_t undo;
	hammer_fifo_tail_t tail;
	hammer_off_t next_offset;
	int error;
	int bytes;

	hmp = trans->hmp;

	/*
	 * Enter the offset into our undo history.  If there is an existing
	 * undo we do not have to generate a new one.
	 */
	if (hammer_enter_undo_history(hmp, zone_off, len) == EALREADY)
		return(0);

	root_volume = trans->rootvol;
	undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];

	/* no undo recursion */
	hammer_modify_volume(NULL, root_volume, NULL, 0);

	hammer_lock_ex(&hmp->undo_lock);
again:
	/*
	 * Allocate space in the FIFO
	 */
	bytes = ((len + HAMMER_HEAD_ALIGN_MASK) & ~HAMMER_HEAD_ALIGN_MASK) +
		sizeof(struct hammer_fifo_undo) +
		sizeof(struct hammer_fifo_tail);
	if (hammer_undo_space(trans) < bytes + HAMMER_BUFSIZE*2)
		panic("hammer: insufficient undo FIFO space!");

	next_offset = undomap->next_offset;

	/*
	 * Wrap next_offset
	 */
	if (undomap->next_offset == undomap->alloc_offset) {
		next_offset = HAMMER_ZONE_ENCODE(HAMMER_ZONE_UNDO_INDEX, 0);
		undomap->next_offset = next_offset;
	}

	/*
	 * This is a tail-chasing FIFO, when we hit the start of a new
	 * buffer we don't have to read it in.
	 */
	if ((next_offset & HAMMER_BUFMASK) == 0)
		undo = hammer_bnew(hmp, next_offset, &error, &buffer);
	else
		undo = hammer_bread(hmp, next_offset, &error, &buffer);
	if (error)
		goto done;

	hammer_modify_buffer(NULL, buffer, NULL, 0);

	KKASSERT(undomap->next_offset == next_offset);

	/*
	 * The FIFO entry would cross a buffer boundary, PAD to the end
	 * of the buffer and try again.  Due to our data alignment, the
	 * worst case (smallest) PAD record is 8 bytes.  PAD records only
	 * populate the first 8 bytes of hammer_fifo_head and the tail may
	 * be at the same offset as the head.
	 */
	if ((next_offset ^ (next_offset + bytes)) & ~HAMMER_BUFMASK64) {
		bytes = HAMMER_BUFSIZE - ((int)next_offset & HAMMER_BUFMASK);
		tail = (void *)((char *)undo + bytes - sizeof(*tail));
		if ((void *)undo != (void *)tail) {
			tail->tail_signature = HAMMER_TAIL_SIGNATURE;
			tail->tail_type = HAMMER_HEAD_TYPE_PAD;
			tail->tail_size = bytes;
		}
		undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
		undo->head.hdr_type = HAMMER_HEAD_TYPE_PAD;
		undo->head.hdr_size = bytes;
		/* NO CRC */
		undomap->next_offset += bytes;
		hammer_modify_buffer_done(buffer);
		goto again;
	}
	if (hammer_debug_general & 0x0080) {
		kprintf("undo %016llx %d %d\n",
			(long long)next_offset, bytes, len);
	}

	/*
	 * We're good, create the entry.
	 */
	undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
	undo->head.hdr_type = HAMMER_HEAD_TYPE_UNDO;
	undo->head.hdr_size = bytes;
	undo->head.reserved01 = 0;
	undo->head.hdr_crc = 0;
	undo->undo_offset = zone_off;
	undo->undo_data_bytes = len;
	bcopy(base, undo + 1, len);

	tail = (void *)((char *)undo + bytes - sizeof(*tail));
	tail->tail_signature = HAMMER_TAIL_SIGNATURE;
	tail->tail_type = HAMMER_HEAD_TYPE_UNDO;
	tail->tail_size = bytes;

