hammer2 - Start work on inode indexing - MAJOR CHANGE

[dragonfly.git] / sys / vfs / hammer2 / hammer2_xops.c

/*
 * Copyright (c) 2011-2015 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@dragonflybsd.org>
 * by Venkatesh Srinivas <vsrinivas@dragonflybsd.org>
 * by Daniel Flores (GSOC 2013 - mentored by Matthew Dillon, compression) 
 *
 * 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.
 */
/*
 * Per-node backend for kernel filesystem interface.
 *
 * This executes a VOP concurrently on multiple nodes, each node via its own
 * thread, and competes to advance the original request.  The original
 * request is retired the moment all requirements are met, even if the
 * operation is still in-progress on some nodes.
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/fcntl.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/mountctl.h>
#include <sys/dirent.h>
#include <sys/uio.h>
#include <sys/objcache.h>
#include <sys/event.h>
#include <sys/file.h>
#include <vfs/fifofs/fifo.h>

#include "hammer2.h"

/*
 * Determine if the specified directory is empty.  Returns 0 on success.
 */
static
int
checkdirempty(hammer2_chain_t *orig_parent)
{
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        int cache_index = -1;
        int error;

        parent = hammer2_chain_lookup_init(orig_parent, 0);
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     HAMMER2_DIRHASH_VISIBLE,
                                     HAMMER2_KEY_MAX,
                                     &cache_index, 0);
        error = chain ? ENOTEMPTY : 0;
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
        hammer2_chain_lookup_done(parent);

        return error;
}

/*
 * Backend for hammer2_vfs_root()
 *
 * This is called when a newly mounted PFS has not yet synchronized
 * to the inode_tid and modify_tid.
 */
void
hammer2_xop_ipcluster(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_ipcluster_t *xop = &arg->xop_ipcluster;
        hammer2_chain_t *chain;
        int error;

        chain = hammer2_inode_chain(xop->head.ip1, clindex,
                                    HAMMER2_RESOLVE_ALWAYS |
                                    HAMMER2_RESOLVE_SHARED);
        if (chain)
                error = chain->error;
        else
                error = EIO;
                
        hammer2_xop_feed(&xop->head, chain, clindex, error);
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
}

/*
 * Backend for hammer2_vop_readdir()
 */
void
hammer2_xop_readdir(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_readdir_t *xop = &arg->xop_readdir;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        hammer2_key_t lkey;
        int cache_index = -1;
        int error = 0;

        lkey = xop->lkey;
        if (hammer2_debug & 0x0020)
                kprintf("xop_readdir %p lkey=%016jx\n", xop, lkey);

        /*
         * The inode's chain is the iterator.  If we cannot acquire it our
         * contribution ends here.
         */
        parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        if (parent == NULL) {
                kprintf("xop_readdir: NULL parent\n");
                goto done;
        }

        /*
         * Directory scan [re]start and loop, the feed inherits the chain's
         * lock so do not unlock it on the iteration.
         */
        chain = hammer2_chain_lookup(&parent, &key_next, lkey, lkey,
                                     &cache_index, HAMMER2_LOOKUP_SHARED);
        if (chain == NULL) {
                chain = hammer2_chain_lookup(&parent, &key_next,
                                             lkey, HAMMER2_KEY_MAX,
                                             &cache_index,
                                             HAMMER2_LOOKUP_SHARED);
        }
        while (chain) {
                error = hammer2_xop_feed(&xop->head, chain, clindex, 0);
                if (error)
                        break;
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, HAMMER2_KEY_MAX,
                                           &cache_index,
                                           HAMMER2_LOOKUP_SHARED);
        }
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
        hammer2_chain_unlock(parent);
        hammer2_chain_drop(parent);
done:
        hammer2_xop_feed(&xop->head, NULL, clindex, error);
}

/*
 * Backend for hammer2_vop_nresolve()
 */
void
hammer2_xop_nresolve(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_nresolve_t *xop = &arg->xop_nresolve;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        const hammer2_inode_data_t *ripdata;
        const char *name;
        size_t name_len;
        hammer2_key_t key_next;
        hammer2_key_t lhc;
        int cache_index = -1;   /* XXX */
        int error;

        parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        if (parent == NULL) {
                kprintf("xop_nresolve: NULL parent\n");
                chain = NULL;
                error = EIO;
                goto done;
        }
        name = xop->head.name1;
        name_len = xop->head.name1_len;

