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

/*
 * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * $DragonFly: src/sys/vfs/hammer/hammer_cursor.c,v 1.13 2008/01/17 05:06:09 dillon Exp $
 */

/*
 * HAMMER B-Tree index - cursor support routines
 */
#include "hammer.h"

static int hammer_load_cursor_parent(hammer_cursor_t cursor);
static int hammer_load_cursor_parent_local(hammer_cursor_t cursor);
static int hammer_load_cursor_parent_cluster(hammer_cursor_t cursor);

/*
 * Initialize a fresh cursor using the B-Tree node cache.  If the cache
 * is not available initialize a fresh cursor at the root of the root
 * cluster.
 */
int
hammer_init_cursor_hmp(hammer_cursor_t cursor, struct hammer_node **cache,
                       hammer_mount_t hmp)
{
        hammer_cluster_t cluster;
        hammer_node_t node;
        int error;

        bzero(cursor, sizeof(*cursor));

        /*
         * Step 1 - acquire a locked node from the cache if possible
         */
        if (cache && *cache) {
                node = hammer_ref_node_safe(hmp, cache, &error);
                if (error == 0) {
                        hammer_lock_ex(&node->lock);
                        if (node->flags & HAMMER_NODE_DELETED) {
                                hammer_unlock(&node->lock);
                                hammer_rel_node(node);
                                node = NULL;
                        }
                }
        } else {
                node = NULL;
        }

        /*
         * Step 2 - If we couldn't get a node from the cache, get
         * the one from the root of the root cluster.
         */
        while (node == NULL) {
                cluster = hammer_get_root_cluster(hmp, &error);
                if (error)
                        break;
                node = hammer_get_node(cluster,
                                       cluster->ondisk->clu_btree_root,
                                       &error);
                hammer_rel_cluster(cluster, 0);
                if (error)
                        break;
                hammer_lock_ex(&node->lock);
                if (node->flags & HAMMER_NODE_DELETED) {
                        hammer_unlock(&node->lock);
                        hammer_rel_node(node);
                        node = NULL;
                }
        }

        /*
         * Step 3 - finish initializing the cursor by acquiring the parent
         */
        cursor->node = node;
        if (error == 0)
                error = hammer_load_cursor_parent(cursor);
        KKASSERT(error == 0);
        return(error);
}

/*
 * Initialize a fresh cursor at the root of the specified cluster and
 * limit operations to within the cluster.
 */
int
hammer_init_cursor_cluster(hammer_cursor_t cursor, hammer_cluster_t cluster)
{
        int error;

        bzero(cursor, sizeof(*cursor));
        cursor->flags |= HAMMER_CURSOR_INCLUSTER;
        cursor->node = hammer_get_node(cluster,
                                       cluster->ondisk->clu_btree_root,
                                       &error);
        if (error == 0) {
                hammer_lock_ex(&cursor->node->lock);
                error = hammer_load_cursor_parent(cursor);
        }
        KKASSERT(error == 0);
        return(error);
}

/*
 * We are finished with a cursor.  We NULL out various fields as sanity
 * check, in case the structure is inappropriately used afterwords.
 */
void
hammer_done_cursor(hammer_cursor_t cursor)
{
        if (cursor->parent) {
                hammer_unlock(&cursor->parent->lock);
                hammer_rel_node(cursor->parent);
                cursor->parent = NULL;
        }
        if (cursor->node) {
                hammer_unlock(&cursor->node->lock);
                hammer_rel_node(cursor->node);
                cursor->node = NULL;
        }
        if (cursor->data_buffer) {
                hammer_rel_buffer(cursor->data_buffer, 0);
                cursor->data_buffer = NULL;
        }
        if (cursor->record_buffer) {
                hammer_rel_buffer(cursor->record_buffer, 0);
                cursor->record_buffer = NULL;
        }
        if (cursor->ip)
                hammer_mem_done(cursor);

        cursor->data = NULL;
        cursor->record = NULL;
        cursor->left_bound = NULL;
        cursor->right_bound = NULL;
}

