/*
 * 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.
 */

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

#include "hammer.h"

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);
}

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 __debugvar;
        hammer_off_t result_offset;

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

        result_offset = hammer_xlate_to_undo(root_volume->ondisk, zone3_off);

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

/*
 * Generate UNDO record(s) 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.
 *
 * For HAMMER version 4+ UNDO a 512 byte boundary is enforced and a PAD
 * will be laid down for any unused space.  UNDO FIFO media structures
 * will implement the hdr_seq field (it used to be reserved01), and
 * both flush and recovery mechanics will be very different.
 *
 * WARNING!  See also hammer_generate_redo() in hammer_redo.c
 */
int
hammer_generate_undo(hammer_transaction_t trans,
                     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;
        int n;

        hmp = trans->hmp;

        /*
         * A SYNC record may be required before we can lay down a general
         * UNDO.  This ensures that the nominal recovery span contains
         * at least one SYNC record telling the recovery code how far
         * out-of-span it must go to run the REDOs.
         */
        if ((hmp->flags & HAMMER_MOUNT_REDO_SYNC) == 0 &&
            hmp->version >= HAMMER_VOL_VERSION_FOUR) {
                hammer_generate_redo_sync(trans);
        }

        /*
         * 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_noundo(NULL, root_volume);
        hammer_lock_ex(&hmp->undo_lock);

        /* undo had better not roll over (loose test) */
        if (hammer_undo_space(trans) < len + HAMMER_BUFSIZE*3)
                hpanic("insufficient UNDO/REDO FIFO space for undo!");

        /*
         * Loop until the undo for the entire range has been laid down.
         */
        while (len) {
                /*
                 * Fetch the layout offset in the UNDO FIFO, wrap it as
                 * necessary.
                 */
                if (undomap->next_offset == undomap->alloc_offset)
                        undomap->next_offset = HAMMER_ENCODE_UNDO(0);
                next_offset = undomap->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);
                        hammer_format_undo(hmp, undo,
                                           hmp->undo_seqno ^ 0x40000000);
                } else {
                        undo = hammer_bread(hmp, next_offset, &error, &buffer);
                }
                if (error)
                        break;
                /* no undo recursion */
                hammer_modify_buffer_noundo(NULL, buffer);

                /*
                 * Calculate how big a media structure fits up to the next
                 * alignment point and how large a data payload we can
                 * accomodate.
                 *
                 * If n calculates to 0 or negative there is no room for
                 * anything but a PAD.
                 */
                bytes = HAMMER_UNDO_ALIGN -
                        ((int)next_offset & HAMMER_UNDO_MASK);
                n = bytes -
                    (int)sizeof(struct hammer_fifo_undo) -
                    (int)sizeof(struct hammer_fifo_tail);

                /*
                 * If available space is insufficient for any payload
                 * we have to lay down a PAD.
                 *
                 * The minimum PAD is 8 bytes and the head and tail will
                 * overlap each other in that case.  PADs do not have
                 * sequence numbers or CRCs.
                 *
                 * A PAD may not start on a boundary.  That is, every
                 * 512-byte block in the UNDO/REDO FIFO must begin with
                 * a record containing a sequence number.
                 */
                if (n <= 0) {
                        KKASSERT(bytes >= sizeof(struct hammer_fifo_tail));
                        KKASSERT(((int)next_offset & HAMMER_UNDO_MASK) != 0);
                        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 OR SEQ NO */
                        undomap->next_offset += bytes;
                        hammer_modify_buffer_done(buffer);
                        hammer_stats_undo += bytes;
                        continue;
                }

                /*
                 * Calculate the actual payload and recalculate the size
                 * of the media structure as necessary.
                 */
                if (n > len) {
                        n = len;
                        bytes = HAMMER_HEAD_DOALIGN(n) +
                                (int)sizeof(struct hammer_fifo_undo) +
                                (int)sizeof(struct hammer_fifo_tail);
                }
                if (hammer_debug_general & 0x0080) {
                        hdkprintf("undo %016jx %d %d\n",
                                (intmax_t)next_offset, bytes, n);
                }

                undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
                undo->head.hdr_type = HAMMER_HEAD_TYPE_UNDO;
                undo->head.hdr_size = bytes;
                undo->head.hdr_seq = hmp->undo_seqno++;
                undo->head.hdr_crc = 0;
                undo->undo_offset = zone_off;
                undo->undo_data_bytes = n;
                bcopy(base, undo + 1, n);

                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));
                hammer_crc_set_fifo_head(hmp->version, &undo->head, bytes);
                undomap->next_offset += bytes;
                hammer_stats_undo += bytes;

                /*
                 * Before we finish off the buffer we have to deal with any
                 * junk between the end of the media structure we just laid
                 * down and the UNDO alignment boundary.  We do this by laying
                 * down a dummy PAD.  Even though we will probably overwrite
                 * it almost immediately we have to do this so recovery runs
                 * can iterate the UNDO space without having to depend on
                 * the indices in the volume header.
                 *
                 * This dummy PAD will be overwritten on the next undo so
                 * we do not adjust undomap->next_offset.
                 */
                bytes = HAMMER_UNDO_ALIGN -
                        ((int)undomap->next_offset & HAMMER_UNDO_MASK);
                if (bytes != HAMMER_UNDO_ALIGN) {
                        KKASSERT(bytes >= sizeof(struct hammer_fifo_tail));
                        undo = (void *)(tail + 1);
                        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 OR SEQ NO */
                }
                hammer_modify_buffer_done(buffer);