        /*
         * Lookup the directory entry
         */
        lhc = hammer2_dirhash(name, name_len);
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     lhc, lhc + HAMMER2_DIRHASH_LOMASK,
                                     &cache_index,
                                     HAMMER2_LOOKUP_ALWAYS |
                                     HAMMER2_LOOKUP_SHARED);
        while (chain) {
                ripdata = &chain->data->ipdata;
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                    ripdata->meta.name_len == name_len &&
                    bcmp(ripdata->filename, name, name_len) == 0) {
                        break;
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next,
                                           lhc + HAMMER2_DIRHASH_LOMASK,
                                           &cache_index,
                                           HAMMER2_LOOKUP_ALWAYS |
                                           HAMMER2_LOOKUP_SHARED);
        }

        /*
         * If the entry is a hardlink pointer, resolve it.
         */
        error = 0;
        if (chain) {
                if (chain->data->ipdata.meta.type == HAMMER2_OBJTYPE_HARDLINK) {
                        error = hammer2_chain_hardlink_find(
                                                xop->head.ip1,
                                                &parent, &chain,
                                                HAMMER2_LOOKUP_SHARED);
                }
        }
done:
        error = hammer2_xop_feed(&xop->head, chain, clindex, error);
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
}

/*
 * Backend for hammer2_vop_nremove(), hammer2_vop_nrmdir(), and helper
 * for hammer2_vop_nrename().
 *
 * This function locates and removes the directory entry.  If the
 * entry is a hardlink pointer, this function will also remove the
 * hardlink target if the target's nlinks is 1.
 *
 * The frontend is responsible for moving open inodes to the hidden directory
 * and for decrementing nlinks.
 */
void
hammer2_xop_unlink(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_unlink_t *xop = &arg->xop_unlink;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        const hammer2_inode_data_t *ripdata;
        const char *name;
        size_t name_len;
        hammer2_key_t key_next;
        hammer2_key_t lhc;
        int cache_index = -1;   /* XXX */
        int error;

        /*
         * Requires exclusive lock
         */
        parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                     HAMMER2_RESOLVE_ALWAYS);
        chain = NULL;
        if (parent == NULL) {
                kprintf("xop_nresolve: NULL parent\n");
                error = EIO;
                goto done;
        }
        name = xop->head.name1;
        name_len = xop->head.name1_len;

        /*
         * Lookup the directory entry
         */
        lhc = hammer2_dirhash(name, name_len);
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     lhc, lhc + HAMMER2_DIRHASH_LOMASK,
                                     &cache_index,
                                     HAMMER2_LOOKUP_ALWAYS);
        while (chain) {
                ripdata = &chain->data->ipdata;
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                    ripdata->meta.name_len == name_len &&
                    bcmp(ripdata->filename, name, name_len) == 0) {
                        break;
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next,
                                           lhc + HAMMER2_DIRHASH_LOMASK,
                                           &cache_index,
                                           HAMMER2_LOOKUP_ALWAYS);
        }

        /*
         * If the directory entry is a HARDLINK pointer then obtain the
         * underlying file type for the directory typing tests and delete
         * the HARDLINK pointer chain permanently.  The frontend is left
         * responsible for handling nlinks on and deleting the actual inode.
         *
         * If the directory entry is the actual inode then use its type
         * for the directory typing tests and delete the chain, permanency
         * depends on whether the inode is open or not.
         *
         * Check directory typing and delete the entry.  Note that
         * nlinks adjustments are made on the real inode by the frontend,
         * not here.
         */
        error = 0;
        if (chain) {
                int dopermanent = xop->dopermanent;
                uint8_t type;

                type = chain->data->ipdata.meta.type;
                if (type == HAMMER2_OBJTYPE_HARDLINK) {
                        type = chain->data->ipdata.meta.target_type;
                        dopermanent |= HAMMER2_DELETE_PERMANENT;
                }

                if (type == HAMMER2_OBJTYPE_DIRECTORY &&
                    checkdirempty(chain) != 0) {
                        error = ENOTEMPTY;
                } else if (type == HAMMER2_OBJTYPE_DIRECTORY &&
                    xop->isdir == 0) {
                        error = ENOTDIR;
                } else 
                if (type != HAMMER2_OBJTYPE_DIRECTORY &&
                    xop->isdir >= 1) {
                        error = EISDIR;
                } else {
                        /*
                         * This deletes the directory entry itself, which is
                         * also the inode when nlinks == 1.  Hardlink targets
                         * are handled in the next conditional.
                         */
                        error = chain->error;
                        hammer2_chain_delete(parent, chain,
                                             xop->head.mtid, dopermanent);
                }
        }

