hammer2 - Implement error processing and free reserve enforcement

[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 *oparent, hammer2_chain_t *ochain, int clindex)
{
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        hammer2_key_t inum;
        int error;

        error = 0;
        chain = hammer2_chain_lookup_init(ochain, 0);

        if (chain->bref.type == HAMMER2_BREF_TYPE_DIRENT) {
                if (oparent)
                        hammer2_chain_unlock(oparent);
                inum = chain->bref.embed.dirent.inum;
                parent = NULL;
                error = hammer2_chain_inode_find(chain->pmp, inum,
                                                 clindex, 0,
                                                 &parent, &chain);
                if (parent) {
                        hammer2_chain_unlock(parent);
                        hammer2_chain_drop(parent);
                }
                if (oparent) {
                        hammer2_chain_lock(oparent, HAMMER2_RESOLVE_ALWAYS);
                        if (ochain->parent != oparent) {
                                if (chain) {
                                        hammer2_chain_unlock(chain);
                                        hammer2_chain_drop(chain);
                                }
                                return HAMMER2_ERROR_EAGAIN;
                        }
                }
        }

        /*
         * Determine if the directory is empty or not by checking its
         * visible namespace (the area which contains directory entries).
         */
        parent = chain;
        chain = NULL;
        if (parent) {
                chain = hammer2_chain_lookup(&parent, &key_next,
                                             HAMMER2_DIRHASH_VISIBLE,
                                             HAMMER2_KEY_MAX,
                                             &error, 0);
        }
        if (chain) {
                error = HAMMER2_ERROR_ENOTEMPTY;
                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_thread_t *thr, hammer2_xop_t *arg)
{
        hammer2_xop_ipcluster_t *xop = &arg->xop_ipcluster;
        hammer2_chain_t *chain;
        int error;

        chain = hammer2_inode_chain(xop->head.ip1, thr->clindex,
                                    HAMMER2_RESOLVE_ALWAYS |
                                    HAMMER2_RESOLVE_SHARED);
        if (chain)
                error = chain->error;
        else
                error = HAMMER2_ERROR_EIO;
                
        hammer2_xop_feed(&xop->head, chain, thr->clindex, error);
        if (chain) {
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
}

/*
 * Backend for hammer2_vop_readdir()
 */
void
hammer2_xop_readdir(hammer2_thread_t *thr, hammer2_xop_t *arg)
{
        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 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, thr->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,
                                     &error, HAMMER2_LOOKUP_SHARED);
        if (chain == NULL) {
                chain = hammer2_chain_lookup(&parent, &key_next,
                                             lkey, HAMMER2_KEY_MAX,
                                             &error, HAMMER2_LOOKUP_SHARED);
        }
        while (chain) {
                error = hammer2_xop_feed(&xop->head, chain, thr->clindex, 0);
                if (error)
                        goto break2;
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, HAMMER2_KEY_MAX,
                                           &error, HAMMER2_LOOKUP_SHARED);
        }
break2:
        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, thr->clindex, error);
}

/*
 * Backend for hammer2_vop_nresolve()
 */
void
hammer2_xop_nresolve(hammer2_thread_t *thr, hammer2_xop_t *arg)
{
        hammer2_xop_nresolve_t *xop = &arg->xop_nresolve;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        const char *name;
        size_t name_len;
        hammer2_key_t key_next;
        hammer2_key_t lhc;
        int error;

        parent = hammer2_inode_chain(xop->head.ip1, thr->clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        if (parent == NULL) {
                kprintf("xop_nresolve: NULL parent\n");
                chain = NULL;
                error = HAMMER2_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,
                                     &error,
                                     HAMMER2_LOOKUP_ALWAYS |
                                     HAMMER2_LOOKUP_SHARED);
        while (chain) {
                if (hammer2_chain_dirent_test(chain, name, name_len))
                        break;
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next,
                                           lhc + HAMMER2_DIRHASH_LOMASK,
                                           &error,
                                           HAMMER2_LOOKUP_ALWAYS |
                                           HAMMER2_LOOKUP_SHARED);
        }