	KKASSERT(bytes >= sizeof(undo->head));
	undo->head.hdr_crc = crc32(undo, HAMMER_FIFO_HEAD_CRCOFF) ^
			     crc32(&undo->head + 1, bytes - sizeof(undo->head));
	undomap->next_offset += bytes;

	hammer_modify_buffer_done(buffer);
done:
	hammer_modify_volume_done(root_volume);
	hammer_unlock(&hmp->undo_lock);

	if (buffer)
		hammer_rel_buffer(buffer, 0);
	return(error);
}

/*
 * UNDO HISTORY API
 *
 * It is not necessary to layout an undo record for the same address space
 * multiple times.  Maintain a cache of recent undo's.
 */

/*
 * Enter an undo into the history.  Return EALREADY if the request completely
 * covers a previous request.
 */
int
hammer_enter_undo_history(hammer_mount_t hmp, hammer_off_t offset, int bytes)
{
	hammer_undo_t node;
	hammer_undo_t onode;

	node = RB_LOOKUP(hammer_und_rb_tree, &hmp->rb_undo_root, offset);
	if (node) {
		TAILQ_REMOVE(&hmp->undo_lru_list, node, lru_entry);
		TAILQ_INSERT_TAIL(&hmp->undo_lru_list, node, lru_entry);
		if (bytes <= node->bytes)
			return(EALREADY);
		node->bytes = bytes;
		return(0);
	}
	if (hmp->undo_alloc != HAMMER_MAX_UNDOS) {
		node = &hmp->undos[hmp->undo_alloc++];
	} else {
		node = TAILQ_FIRST(&hmp->undo_lru_list);
		TAILQ_REMOVE(&hmp->undo_lru_list, node, lru_entry);
		RB_REMOVE(hammer_und_rb_tree, &hmp->rb_undo_root, node);
	}
	node->offset = offset;
	node->bytes = bytes;
	TAILQ_INSERT_TAIL(&hmp->undo_lru_list, node, lru_entry);
	onode = RB_INSERT(hammer_und_rb_tree, &hmp->rb_undo_root, node);
	KKASSERT(onode == NULL);
	return(0);
}

void
hammer_clear_undo_history(hammer_mount_t hmp)
{
	RB_INIT(&hmp->rb_undo_root);
	TAILQ_INIT(&hmp->undo_lru_list);
	hmp->undo_alloc = 0;
}

/*
 * Return how much of the undo FIFO has been used
 *
 * The calculation includes undo FIFO space still reserved from a previous
 * flush (because it will still be run on recovery if a crash occurs and
 * we can't overwrite it yet).
 */
int64_t
hammer_undo_used(hammer_transaction_t trans)
{
	hammer_blockmap_t cundomap;
	hammer_blockmap_t dundomap;
	int64_t max_bytes;
	int64_t bytes;

	cundomap = &trans->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
	dundomap = &trans->rootvol->ondisk->
				vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];

	if (dundomap->first_offset <= cundomap->next_offset) {
		bytes = cundomap->next_offset - dundomap->first_offset;
	} else {
		bytes = cundomap->alloc_offset - dundomap->first_offset +
		        (cundomap->next_offset & HAMMER_OFF_LONG_MASK);
	}
	max_bytes = cundomap->alloc_offset & HAMMER_OFF_SHORT_MASK;
	KKASSERT(bytes <= max_bytes);
	return(bytes);
}