        /*
         * If the entry is a hardlink pointer, resolve it.  If this is the
         * last link, delete it.  The frontend has the master copy of nlinks
         * but we still have to make adjustments here to synchronize with it.
         *
         * On delete / adjust nlinks if there is no error.  But we still need
         * to resolve the hardlink to feed the inode's real chain back to
         * the frontend.
         *
         * XXX we are basically tracking the nlinks count by doing a delta
         *     adjustment instead of having the frontend pass the absolute
         *     value down.  We really need to have the frontend pass the
         *     absolute value down (difficult because there might not be
         *     an 'ip').  See also hammer2_xop_nlink().
         */
        if (chain &&
            chain->data->ipdata.meta.type == HAMMER2_OBJTYPE_HARDLINK) {
                int error2;

                error2 = hammer2_chain_hardlink_find(xop->head.ip1,
                                                     &parent, &chain, 0);
                if (chain && error == 0 && error2 == 0 &&
                    (int64_t)chain->data->ipdata.meta.nlinks <= 1) {
                        hammer2_chain_delete(parent, chain,
                                             xop->head.mtid,
                                             xop->dopermanent);
                } else if (chain && error == 0 && error2 == 0) {
                        hammer2_chain_modify(chain, xop->head.mtid, 0, 0);
                        --chain->data->ipdata.meta.nlinks;
                }
                if (error == 0)
                        error = error2;
        }

        /*
         * Chains passed to feed are expected to be locked shared.
         */
        if (chain)
                hammer2_chain_lock_downgrade(chain);

        /*
         * We always return the hardlink target (the real inode) for
         * further action.
         */
done:
        hammer2_xop_feed(&xop->head, chain, clindex, error);
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
                chain = NULL;
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
                parent = NULL;
        }
}

#if 0
/*
 * Backend for hammer2_vop_nlink() and hammer2_vop_nrename()
 *
 * ip1 - fdip
 * ip2 - ip
 * ip3 - cdip
 *
 * If a hardlink pointer:
 *      The existing hardlink target {fdip,ip} must be moved to another
 *      directory {cdip,ip}
 *
 * If not a hardlink pointer:
 *      Convert the target {fdip,ip} to a hardlink target {cdip,ip} and
 *      replace the original namespace {fdip,name} with a hardlink pointer.
 */
void
hammer2_xop_nlink(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_nlink_t *xop = &arg->xop_nlink;
        hammer2_pfs_t *pmp;
        hammer2_inode_data_t *wipdata;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_chain_t *tmp;
        hammer2_inode_t *ip;
        hammer2_key_t key_dummy;
        int cache_index = -1;
        int error;
        int did_delete = 0;

        /*
         * We need the precise parent chain to issue the deletion.
         */
        ip = xop->head.ip2;
        pmp = ip->pmp;
        parent = hammer2_inode_chain(ip, clindex, HAMMER2_RESOLVE_ALWAYS);
        if (parent)
                hammer2_chain_getparent(&parent, HAMMER2_RESOLVE_ALWAYS);
        if (parent == NULL) {
                chain = NULL;
                error = EIO;
                goto done;
        }
        chain = hammer2_inode_chain(ip, clindex, HAMMER2_RESOLVE_ALWAYS);
        if (chain == NULL) {
                error = EIO;
                goto done;
        }
        KKASSERT(chain->parent == parent);

        if (chain->data->ipdata.meta.name_key & HAMMER2_DIRHASH_VISIBLE) {
                /*
                 * Delete the original chain and hold onto it for the move
                 * to cdir.
                 *
                 * Replace the namespace with a hardlink pointer if the
                 * chain being moved is not already a hardlink target.
                 */
                hammer2_chain_delete(parent, chain, xop->head.mtid, 0);
                did_delete = 1;