        /*
         * If the entry is a hardlink pointer, resolve it.
         */
        if (chain && chain->error == 0) {
                if (chain->bref.type == HAMMER2_BREF_TYPE_DIRENT) {
                        lhc = chain->bref.embed.dirent.inum;
                        error = hammer2_chain_inode_find(chain->pmp,
                                                         lhc,
                                                         thr->clindex,
                                                         HAMMER2_LOOKUP_SHARED,
                                                         &parent,
                                                         &chain);
                }
        } else if (chain && error == 0) {
                error = chain->error;
        }
done:
        error = hammer2_xop_feed(&xop->head, chain, thr->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
 * backend for pfs_delete.
 *
 * This function locates and removes a directory entry, and will lookup
 * and return the underlying inode.  For directory entries the underlying
 * inode is not removed.  If the directory entry is the actual inode itself,
 * it may be conditonally removed and returned.
 *
 * WARNING!  Any target inode's nlinks may not be synchronized to the
 *           in-memory inode.  The frontend's hammer2_inode_unlink_finisher()
 *           is responsible for the final disposition of the actual inode.
 */
void
hammer2_xop_unlink(hammer2_thread_t *thr, hammer2_xop_t *arg)
{
        hammer2_xop_unlink_t *xop = &arg->xop_unlink;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        const char *name;
        size_t name_len;
        hammer2_key_t key_next;
        hammer2_key_t lhc;
        int error;

again:
        /*
         * Requires exclusive lock
         */
        parent = hammer2_inode_chain(xop->head.ip1, thr->clindex,
                                     HAMMER2_RESOLVE_ALWAYS);
        chain = NULL;
        if (parent == NULL) {
                kprintf("xop_nresolve: NULL parent\n");
                error = HAMMER2_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,
                                     &error, HAMMER2_LOOKUP_ALWAYS);
        while (chain) {
                if (hammer2_chain_dirent_test(chain, name, name_len))
                        break;
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next,
                                           lhc + HAMMER2_DIRHASH_LOMASK,
                                           &error, HAMMER2_LOOKUP_ALWAYS);
        }

        /*
         * The directory entry will either be a BREF_TYPE_DIRENT or a
         * BREF_TYPE_INODE.  We always permanently delete DIRENTs, but
         * must go by xop->dopermanent for BREF_TYPE_INODE.
         *
         * Note that the target chain's nlinks may not be synchronized with
         * the in-memory hammer2_inode_t structure, so we don't try to do
         * anything fancy here.  The frontend deals with nlinks
         * synchronization.
         */
        if (chain && chain->error == 0) {
                int dopermanent = xop->dopermanent & 1;
                int doforce = xop->dopermanent & 2;
                uint8_t type;

                /*
                 * If the directory entry is the actual inode then use its
                 * type for the directory typing tests, otherwise if it is
                 * a directory entry, pull the type field from the entry.
                 *
                 * Directory entries are always permanently deleted
                 * (because they aren't the actual inode).
                 */
                if (chain->bref.type == HAMMER2_BREF_TYPE_DIRENT) {
                        type = chain->bref.embed.dirent.type;
                        dopermanent |= HAMMER2_DELETE_PERMANENT;
                } else {
                        type = chain->data->ipdata.meta.type;
                }

