xnu-2422.115.4.tar.gz

[apple/xnu.git] / bsd / hfs / hfs_chash.c

diff --git a/bsd/hfs/hfs_chash.c b/bsd/hfs/hfs_chash.c
index eb2204aa830ece7ff8b8210dd851d543ccc23dcd..b162a53b2cd502f53e3f615ba168a3988eef6793 100644 (file)
--- a/bsd/hfs/hfs_chash.c
+++ b/bsd/hfs/hfs_chash.c
@@ -1,16 +1,19 @@
 /*
 /*

- * Copyright (c) 2002 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2002-2012 Apple Inc. All rights reserved.

  *
  *

- * @APPLE_LICENSE_HEADER_START@
- * 
- * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@

  * 
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
  * 
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in

- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ * 
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.

  * 
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * 
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER


@@ -20,7 +23,7 @@
  * Please see the License for the specific language governing rights and
  * limitations under the License.
  * 
  * Please see the License for the specific language governing rights and
  * limitations under the License.
  * 

- * @APPLE_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@

  */
 
 /*
  */
 
 /*


@@ -62,20 +65,26 @@
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/vnode.h>
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/vnode.h>

+#include <sys/kernel.h>

 #include <sys/malloc.h>
 #include <sys/proc.h>
 #include <sys/queue.h>
 
 #include <sys/malloc.h>
 #include <sys/proc.h>
 #include <sys/queue.h>
 

+
+#include "hfs.h"       /* XXX bringup */

 #include "hfs_cnode.h"
 
 #include "hfs_cnode.h"
 

+extern lck_attr_t *  hfs_lock_attr;
+extern lck_grp_t *  hfs_mutex_group;
+extern lck_grp_t *  hfs_rwlock_group;
+
+lck_grp_t * chash_lck_grp;
+lck_grp_attr_t * chash_lck_grp_attr;
+lck_attr_t * chash_lck_attr;
+
+
+#define CNODEHASH(hfsmp, inum) (&hfsmp->hfs_cnodehashtbl[(inum) & hfsmp->hfs_cnodehash])

 
 

-/*
- * Structures associated with cnode caching.
- */
-LIST_HEAD(cnodehashhead, cnode) *cnodehashtbl;
-u_long cnodehash;              /* size of hash table - 1 */
-#define CNODEHASH(device, inum) (&cnodehashtbl[((device) + (inum)) & cnodehash])
-struct slock hfs_chash_slock;

 
 /*
  * Initialize cnode hash table.
 
 /*
  * Initialize cnode hash table.


@@ -84,8 +93,47 @@ __private_extern__
 void
 hfs_chashinit()
 {
 void
 hfs_chashinit()
 {

-       cnodehashtbl = hashinit(desiredvnodes, M_HFSMNT, &cnodehash);
-       simple_lock_init(&hfs_chash_slock);
+       chash_lck_grp_attr= lck_grp_attr_alloc_init();
+       chash_lck_grp  = lck_grp_alloc_init("cnode_hash", chash_lck_grp_attr);
+       chash_lck_attr = lck_attr_alloc_init();
+}
+
+static void hfs_chash_lock(struct hfsmount *hfsmp) 
+{
+       lck_mtx_lock(&hfsmp->hfs_chash_mutex);
+}
+
+static void hfs_chash_lock_spin(struct hfsmount *hfsmp) 
+{
+       lck_mtx_lock_spin(&hfsmp->hfs_chash_mutex);
+}
+
+static void hfs_chash_lock_convert (__unused struct hfsmount *hfsmp)
+{
+       lck_mtx_convert_spin(&hfsmp->hfs_chash_mutex);
+}
+
+static void hfs_chash_unlock(struct hfsmount *hfsmp) 
+{
+       lck_mtx_unlock(&hfsmp->hfs_chash_mutex);
+}
+
+__private_extern__
+void
+hfs_chashinit_finish(struct hfsmount *hfsmp)
+{
+       lck_mtx_init(&hfsmp->hfs_chash_mutex, chash_lck_grp, chash_lck_attr);
+
+       hfsmp->hfs_cnodehashtbl = hashinit(desiredvnodes / 4, M_HFSMNT, &hfsmp->hfs_cnodehash);
+}
+
+__private_extern__
+void
+hfs_delete_chash(struct hfsmount *hfsmp)
+{
+       lck_mtx_destroy(&hfsmp->hfs_chash_mutex, chash_lck_grp);
+
+       FREE(hfsmp->hfs_cnodehashtbl, M_HFSMNT);