/*
 * Return how much of the undo FIFO is available for new records.
 */
int64_t
hammer_undo_space(hammer_transaction_t trans)
{
	hammer_blockmap_t rootmap;
	int64_t max_bytes;

	rootmap = &trans->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
	max_bytes = rootmap->alloc_offset & HAMMER_OFF_SHORT_MASK;
	return(max_bytes - hammer_undo_used(trans));
}

int64_t
hammer_undo_max(hammer_mount_t hmp)
{
	hammer_blockmap_t rootmap;
	int64_t max_bytes;

	rootmap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
	max_bytes = rootmap->alloc_offset & HAMMER_OFF_SHORT_MASK;

	return(max_bytes);
}

static int
hammer_und_rb_compare(hammer_undo_t node1, hammer_undo_t node2)
{
        if (node1->offset < node2->offset)
                return(-1);
        if (node1->offset > node2->offset)
                return(1);
        return(0);
}
Commit	Line	Data
bf686dbe MD	1	/*
	2	* Copyright (c) 2008 The DragonFly Project. All rights reserved.
	3	*
	4	* This code is derived from software contributed to The DragonFly Project
	5	* by Matthew Dillon <dillon@backplane.com>
	6	*
	7	* Redistribution and use in source and binary forms, with or without
	8	* modification, are permitted provided that the following conditions
	9	* are met:
	10	*
	11	* 1. Redistributions of source code must retain the above copyright
	12	* notice, this list of conditions and the following disclaimer.
	13	* 2. Redistributions in binary form must reproduce the above copyright
	14	* notice, this list of conditions and the following disclaimer in
	15	* the documentation and/or other materials provided with the
	16	* distribution.
	17	* 3. Neither the name of The DragonFly Project nor the names of its
	18	* contributors may be used to endorse or promote products derived
	19	* from this software without specific, prior written permission.
	20	*
	21	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	22	* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	23	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
	24	* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
	25	* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
	26	* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
	27	* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	28	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
	29	* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	30	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
	31	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	* SUCH DAMAGE.
	33	*
cdb6e4e6	34	* $DragonFly: src/sys/vfs/hammer/hammer_undo.c,v 1.20 2008/07/18 00:19:53 dillon Exp $
bf686dbe MD	35	*/
	36
	37	/*
	38	* HAMMER undo - undo buffer/FIFO management.
	39	*/
	40
	41	#include "hammer.h"
	42
e8599db1 MD	43	static int hammer_und_rb_compare(hammer_undo_t node1, hammer_undo_t node2);
	44
	45	RB_GENERATE2(hammer_und_rb_tree, hammer_undo, rb_node,
	46	hammer_und_rb_compare, hammer_off_t, offset);
	47
bf686dbe MD	48	/*
	49	* Convert a zone-3 undo offset into a zone-2 buffer offset.
	50	*/
	51	hammer_off_t
	52	hammer_undo_lookup(hammer_mount_t hmp, hammer_off_t zone3_off, int *errorp)
	53	{
	54	hammer_volume_t root_volume;
	55	hammer_blockmap_t undomap;