                /*
                 * Check directory typing and delete the entry.  Note that
                 * nlinks adjustments are made on the real inode by the
                 * frontend, not here.
                 *
                 * Unfortunately, checkdirempty() may have to unlock (parent).
                 * If it no longer matches chain->parent after re-locking,
                 * EAGAIN is returned.
                 */
                if (type == HAMMER2_OBJTYPE_DIRECTORY && doforce) {
                        /*
                         * If doforce then execute the operation even if
                         * the directory is not empty or errored.
                         */
                        /* ignore chain->error */
                        error = hammer2_chain_delete(parent, chain,
                                             xop->head.mtid, dopermanent);
                } else if (type == HAMMER2_OBJTYPE_DIRECTORY &&
                           (error = checkdirempty(parent, chain, thr->clindex)) != 0) {
                        /*
                         * error may be EAGAIN or ENOTEMPTY
                         */
                        if (error == HAMMER2_ERROR_EAGAIN) {
                                hammer2_chain_unlock(chain);
                                hammer2_chain_drop(chain);
                                hammer2_chain_unlock(parent);
                                hammer2_chain_drop(parent);
                                goto again;
                        }
                } else if (type == HAMMER2_OBJTYPE_DIRECTORY &&
                    xop->isdir == 0) {
                        error = HAMMER2_ERROR_ENOTDIR;
                } else if (type != HAMMER2_OBJTYPE_DIRECTORY &&
                           xop->isdir >= 1) {
                        error = HAMMER2_ERROR_EISDIR;
                } else {
                        /*
                         * Delete the directory entry.  chain might also
                         * be a directly-embedded inode.
                         */
                        error = chain->error;
                        hammer2_chain_delete(parent, chain,
                                             xop->head.mtid, dopermanent);
                }
        } else {
                if (chain && error == 0)
                        error = chain->error;
        }

        /*
         * If chain is a directory entry we must resolve it.  We do not try
         * to manipulate the contents as it might not be synchronized with
         * the frontend hammer2_inode_t, nor do we try to lookup the
         * frontend hammer2_inode_t here (we are the backend!).
         */
        if (chain && chain->bref.type == HAMMER2_BREF_TYPE_DIRENT) {
                int error2;

                lhc = chain->bref.embed.dirent.inum;

                error2 = hammer2_chain_inode_find(chain->pmp, lhc,
                                                  thr->clindex, 0,
                                                  &parent, &chain);
                if (error2) {
                        kprintf("inode_find: %016jx %p failed\n",
                                lhc, chain);
                        error2 = 0;     /* silently ignore */
                }
                if (error == 0)
                        error = error2;
        }

        /*
         * Return the inode target for further action.  Typically used by
         * hammer2_inode_unlink_finisher().
         */
done:
        hammer2_xop_feed(&xop->head, chain, thr->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;
        }
}

/*
 * Backend for hammer2_vop_nrename()
 *
 * This handles the backend rename operation.  Typically this renames
 * directory entries but can also be used to rename embedded inodes.
 *
 * NOTE! The frontend is responsible for updating the inode meta-data in
 *       the file being renamed and for decrementing the target-replaced
 *       inode's nlinks, if present.
 */
void
hammer2_xop_nrename(hammer2_thread_t *thr, hammer2_xop_t *arg)
{
        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_next;
        int error;

        /*
         * We need the precise parent chain to issue the deletion.
         *
         * If this is a directory entry we must locate the underlying
         * inode.  If it is an embedded inode we can act directly on it.
         */
        ip = xop->head.ip2;
        pmp = ip->pmp;
        chain = NULL;
        error = 0;

        if (xop->ip_key & HAMMER2_DIRHASH_VISIBLE) {
                /*
                 * Find ip's direct parent chain.
                 */
                chain = hammer2_inode_chain(ip, thr->clindex,
                                            HAMMER2_RESOLVE_ALWAYS);
                if (chain == NULL) {
                        error = HAMMER2_ERROR_EIO;
                        parent = NULL;
                        goto done;
                }
                parent = hammer2_chain_getparent(chain, HAMMER2_RESOLVE_ALWAYS);
                if (parent == NULL) {
                        error = HAMMER2_ERROR_EIO;
                        goto done;
                }
        } else {
                /*
                 * The directory entry for the head.ip1 inode
                 * is in fdip, do a namespace search.
                 */
                hammer2_key_t lhc;
                const char *name;
                size_t name_len;