/*
 * Acquire the parent B-Tree node of the specified node, returning a
 * referenced but unlocked node.  NULL can be returned with *errorp == 0
 * if node is the root node of the root cluster.
 */
static
hammer_node_t
hammer_get_parent_node(hammer_node_t node, int *errorp)
{
        hammer_cluster_t cluster;
        hammer_node_t parent;

        cluster = node->cluster;
        if (node->ondisk->parent) {
                /*
                 * Local parent
                 */
                parent = hammer_get_node(cluster, node->ondisk->parent, errorp);
        } else if (cluster->ondisk->clu_btree_parent_vol_no >= 0) {
                /*
                 * At cluster root, locate node in parent cluster
                 */
                hammer_cluster_ondisk_t ondisk;
                hammer_cluster_t pcluster;
                hammer_volume_t pvolume;
                int32_t clu_no;
                int32_t vol_no;

                ondisk = cluster->ondisk;
                vol_no = ondisk->clu_btree_parent_vol_no;
                clu_no = ondisk->clu_btree_parent_clu_no;

                /*
                 * Acquire the node from (volume, cluster, offset)
                 */
                pvolume = hammer_get_volume(cluster->volume->hmp, vol_no,
                                            errorp);
                if (*errorp)
                        return (NULL);
                pcluster = hammer_get_cluster(pvolume, clu_no, errorp, 0);
                hammer_rel_volume(pvolume, 0);
                if (*errorp)
                        return (NULL);
                parent = hammer_get_node(pcluster,
                                         ondisk->clu_btree_parent_offset,
                                         errorp);
                hammer_rel_cluster(pcluster, 0);
        } else {
                /*
                 * At root of root cluster, there is no parent.
                 */
                KKASSERT(cluster->ondisk->clu_btree_parent_vol_no == -1);
                parent = NULL;
                *errorp = 0;
        }
        return(parent);
}

/*
 * Load the parent of cursor->node into cursor->parent.  There are several
 * cases.  (1) The parent is in the current cluster.  (2) We are at the
 * root of the cluster and the parent is in another cluster.  (3) We are at
 * the root of the root cluster.
 *
 * If HAMMER_CURSOR_INCLUSTER is set and we are at the root of the cluster,
 * we do not access the parent cluster at all and make the cursor look like
 * its at the root.
 */
static
int
hammer_load_cursor_parent(hammer_cursor_t cursor)
{
        hammer_cluster_t cluster;
        int error;

        cluster = cursor->node->cluster;

        if (cursor->node->ondisk->parent) {
                error = hammer_load_cursor_parent_local(cursor);
        } else if (cluster->ondisk->clu_btree_parent_vol_no >= 0 &&
                   ((cursor->flags & HAMMER_CURSOR_INCLUSTER) == 0)
        ) {
                error = hammer_load_cursor_parent_cluster(cursor);
        } else {
                cursor->parent = NULL;
                cursor->parent_index = 0;
                cursor->left_bound = &cluster->ondisk->clu_btree_beg;
                cursor->right_bound = &cluster->ondisk->clu_btree_end;
                error = 0;
        }
        return(error);
}

static
int
hammer_load_cursor_parent_local(hammer_cursor_t cursor)
{
        hammer_node_t node;
        hammer_node_t parent;
        hammer_btree_elm_t elm;
        int error;
        int i;

        node = cursor->node;
        parent = hammer_get_node(node->cluster, node->ondisk->parent, &error);
        if (error)
                return(error);
        elm = NULL;
        for (i = 0; i < parent->ondisk->count; ++i) {
                elm = &parent->ondisk->elms[i];
                if (parent->ondisk->elms[i].internal.subtree_offset ==
                    node->node_offset) {
                        break;
                }
        }
        if (i == parent->ondisk->count)
                panic("Bad B-Tree link: parent %p node %p\n", parent, node);
        KKASSERT(i != parent->ondisk->count);
        cursor->parent = parent;
        cursor->parent_index = i;
        cursor->left_bound = &elm[0].internal.base;
        cursor->right_bound = &elm[1].internal.base;

        if (hammer_lock_ex_try(&parent->lock) != 0) {
                hammer_unlock(&cursor->node->lock);
                hammer_lock_ex(&parent->lock);
                hammer_lock_ex(&cursor->node->lock);
                /* XXX check node generation count */
        }
        return(error);
}

static
int
hammer_load_cursor_parent_cluster(hammer_cursor_t cursor)
{
        hammer_cluster_ondisk_t ondisk;
        hammer_cluster_t pcluster;
        hammer_cluster_t ccluster;
        hammer_volume_t volume;
        hammer_node_t node;
        hammer_node_t parent;
        hammer_btree_elm_t elm;
        int32_t clu_no;
        int32_t vol_no;
        int error;
        int i;

        node = cursor->node;
        ccluster = node->cluster;
        ondisk = ccluster->ondisk;
        vol_no = ondisk->clu_btree_parent_vol_no;
        clu_no = ondisk->clu_btree_parent_clu_no;