bf686dbe MD	56	hammer_off_t result_offset;
	57	int i;
	58
	59	KKASSERT((zone3_off & HAMMER_OFF_ZONE_MASK) == HAMMER_ZONE_UNDO);
	60	root_volume = hammer_get_root_volume(hmp, errorp);
	61	if (*errorp)
	62	return(0);
0729c8c8	63	undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
bf686dbe MD	64	KKASSERT(HAMMER_ZONE_DECODE(undomap->alloc_offset) == HAMMER_ZONE_UNDO_INDEX);
	65	KKASSERT (zone3_off < undomap->alloc_offset);
	66
	67	i = (zone3_off & HAMMER_OFF_SHORT_MASK) / HAMMER_LARGEBLOCK_SIZE;
cb51be26	68	result_offset = root_volume->ondisk->vol0_undo_array[i] +
bf686dbe MD	69	(zone3_off & HAMMER_LARGEBLOCK_MASK64);
	70
	71	hammer_rel_volume(root_volume, 0);
	72	return(result_offset);
	73	}
	74
	75	/*
	76	* Generate an UNDO record for the block of data at the specified zone1
f90dde4c	77	* or zone2 offset.
e8599db1 MD	78	*
	79	* The recovery code will execute UNDOs in reverse order, allowing overlaps.
	80	* All the UNDOs are executed together so if we already laid one down we
	81	* do not have to lay another one down for the same range.
bf686dbe MD	82	*/
bf686dbe MD	83	int
059819e3	84	hammer_generate_undo(hammer_transaction_t trans, hammer_io_t io,
f90dde4c	85	hammer_off_t zone_off, void *base, int len)
bf686dbe	86	{
d99d6bf5	87	hammer_mount_t hmp;
bf686dbe	88	hammer_volume_t root_volume;
bf686dbe MD	89	hammer_blockmap_t undomap;
bf686dbe MD	90	hammer_buffer_t buffer = NULL;
bf686dbe MD	91	hammer_fifo_undo_t undo;
	92	hammer_fifo_tail_t tail;
	93	hammer_off_t next_offset;
bf686dbe MD	94	int error;
	95	int bytes;
	96
d99d6bf5 MD	97	hmp = trans->hmp;
d99d6bf5 MD	98
e8599db1 MD	99	/*
	100	* Enter the offset into our undo history. If there is an existing
	101	* undo we do not have to generate a new one.
	102	*/
d99d6bf5	103	if (hammer_enter_undo_history(hmp, zone_off, len) == EALREADY)
e8599db1	104	return(0);
e8599db1	105
b58c6388	106	root_volume = trans->rootvol;
d99d6bf5	107	undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
36f82b23 MD	108
	109	/* no undo recursion */
	110	hammer_modify_volume(NULL, root_volume, NULL, 0);
bf686dbe	111
d99d6bf5	112	hammer_lock_ex(&hmp->undo_lock);
f90dde4c	113	again:
bf686dbe MD	114	/*
	115	* Allocate space in the FIFO
	116	*/
f90dde4c MD	117	bytes = ((len + HAMMER_HEAD_ALIGN_MASK) & ~HAMMER_HEAD_ALIGN_MASK) +
	118	sizeof(struct hammer_fifo_undo) +
	119	sizeof(struct hammer_fifo_tail);
06ad81ff	120	if (hammer_undo_space(trans) < bytes + HAMMER_BUFSIZE*2)
1f07f686	121	panic("hammer: insufficient undo FIFO space!");
f90dde4c	122
bf686dbe MD	123	next_offset = undomap->next_offset;
	124
	125	/*
	126	* Wrap next_offset
	127	*/
	128	if (undomap->next_offset == undomap->alloc_offset) {
	129	next_offset = HAMMER_ZONE_ENCODE(HAMMER_ZONE_UNDO_INDEX, 0);
	130	undomap->next_offset = next_offset;
bf686dbe MD	131	}
bf686dbe MD	132
bf686dbe	133	/*
d99d6bf5 MD	134	* This is a tail-chasing FIFO, when we hit the start of a new
d99d6bf5 MD	135	* buffer we don't have to read it in.
bf686dbe	136	*/
d99d6bf5 MD	137	if ((next_offset & HAMMER_BUFMASK) == 0)
	138	undo = hammer_bnew(hmp, next_offset, &error, &buffer);
	139	else
	140	undo = hammer_bread(hmp, next_offset, &error, &buffer);