                parent = hammer2_inode_chain(xop->head.ip1, thr->clindex,
                                             HAMMER2_RESOLVE_ALWAYS);
                if (parent == NULL) {
                        kprintf("xop_nrename: NULL parent\n");
                        error = HAMMER2_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,
                                             &error, HAMMER2_LOOKUP_ALWAYS);
                while (chain) {
                        if (hammer2_chain_dirent_test(chain, name, name_len))
                                break;
                        chain = hammer2_chain_next(&parent, chain, &key_next,
                                                   key_next,
                                                   lhc + HAMMER2_DIRHASH_LOMASK,
                                                   &error,
                                                   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);
                if (error == 0)
                        error = HAMMER2_ERROR_ENOENT;
                goto done;
        }

        if (chain->error) {
                error = chain->error;
                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 */

        /*
         * Adjust fields in the deleted chain appropriate for the rename
         * operation.
         *
         * NOTE! For embedded inodes, the frontend will officially replicate
         *       the field adjustments, but we also do it here to maintain
         *       consistency in case of a crash.
         */
        if (chain->bref.key != xop->lhc ||
            xop->head.name1_len != xop->head.name2_len ||
            bcmp(xop->head.name1, xop->head.name2, xop->head.name1_len) != 0) {
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE) {
                        hammer2_inode_data_t *wipdata;

                        error = hammer2_chain_modify(chain, xop->head.mtid,
                                                     0, 0);
                        if (error == 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;
                        }
                }
                if (chain->bref.type == HAMMER2_BREF_TYPE_DIRENT) {
                        if (xop->head.name2_len <=
                            sizeof(chain->bref.check.buf)) {
                                /*
                                 * Remove any related data buffer, we can
                                 * embed the filename in the bref itself.
                                 */
                                error = hammer2_chain_resize(
                                                chain, xop->head.mtid, 0, 0, 0);
                                if (error == 0) {
                                        error = hammer2_chain_modify(
                                                        chain, xop->head.mtid,
                                                        0, 0);
                                }
                                if (error == 0) {
                                        bzero(chain->bref.check.buf,
                                              sizeof(chain->bref.check.buf));
                                        bcopy(xop->head.name2,
                                              chain->bref.check.buf,
                                              xop->head.name2_len);
                                }
                        } else {
                                /*
                                 * Associate a data buffer with the bref.
                                 * Zero it for consistency.  Note that the
                                 * data buffer is not 64KB so use chain->bytes
                                 * instead of sizeof().
                                 */
                                error = hammer2_chain_resize(
                                        chain, xop->head.mtid, 0,
                                        hammer2_getradix(HAMMER2_ALLOC_MIN), 0);
                                if (error == 0) {
                                        error = hammer2_chain_modify(
                                                    chain, xop->head.mtid,
                                                    0, 0);
                                }
                                if (error == 0) {
                                        bzero(chain->data->buf, chain->bytes);
                                        bcopy(xop->head.name2,
                                              chain->data->buf,
                                              xop->head.name2_len);
                                }
                        }
                        if (error == 0) {
                                chain->bref.embed.dirent.namlen =
                                        xop->head.name2_len;
                        }
                }
        }

        /*
         * The frontend will replicate this operation and is the real final
         * authority, but adjust the inode's iparent field too if the inode
         * is embedded in the directory.
         */
        if (chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
            chain->data->ipdata.meta.iparent != xop->head.ip3->meta.inum) {
                hammer2_inode_data_t *wipdata;

                error = hammer2_chain_modify(chain, xop->head.mtid, 0, 0);
                if (error == 0) {
                        wipdata = &chain->data->ipdata;
                        wipdata->meta.iparent = xop->head.ip3->meta.inum;
                }
        }