        /*
         * Acquire the node from (volume, cluster, offset).  This should
         * be a leaf node containing the HAMMER_BTREE_TYPE_SPIKE_END element.
         */
        volume = hammer_get_volume(ccluster->volume->hmp, vol_no, &error);
        if (error)
                return (error);
        pcluster = hammer_get_cluster(volume, clu_no, &error, 0);
        hammer_rel_volume(volume, 0);
        if (error)
                return (error);
        parent = hammer_get_node(pcluster, ondisk->clu_btree_parent_offset,
                                 &error);
        hammer_rel_cluster(pcluster, 0);
        if (error)
                return (error);
        KKASSERT(parent->ondisk->type == HAMMER_BTREE_TYPE_LEAF);

        /* 
         * Ok, we have the node.  Locate the inter-cluster element
         */
        elm = NULL;
        for (i = 0; i < parent->ondisk->count; ++i) {
                elm = &parent->ondisk->elms[i];

                if (elm->leaf.base.btype == HAMMER_BTREE_TYPE_SPIKE_END &&
                    elm->leaf.spike_clu_no == cursor->node->cluster->clu_no) {
                        break;
                }
        }
        KKASSERT(i != parent->ondisk->count);
        KKASSERT(i && elm[-1].leaf.base.btype == HAMMER_BTREE_TYPE_SPIKE_BEG);
        cursor->parent = parent;
        cursor->parent_index = i;
        cursor->left_bound = &ccluster->ondisk->clu_btree_beg;
        cursor->right_bound = &ccluster->ondisk->clu_btree_end;

        KKASSERT(hammer_btree_cmp(&elm[-1].leaf.base,
                 &ccluster->ondisk->clu_btree_beg) == 0);
            /*
             * spike_end is an inclusive boundary and will != clu_btree_end
        KKASSERT(hammer_btree_cmp(cursor->right_bound,
                 &ccluster->ondisk->clu_btree_end) >= 0);
            */

        if (hammer_lock_ex_try(&parent->lock) != 0) {
                hammer_unlock(&cursor->node->lock);
                hammer_lock_ex(&parent->lock);
                hammer_lock_ex(&cursor->node->lock);
                /* XXX check node generation count */
        }
        return(0);
}

/*
 * Cursor up to our parent node.  Return ENOENT if we are at the root of
 * the root cluster.
 *
 * If doing a nonblocking cursor-up and we are unable to acquire the lock,
 * the cursor remains unchanged.
 */
int
hammer_cursor_up(hammer_cursor_t cursor, int nonblock)
{
        hammer_node_t save;
        int error;

        /*
         * If asked to do this non-blocking acquire a lock on the parent
         * now, before we mess with the cursor.
         */
        if (nonblock) {
                save = hammer_get_parent_node(cursor->parent, &error);
                if (error)
                        return(error);
                if (save) {
                        if (hammer_lock_ex_try(&save->lock) != 0) {
                                hammer_rel_node(save);
                                return(EAGAIN);
                        }
                }
        } else {
                save = NULL;
        }

        /*
         * Set the node to its parent.  If the parent is NULL we are at
         * the root of the root cluster and return ENOENT.
         */
        hammer_unlock(&cursor->node->lock);
        hammer_rel_node(cursor->node);
        cursor->node = cursor->parent;
        cursor->index = cursor->parent_index;
        cursor->parent = NULL;
        cursor->parent_index = 0;

        if (cursor->node == NULL) {
                error = ENOENT;
        } else if ((cursor->flags & HAMMER_CURSOR_INCLUSTER) &&
                   cursor->node->ondisk->parent == 0
        ) {
                error = ENOENT;
        } else {
                error = hammer_load_cursor_parent(cursor);
        }
        if (save) {
                hammer_unlock(&save->lock);
                hammer_rel_node(save);
        }
        return(error);
}

/*
 * Set the cursor to the root of the current cursor's cluster.
 */
int
hammer_cursor_toroot(hammer_cursor_t cursor)
{
        hammer_cluster_t cluster;
        int error;

        /*
         * Already at root of cluster?
         */
        if (cursor->node->ondisk->parent == 0) 
                return (0);