cdb6e4e6 MD	141	if (error)
	142	goto done;
	143
d99d6bf5 MD	144	hammer_modify_buffer(NULL, buffer, NULL, 0);
	145
	146	KKASSERT(undomap->next_offset == next_offset);
c9b9e29d	147
bf686dbe MD	148	/*
	149	* The FIFO entry would cross a buffer boundary, PAD to the end
	150	* of the buffer and try again. Due to our data alignment, the
	151	* worst case (smallest) PAD record is 8 bytes. PAD records only
	152	* populate the first 8 bytes of hammer_fifo_head and the tail may
	153	* be at the same offset as the head.
	154	*/
c9b9e29d	155	if ((next_offset ^ (next_offset + bytes)) & ~HAMMER_BUFMASK64) {
bf686dbe MD	156	bytes = HAMMER_BUFSIZE - ((int)next_offset & HAMMER_BUFMASK);
	157	tail = (void )((char )undo + bytes - sizeof(*tail));
	158	if ((void )undo != (void )tail) {
	159	tail->tail_signature = HAMMER_TAIL_SIGNATURE;
	160	tail->tail_type = HAMMER_HEAD_TYPE_PAD;
	161	tail->tail_size = bytes;
	162	}
	163	undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
	164	undo->head.hdr_type = HAMMER_HEAD_TYPE_PAD;
	165	undo->head.hdr_size = bytes;
19619882	166	/* NO CRC */
bf686dbe	167	undomap->next_offset += bytes;
10a5d1ba	168	hammer_modify_buffer_done(buffer);
bf686dbe MD	169	goto again;
bf686dbe MD	170	}
973c11b9 MD	171	if (hammer_debug_general & 0x0080) {
	172	kprintf("undo %016llx %d %d\n",
	173	(long long)next_offset, bytes, len);
	174	}
bf686dbe MD	175
	176	/*
	177	* We're good, create the entry.
	178	*/
	179	undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
f90dde4c	180	undo->head.hdr_type = HAMMER_HEAD_TYPE_UNDO;
bf686dbe	181	undo->head.hdr_size = bytes;
059819e3 MD	182	undo->head.reserved01 = 0;
059819e3 MD	183	undo->head.hdr_crc = 0;
f90dde4c	184	undo->undo_offset = zone_off;
bf686dbe MD	185	undo->undo_data_bytes = len;
bf686dbe MD	186	bcopy(base, undo + 1, len);
f90dde4c MD	187
	188	tail = (void )((char )undo + bytes - sizeof(*tail));
	189	tail->tail_signature = HAMMER_TAIL_SIGNATURE;
	190	tail->tail_type = HAMMER_HEAD_TYPE_UNDO;
	191	tail->tail_size = bytes;
	192
19619882 MD	193	KKASSERT(bytes >= sizeof(undo->head));
	194	undo->head.hdr_crc = crc32(undo, HAMMER_FIFO_HEAD_CRCOFF) ^
	195	crc32(&undo->head + 1, bytes - sizeof(undo->head));
bf686dbe	196	undomap->next_offset += bytes;
c9b9e29d MD	197
c9b9e29d MD	198	hammer_modify_buffer_done(buffer);
cdb6e4e6	199	done:
10a5d1ba	200	hammer_modify_volume_done(root_volume);
d99d6bf5 MD	201	hammer_unlock(&hmp->undo_lock);
d99d6bf5 MD	202
bf686dbe MD	203	if (buffer)
bf686dbe MD	204	hammer_rel_buffer(buffer, 0);
bf686dbe MD	205	return(error);
	206	}
	207
e8599db1 MD	208	/*
	209	* UNDO HISTORY API
	210	*
	211	* It is not necessary to layout an undo record for the same address space
	212	* multiple times. Maintain a cache of recent undo's.
	213	*/
	214
	215	/*
	216	* Enter an undo into the history. Return EALREADY if the request completely
	217	* covers a previous request.
	218	*/
	219	int
	220	hammer_enter_undo_history(hammer_mount_t hmp, hammer_off_t offset, int bytes)
	221	{
	222	hammer_undo_t node;
	223	hammer_undo_t onode;
	224
	225	node = RB_LOOKUP(hammer_und_rb_tree, &hmp->rb_undo_root, offset);
	226	if (node) {