        /*
         * Destroy any matching target(s) before creating the new entry.
         * This will result in some ping-ponging of the directory key
         * iterator but that is ok.
         */
        parent = hammer2_inode_chain(xop->head.ip3, thr->clindex,
                                     HAMMER2_RESOLVE_ALWAYS);
        if (parent == NULL) {
                error = HAMMER2_ERROR_EIO;
                goto done;
        }

        if (error == 0) {
                tmp = hammer2_chain_lookup(&parent, &key_next,
                                           xop->lhc & ~HAMMER2_DIRHASH_LOMASK,
                                           xop->lhc | HAMMER2_DIRHASH_LOMASK,
                                           &error,
                                           HAMMER2_LOOKUP_ALWAYS);
                while (tmp) {
                        if (hammer2_chain_dirent_test(tmp, xop->head.name2,
                                                      xop->head.name2_len)) {
                                hammer2_chain_delete(parent, tmp,
                                                     xop->head.mtid, 0);
                        }
                        tmp = hammer2_chain_next(&parent, tmp, &key_next,
                                                 key_next,
                                                 xop->lhc |
                                                  HAMMER2_DIRHASH_LOMASK,
                                                 &error,
                                                 HAMMER2_LOOKUP_ALWAYS);
                }
        }
        if (error == 0) {
                /*
                 * A relookup is required before the create to properly
                 * position the parent chain.
                 */
                tmp = hammer2_chain_lookup(&parent, &key_next,
                                           xop->lhc, xop->lhc,
                                           &error, 0);
                KKASSERT(tmp == NULL);
                error = hammer2_chain_create(&parent, &chain,
                                             pmp, HAMMER2_METH_DEFAULT,
                                             xop->lhc, 0,
                                             HAMMER2_BREF_TYPE_INODE,
                                             HAMMER2_INODE_BYTES,
                                             xop->head.mtid, 0, 0);
        }
done:
        hammer2_xop_feed(&xop->head, NULL, thr->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_thread_t *thr, hammer2_xop_t *arg)
{
        hammer2_xop_scanlhc_t *xop = &arg->xop_scanlhc;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        int error = 0;

        parent = hammer2_inode_chain(xop->head.ip1, thr->clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        if (parent == NULL) {
                kprintf("xop_nresolve: NULL parent\n");
                chain = NULL;
                error = HAMMER2_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,
                                     &error,
                                     HAMMER2_LOOKUP_ALWAYS |
                                     HAMMER2_LOOKUP_SHARED);
        while (chain) {
                error = hammer2_xop_feed(&xop->head, chain, thr->clindex, 0);
                if (error) {
                        hammer2_chain_unlock(chain);
                        hammer2_chain_drop(chain);
                        chain = NULL;   /* safety */
                        goto done;
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next,
                                           xop->lhc + HAMMER2_DIRHASH_LOMASK,
                                           &error,
                                           HAMMER2_LOOKUP_ALWAYS |
                                           HAMMER2_LOOKUP_SHARED);
        }
done:
        hammer2_xop_feed(&xop->head, NULL, thr->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_thread_t *thr, hammer2_xop_t *arg)
{
        hammer2_xop_scanlhc_t *xop = &arg->xop_scanlhc;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        int error = 0;

        parent = hammer2_inode_chain(xop->head.ip1, thr->clindex,
                                     HAMMER2_RESOLVE_ALWAYS |
                                     HAMMER2_RESOLVE_SHARED);
        chain = NULL;
        if (parent == NULL) {
                error = HAMMER2_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,
                                     &error,
                                     HAMMER2_LOOKUP_ALWAYS |
                                     HAMMER2_LOOKUP_SHARED);
        if (error == 0) {
                if (chain)
                        error = chain->error;
                else
                        error = HAMMER2_ERROR_ENOENT;
        }
        hammer2_xop_feed(&xop->head, chain, thr->clindex, error);

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_thread_t *thr, hammer2_xop_t *arg)
{
        hammer2_xop_scanall_t *xop = &arg->xop_scanall;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        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, thr->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,
                                     &error, xop->lookup_flags);
        while (chain) {
                error = hammer2_xop_feed(&xop->head, chain, thr->clindex, 0);
                if (error)
                        goto break2;
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, xop->key_end,
                                           &error, xop->lookup_flags);
        }
break2:
        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, thr->clindex, error);
}