                tmp = NULL;
                error = hammer2_chain_create(&parent, &tmp, pmp,
                                             chain->bref.key, 0,
                                             HAMMER2_BREF_TYPE_INODE,
                                             HAMMER2_INODE_BYTES,
                                             xop->head.mtid, 0, 0);
                if (error)
                        goto done;
                hammer2_chain_modify(tmp, xop->head.mtid, 0, 0);
                wipdata = &tmp->data->ipdata;
                bzero(wipdata, sizeof(*wipdata));
                wipdata->meta.name_key = chain->data->ipdata.meta.name_key;
                wipdata->meta.name_len = chain->data->ipdata.meta.name_len;
                bcopy(chain->data->ipdata.filename, wipdata->filename,
                      chain->data->ipdata.meta.name_len);
                wipdata->meta.target_type = chain->data->ipdata.meta.type;
                wipdata->meta.type = HAMMER2_OBJTYPE_HARDLINK;
                wipdata->meta.inum = ip->meta.inum;
                wipdata->meta.version = HAMMER2_INODE_VERSION_ONE;
                wipdata->meta.nlinks = 1;
                wipdata->meta.op_flags = HAMMER2_OPFLAG_DIRECTDATA;

                hammer2_chain_unlock(tmp);
                hammer2_chain_drop(tmp);
        } else if (xop->head.ip1 != xop->head.ip3) {
                /*
                 * Delete the hardlink target so it can be moved
                 * to cdir.
                 */
                hammer2_chain_delete(parent, chain, xop->head.mtid, 0);
                did_delete = 1;
        } else {
                /*
                 * Deletion not necessary (just a nlinks update).
                 */
                did_delete = 0;
        }

        hammer2_chain_unlock(parent);
        hammer2_chain_drop(parent);
        parent = NULL;

        /*
         * Ok, back to the deleted chain.  We must reconnect this chain
         * as a hardlink target to cdir (ip3).
         *
         * WARNING! Frontend assumes filename length is 18 bytes.
         */
        if (did_delete) {
                hammer2_chain_modify(chain, xop->head.mtid, 0, 0);
                wipdata = &chain->data->ipdata;
                ksnprintf(wipdata->filename, sizeof(wipdata->filename),
                          "0x%016jx", (intmax_t)ip->meta.inum);
                wipdata->meta.name_len = strlen(wipdata->filename);
                wipdata->meta.name_key = ip->meta.inum;

                /*
                 * We must seek parent properly for the create to reattach
                 * chain.  XXX just use chain->parent or
                 * inode_chain_and_parent() ?
                 */
                parent = hammer2_inode_chain(xop->head.ip3, clindex,
                                             HAMMER2_RESOLVE_ALWAYS);
                if (parent == NULL) {
                        error = EIO;
                        goto done;
                }
                tmp = hammer2_chain_lookup(&parent, &key_dummy,
                                           ip->meta.inum, ip->meta.inum,
                                           &cache_index, 0);
                if (tmp) {
                        hammer2_chain_unlock(tmp);
                        hammer2_chain_drop(tmp);
                        error = EEXIST;
                        goto done;
                }
                error = hammer2_chain_create(&parent, &chain, pmp,
                                             wipdata->meta.name_key, 0,
                                             HAMMER2_BREF_TYPE_INODE,
                                             HAMMER2_INODE_BYTES,
                                             xop->head.mtid, 0, 0);
        } else {
                error = 0;
        }

        /*
         * Bump nlinks to synchronize with frontend.
         */
        if (xop->nlinks_delta) {
                hammer2_chain_modify(chain, xop->head.mtid, 0, 0);
                chain->data->ipdata.meta.nlinks += xop->nlinks_delta;
        }

        /*
         * To avoid having to scan the collision space we can simply
         * reuse the inode's original name_key.  But ip->meta.name_key
         * may have already been updated by the front-end, so use xop->lhc.
         *
         * (frontend is responsible for fixing up ip->pip).
         */
done:
        hammer2_xop_feed(&xop->head, NULL, clindex, error);
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
}
#endif

/*
 * Backend for hammer2_vop_nrename()
 *
 * This handles the final step of renaming, either renaming the
 * actual inode or renaming the hardlink pointer.
 */
void
hammer2_xop_nrename(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_nrename_t *xop = &arg->xop_nrename;
        hammer2_pfs_t *pmp;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_chain_t *tmp;
        hammer2_inode_t *ip;
        hammer2_key_t key_dummy;
        int cache_index = -1;
        int error;