	227	TAILQ_REMOVE(&hmp->undo_lru_list, node, lru_entry);
	228	TAILQ_INSERT_TAIL(&hmp->undo_lru_list, node, lru_entry);
	229	if (bytes <= node->bytes)
	230	return(EALREADY);
	231	node->bytes = bytes;
	232	return(0);
	233	}
	234	if (hmp->undo_alloc != HAMMER_MAX_UNDOS) {
	235	node = &hmp->undos[hmp->undo_alloc++];
	236	} else {
	237	node = TAILQ_FIRST(&hmp->undo_lru_list);
	238	TAILQ_REMOVE(&hmp->undo_lru_list, node, lru_entry);
	239	RB_REMOVE(hammer_und_rb_tree, &hmp->rb_undo_root, node);
	240	}
	241	node->offset = offset;
	242	node->bytes = bytes;
	243	TAILQ_INSERT_TAIL(&hmp->undo_lru_list, node, lru_entry);
	244	onode = RB_INSERT(hammer_und_rb_tree, &hmp->rb_undo_root, node);
	245	KKASSERT(onode == NULL);
	246	return(0);
	247	}
	248
	249	void
	250	hammer_clear_undo_history(hammer_mount_t hmp)
	251	{
	252	RB_INIT(&hmp->rb_undo_root);
	253	TAILQ_INIT(&hmp->undo_lru_list);
	254	hmp->undo_alloc = 0;
	255	}
	256
	257	/*
06ad81ff MD	258	* Return how much of the undo FIFO has been used
	259	*
	260	* The calculation includes undo FIFO space still reserved from a previous
	261	* flush (because it will still be run on recovery if a crash occurs and
	262	* we can't overwrite it yet).
e8599db1	263	*/
1f07f686	264	int64_t
06ad81ff	265	hammer_undo_used(hammer_transaction_t trans)
1f07f686	266	{
06ad81ff MD	267	hammer_blockmap_t cundomap;
06ad81ff MD	268	hammer_blockmap_t dundomap;
1f07f686	269	int64_t max_bytes;
c9b9e29d	270	int64_t bytes;
1f07f686	271
06ad81ff MD	272	cundomap = &trans->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
	273	dundomap = &trans->rootvol->ondisk->
	274	vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
1f07f686	275
06ad81ff MD	276	if (dundomap->first_offset <= cundomap->next_offset) {
06ad81ff MD	277	bytes = cundomap->next_offset - dundomap->first_offset;
1f07f686	278	} else {
06ad81ff MD	279	bytes = cundomap->alloc_offset - dundomap->first_offset +
06ad81ff MD	280	(cundomap->next_offset & HAMMER_OFF_LONG_MASK);
1f07f686	281	}
06ad81ff	282	max_bytes = cundomap->alloc_offset & HAMMER_OFF_SHORT_MASK;
c9b9e29d MD	283	KKASSERT(bytes <= max_bytes);
	284	return(bytes);
	285	}
	286
06ad81ff MD	287	/*
	288	* Return how much of the undo FIFO is available for new records.
	289	*/
c9b9e29d	290	int64_t
06ad81ff	291	hammer_undo_space(hammer_transaction_t trans)
c9b9e29d MD	292	{
	293	hammer_blockmap_t rootmap;
	294	int64_t max_bytes;
	295
06ad81ff	296	rootmap = &trans->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
c9b9e29d	297	max_bytes = rootmap->alloc_offset & HAMMER_OFF_SHORT_MASK;
06ad81ff	298	return(max_bytes - hammer_undo_used(trans));
1f07f686 MD	299	}
	300
	301	int64_t
	302	hammer_undo_max(hammer_mount_t hmp)
	303	{
	304	hammer_blockmap_t rootmap;
	305	int64_t max_bytes;
	306
	307	rootmap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
c9b9e29d	308	max_bytes = rootmap->alloc_offset & HAMMER_OFF_SHORT_MASK;
1f07f686 MD	309
	310	return(max_bytes);
	311	}
	312
e8599db1 MD	313	static int
	314	hammer_und_rb_compare(hammer_undo_t node1, hammer_undo_t node2)
	315	{
	316	if (node1->offset < node2->offset)
	317	return(-1);
	318	if (node1->offset > node2->offset)
	319	return(1);
	320	return(0);
	321	}
	322