                /*
                 * Adjust for loop
                 */
                len -= n;
                base = (char *)base + n;
                zone_off += n;
        }
        hammer_modify_volume_done(root_volume);
        hammer_unlock(&hmp->undo_lock);

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

/*
 * Preformat a new UNDO block.  We could read the old one in but we get
 * better performance if we just pre-format a new one.
 *
 * The recovery code always works forwards so the caller just makes sure the
 * seqno is not contiguous with prior UNDOs or ancient UNDOs now being
 * overwritten.
 *
 * The preformatted UNDO headers use the smallest possible sector size
 * (512) to ensure that any missed media writes are caught.
 *
 * NOTE: Also used by the REDO code.
 */
void
hammer_format_undo(hammer_mount_t hmp, void *base, uint32_t seqno)
{
        hammer_fifo_head_t head;
        hammer_fifo_tail_t tail;
        int i;
        int bytes = HAMMER_UNDO_ALIGN;

        bzero(base, HAMMER_BUFSIZE);

        for (i = 0; i < HAMMER_BUFSIZE; i += bytes) {
                head = (void *)((char *)base + i);
                tail = (void *)((char *)head + bytes - sizeof(*tail));

                head->hdr_signature = HAMMER_HEAD_SIGNATURE;
                head->hdr_type = HAMMER_HEAD_TYPE_DUMMY;
                head->hdr_size = bytes;
                head->hdr_seq = seqno++;
                head->hdr_crc = 0;

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

                hammer_crc_set_fifo_head(hmp->version, head, bytes);
        }
}

/*
 * HAMMER version 4+ conversion support.
 *
 * Convert a HAMMER version < 4 UNDO FIFO area to a 4+ UNDO FIFO area.
 * The 4+ UNDO FIFO area is backwards compatible.  The conversion is
 * needed to initialize the sequence space and place headers on the
 * new 512-byte undo boundary.
 */
int
hammer_upgrade_undo_4(hammer_transaction_t trans)
{
        hammer_mount_t hmp;
        hammer_volume_t root_volume;
        hammer_blockmap_t undomap;
        hammer_buffer_t buffer = NULL;
        hammer_fifo_head_t head;
        hammer_fifo_tail_t tail;
        hammer_off_t next_offset;
        uint32_t seqno;
        int error;
        int bytes;

        hmp = trans->hmp;

        root_volume = trans->rootvol;

        /* no undo recursion */
        hammer_lock_ex(&hmp->undo_lock);
        hammer_modify_volume_noundo(NULL, root_volume);

        /*
         * Adjust the in-core undomap and the on-disk undomap.
         */
        next_offset = HAMMER_ENCODE_UNDO(0);
        undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
        undomap->next_offset = next_offset;
        undomap->first_offset = next_offset;

        undomap = &root_volume->ondisk->vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
        undomap->next_offset = next_offset;
        undomap->first_offset = next_offset;

        /*
         * Loop over the entire UNDO space creating DUMMY entries.  Sequence
         * numbers are assigned.
         */
        seqno = 0;
        bytes = HAMMER_UNDO_ALIGN;

        while (next_offset != undomap->alloc_offset) {
                head = hammer_bnew(hmp, next_offset, &error, &buffer);
                if (error)
                        break;
                hammer_modify_buffer_noundo(NULL, buffer);
                tail = (void *)((char *)head + bytes - sizeof(*tail));

                head->hdr_signature = HAMMER_HEAD_SIGNATURE;
                head->hdr_type = HAMMER_HEAD_TYPE_DUMMY;
                head->hdr_size = bytes;
                head->hdr_seq = seqno;
                head->hdr_crc = 0;

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

                hammer_crc_set_fifo_head(hmp->version, head, bytes);
                hammer_modify_buffer_done(buffer);

                hammer_stats_undo += bytes;
                next_offset += HAMMER_UNDO_ALIGN;
                ++seqno;
        }

        /*
         * The sequence number will be the next sequence number to lay down.
         */
        hmp->undo_seqno = seqno;
        hmkprintf(hmp, "version upgrade seqno start %08x\n", seqno);

        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 __debugvar;

        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 __debugvar;
        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 +
                        HAMMER_OFF_LONG_ENCODE(cundomap->next_offset);
        }
        max_bytes = HAMMER_OFF_SHORT_ENCODE(cundomap->alloc_offset);
        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 = HAMMER_OFF_SHORT_ENCODE(rootmap->alloc_offset);
        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 = HAMMER_OFF_SHORT_ENCODE(rootmap->alloc_offset);

        return(max_bytes);
}

/*
 * Returns 1 if the undo buffer should be reclaimed on release.  The
 * only undo buffer we do NOT want to reclaim is the one at the current
 * append offset.
 */
int
hammer_undo_reclaim(hammer_io_t io)
{
        hammer_blockmap_t undomap;
        hammer_off_t next_offset;

        undomap = &io->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
        next_offset = undomap->next_offset & ~HAMMER_BUFMASK64;
        if (HAMMER_ITOB(io)->zoneX_offset == next_offset)
                return(0);
        return(1);
}