        /*
         * We need the precise parent chain to issue the deletion.
         *
         * If this is not a hardlink target we can act on the inode,
         * otherwise we have to locate the hardlink pointer.
         */
        ip = xop->head.ip2;
        pmp = ip->pmp;
        chain = NULL;

        if (xop->ip_key & HAMMER2_DIRHASH_VISIBLE) {
                /*
                 * Find ip's direct parent chain.
                 */
                parent = hammer2_inode_chain(ip, clindex,
                                             HAMMER2_RESOLVE_ALWAYS);
                if (parent)
                        hammer2_chain_getparent(&parent,
                                                HAMMER2_RESOLVE_ALWAYS);
                if (parent == NULL) {
                        error = EIO;
                        goto done;
                }
                chain = hammer2_inode_chain(ip, clindex,
                                            HAMMER2_RESOLVE_ALWAYS);
                if (chain == NULL) {
                        error = EIO;
                        goto done;
                }
        } else {
                /*
                 * The hardlink pointer for the head.ip1 hardlink target
                 * is in fdip, do a namespace search.
                 */
                const hammer2_inode_data_t *ripdata;
                hammer2_key_t lhc;
                hammer2_key_t key_next;
                const char *name;
                size_t name_len;

                parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                             HAMMER2_RESOLVE_ALWAYS);
                if (parent == NULL) {
                        kprintf("xop_nrename: NULL parent\n");
                        error = EIO;
                        goto done;
                }
                name = xop->head.name1;
                name_len = xop->head.name1_len;

                /*
                 * Lookup the directory entry
                 */
                lhc = hammer2_dirhash(name, name_len);
                chain = hammer2_chain_lookup(&parent, &key_next,
                                             lhc, lhc + HAMMER2_DIRHASH_LOMASK,
                                             &cache_index,
                                             HAMMER2_LOOKUP_ALWAYS);
                while (chain) {
                        ripdata = &chain->data->ipdata;
                        if (chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                            ripdata->meta.name_len == name_len &&
                            bcmp(ripdata->filename, name, name_len) == 0) {
                                break;
                        }
                        chain = hammer2_chain_next(&parent, chain, &key_next,
                                                   key_next,
                                                   lhc + HAMMER2_DIRHASH_LOMASK,
                                                   &cache_index,
                                                   HAMMER2_LOOKUP_ALWAYS);
                }
        }

        if (chain == NULL) {
                /* XXX shouldn't happen, but does under fsstress */
                kprintf("hammer2_xop_rename: \"%s\" -> \"%s\"  ENOENT\n",
                        xop->head.name1,
                        xop->head.name2);
                error = ENOENT;
                goto done;
        }

        /*
         * Delete it, then create it in the new namespace.
         */
        hammer2_chain_delete(parent, chain, xop->head.mtid, 0);
        hammer2_chain_unlock(parent);
        hammer2_chain_drop(parent);
        parent = NULL;          /* safety */

        /*
         * Ok, back to the deleted chain.  We must reconnect this chain
         * to tdir (ip3).  The chain (a real inode or a hardlink pointer)
         * is not otherwise modified.
         *
         * Frontend is expected to replicate the same inode meta data
         * modifications.
         *
         * NOTE!  This chain may not represent the actual inode, it
         *        can be a hardlink pointer.
         *
         * XXX in-inode parent directory specification?
         */
        if (chain->data->ipdata.meta.name_key != xop->lhc ||
            xop->head.name1_len != xop->head.name2_len ||
            bcmp(xop->head.name1, xop->head.name2, xop->head.name1_len) != 0) {
                hammer2_inode_data_t *wipdata;

                hammer2_chain_modify(chain, xop->head.mtid, 0, 0);
                wipdata = &chain->data->ipdata;

                bzero(wipdata->filename, sizeof(wipdata->filename));
                bcopy(xop->head.name2, wipdata->filename, xop->head.name2_len);
                wipdata->meta.name_key = xop->lhc;
                wipdata->meta.name_len = xop->head.name2_len;
        }

        /*
         * We must seek parent properly for the create.
         */
        parent = hammer2_inode_chain(xop->head.ip3, clindex,
                                     HAMMER2_RESOLVE_ALWAYS);
        if (parent == NULL) {
                error = EIO;
                goto done;
        }
        tmp = hammer2_chain_lookup(&parent, &key_dummy,
                                   xop->lhc, xop->lhc,
                                   &cache_index, 0);
        if (tmp) {
                hammer2_chain_unlock(tmp);
                hammer2_chain_drop(tmp);
                error = EEXIST;
                goto done;
        }

        error = hammer2_chain_create(&parent, &chain, pmp,
                                     xop->lhc, 0,
                                     HAMMER2_BREF_TYPE_INODE,
                                     HAMMER2_INODE_BYTES,
                                     xop->head.mtid, 0, 0);
        /*
         * (frontend is responsible for fixing up ip->pip).
         */
done:
        hammer2_xop_feed(&xop->head, NULL, clindex, error);
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
}