        /*
         * Parent is root of cluster?
         */
        if (cursor->parent->ondisk->parent == 0)
                return (hammer_cursor_up(cursor, 0));

        /*
         * Ok, reload the cursor with the root of the cluster, then
         * locate its parent.
         */
        cluster = cursor->node->cluster;
        error = hammer_ref_cluster(cluster);
        if (error)
                return (error);

        hammer_unlock(&cursor->parent->lock);
        hammer_rel_node(cursor->parent);
        hammer_unlock(&cursor->node->lock);
        hammer_rel_node(cursor->node);
        cursor->parent = NULL;
        cursor->parent_index = 0;

        cursor->node = hammer_get_node(cluster, cluster->ondisk->clu_btree_root,
                                       &error);
        cursor->index = 0;
        hammer_lock_ex(&cursor->node->lock);
        hammer_rel_cluster(cluster, 0);
        if (error == 0)
                error = hammer_load_cursor_parent(cursor);
        return(error);
}

/*
 * Cursor down through the current node, which must be an internal node.
 *
 * This routine adjusts the cursor and sets index to 0.
 */
int
hammer_cursor_down(hammer_cursor_t cursor)
{
        hammer_node_t node;
        hammer_btree_elm_t elm;
        hammer_volume_t volume;
        hammer_cluster_t cluster;
        int32_t vol_no;
        int32_t clu_no;
        int error;

        /*
         * The current node becomes the current parent
         */
        node = cursor->node;
        KKASSERT(cursor->index >= 0 && cursor->index < node->ondisk->count);
        if (cursor->parent) {
                hammer_unlock(&cursor->parent->lock);
                hammer_rel_node(cursor->parent);
        }
        cursor->parent = node;
        cursor->parent_index = cursor->index;
        cursor->node = NULL;
        cursor->index = 0;

        /*
         * Extract element to push into at (node,index), set bounds.
         */
        elm = &node->ondisk->elms[cursor->parent_index];

        /*
         * Ok, push down into elm.  If elm specifies an internal or leaf
         * node the current node must be an internal node.  If elm specifies
         * a spike then the current node must be a leaf node.
         *
         * Cursoring down through a cluster transition when the INCLUSTER
         * flag is set is not legal.
         */
        switch(elm->base.btype) {
        case HAMMER_BTREE_TYPE_INTERNAL:
        case HAMMER_BTREE_TYPE_LEAF:
                KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
                KKASSERT(elm->internal.subtree_offset != 0);
                cursor->left_bound = &elm[0].internal.base;
                cursor->right_bound = &elm[1].internal.base;
                node = hammer_get_node(node->cluster,
                                       elm->internal.subtree_offset,
                                       &error);
                if (error == 0) {
                        KKASSERT(elm->base.btype == node->ondisk->type);
                        if(node->ondisk->parent != cursor->parent->node_offset)
                                kprintf("node %p %d vs %d\n", node, node->ondisk->parent, cursor->parent->node_offset);
                        KKASSERT(node->ondisk->parent == cursor->parent->node_offset);
                }
                break;
        case HAMMER_BTREE_TYPE_SPIKE_BEG:
        case HAMMER_BTREE_TYPE_SPIKE_END:
                KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_LEAF);
                KKASSERT((cursor->flags & HAMMER_CURSOR_INCLUSTER) == 0);
                vol_no = elm->leaf.spike_vol_no;
                clu_no = elm->leaf.spike_clu_no;
                volume = hammer_get_volume(node->cluster->volume->hmp,
                                           vol_no, &error);
                KKASSERT(error != EINVAL);
                if (error)
                        return(error);
                cluster = hammer_get_cluster(volume, clu_no, &error, 0);
                KKASSERT(error != EINVAL);
                hammer_rel_volume(volume, 0);
                if (error)
                        return(error);
                cursor->left_bound = &cluster->ondisk->clu_btree_beg;
                cursor->right_bound = &cluster->ondisk->clu_btree_end;
                node = hammer_get_node(cluster,
                                       cluster->ondisk->clu_btree_root,
                                       &error);
                hammer_rel_cluster(cluster, 0);
                break;
        default:
                panic("hammer_cursor_down: illegal btype %02x (%c)\n",
                      elm->base.btype,
                      (elm->base.btype ? elm->base.btype : '?'));
                break;
        }
        if (error == 0) {
                hammer_lock_ex(&node->lock);
                cursor->node = node;
                cursor->index = 0;
        }
        return(error);
}