/*
 * Directory collision resolver scan helper (backend, threaded).
 *
 * Used by the inode create code to locate an unused lhc.
 */
void
hammer2_xop_scanlhc(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_scanlhc_t *xop = &arg->xop_scanlhc;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        int cache_index = -1;   /* XXX */
        int error = 0;

        parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        if (parent == NULL) {
                kprintf("xop_nresolve: NULL parent\n");
                chain = NULL;
                error = EIO;
                goto done;
        }

        /*
         * Lookup all possibly conflicting directory entries, the feed
         * inherits the chain's lock so do not unlock it on the iteration.
         */
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     xop->lhc,
                                     xop->lhc + HAMMER2_DIRHASH_LOMASK,
                                     &cache_index,
                                     HAMMER2_LOOKUP_ALWAYS |
                                     HAMMER2_LOOKUP_SHARED);
        while (chain) {
                error = hammer2_xop_feed(&xop->head, chain, clindex,
                                         chain->error);
                if (error) {
                        hammer2_chain_unlock(chain);
                        hammer2_chain_drop(chain);
                        chain = NULL;   /* safety */
                        break;
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next,
                                           xop->lhc + HAMMER2_DIRHASH_LOMASK,
                                           &cache_index,
                                           HAMMER2_LOOKUP_ALWAYS |
                                           HAMMER2_LOOKUP_SHARED);
        }
done:
        hammer2_xop_feed(&xop->head, NULL, clindex, error);
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
}

/*
 * Generic lookup of a specific key.
 *
 * Used by the inode hidden directory code to find the hidden directory.
 */
void
hammer2_xop_lookup(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_scanlhc_t *xop = &arg->xop_scanlhc;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        int cache_index = -1;   /* XXX */
        int error = 0;

        parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        chain = NULL;
        if (parent == NULL) {
                error = EIO;
                goto done;
        }

        /*
         * Lookup all possibly conflicting directory entries, the feed
         * inherits the chain's lock so do not unlock it on the iteration.
         */
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     xop->lhc, xop->lhc,
                                     &cache_index,
                                     HAMMER2_LOOKUP_ALWAYS |
                                     HAMMER2_LOOKUP_SHARED);
        if (chain)
                hammer2_xop_feed(&xop->head, chain, clindex, chain->error);
        else
                hammer2_xop_feed(&xop->head, NULL, clindex, ENOENT);

done:
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
}

/*
 * Generic scan
 *
 * WARNING! Fed chains must be locked shared so ownership can be transfered
 *          and to prevent frontend/backend stalls that would occur with an
 *          exclusive lock.  The shared lock also allows chain->data to be
 *          retained.
 */
void
hammer2_xop_scanall(hammer2_xop_t *arg, int clindex)
{
        hammer2_xop_scanall_t *xop = &arg->xop_scanall;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        int cache_index = -1;
        int error = 0;

        /*
         * Assert required flags.
         */
        KKASSERT(xop->resolve_flags & HAMMER2_RESOLVE_SHARED);
        KKASSERT(xop->lookup_flags & HAMMER2_LOOKUP_SHARED);

        /*
         * The inode's chain is the iterator.  If we cannot acquire it our
         * contribution ends here.
         */
        parent = hammer2_inode_chain(xop->head.ip1, clindex,
                                     xop->resolve_flags);
        if (parent == NULL) {
                kprintf("xop_readdir: NULL parent\n");
                goto done;
        }

        /*
         * Generic scan of exact records.  Note that indirect blocks are
         * automatically recursed and will not be returned.
         */
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     xop->key_beg, xop->key_end,
                                     &cache_index, xop->lookup_flags);
        while (chain) {
                error = hammer2_xop_feed(&xop->head, chain, clindex, 0);
                if (error)
                        break;
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, xop->key_end,
                                           &cache_index, xop->lookup_flags);
        }
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
        hammer2_chain_unlock(parent);
        hammer2_chain_drop(parent);
done:
        hammer2_xop_feed(&xop->head, NULL, clindex, error);
}