 }
 
 
 }
 
 


@@ -93,123 +141,326 @@ hfs_chashinit()
  * Use the device, inum pair to find the incore cnode.
  *
  * If it is in core, but locked, wait for it.
  * Use the device, inum pair to find the incore cnode.
  *
  * If it is in core, but locked, wait for it.

- *
- * If the requested vnode (fork) is not available, then
- * take a reference on the other vnode (fork) so that
- * the upcoming getnewvnode can not aquire it.

  */
  */

-__private_extern__
-struct cnode *
-hfs_chashget(dev_t dev, ino_t inum, int wantrsrc,
-               struct vnode **vpp, struct vnode **rvpp)
+struct vnode *
+hfs_chash_getvnode(struct hfsmount *hfsmp, ino_t inum, int wantrsrc, int skiplock, int allow_deleted)

 {
 {

-       struct proc *p = current_proc();

        struct cnode *cp;
        struct vnode *vp;
        int error;
        struct cnode *cp;
        struct vnode *vp;
        int error;

+       u_int32_t vid;

 
 

-       *vpp = NULLVP;
-       *rvpp = NULLVP;

        /* 
         * Go through the hash list
         * If a cnode is in the process of being cleaned out or being
         * allocated, wait for it to be finished and then try again.
         */
 loop:
        /* 
         * Go through the hash list
         * If a cnode is in the process of being cleaned out or being
         * allocated, wait for it to be finished and then try again.
         */
 loop:

-       simple_lock(&hfs_chash_slock);
-       for (cp = CNODEHASH(dev, inum)->lh_first; cp; cp = cp->c_hash.le_next) {
-               if ((cp->c_fileid != inum) || (cp->c_dev != dev))
+       hfs_chash_lock_spin(hfsmp);
+
+       for (cp = CNODEHASH(hfsmp, inum)->lh_first; cp; cp = cp->c_hash.le_next) {
+               if (cp->c_fileid != inum)

                        continue;
                        continue;

-               if (ISSET(cp->c_flag, C_ALLOC)) {
-                       /*
-                        * cnode is being created. Wait for it to finish.
-                        */
-                       SET(cp->c_flag, C_WALLOC);
-                       simple_unlock(&hfs_chash_slock);
-                       (void) tsleep((caddr_t)cp, PINOD, "hfs_chashget-1", 0);
+               /* Wait if cnode is being created or reclaimed. */
+               if (ISSET(cp->c_hflag, H_ALLOC | H_TRANSIT | H_ATTACH)) {
+                       SET(cp->c_hflag, H_WAITING);
+
+                       (void) msleep(cp, &hfsmp->hfs_chash_mutex, PDROP | PINOD,
+                                     "hfs_chash_getvnode", 0);

                        goto loop;
                        goto loop;

-               }       
-               if (ISSET(cp->c_flag, C_TRANSIT)) {
-                       /*
-                        * cnode is getting reclaimed wait for
-                        * the operation to complete and return
-                        * error
+               }
+               /* Obtain the desired vnode. */
+               vp = wantrsrc ? cp->c_rsrc_vp : cp->c_vp;
+               if (vp == NULLVP)
+                       goto exit;
+
+               vid = vnode_vid(vp);
+               hfs_chash_unlock(hfsmp);
+
+               if ((error = vnode_getwithvid(vp, vid))) {
+                       /*
+                        * If vnode is being reclaimed, or has
+                        * already changed identity, no need to wait

                         */
                         */

-                       SET(cp->c_flag, C_WTRANSIT);
-                       simple_unlock(&hfs_chash_slock);
-                       (void)tsleep((caddr_t)cp, PINOD, "hfs_chashget-2", 0);
-                       goto loop;
+                       return (NULL);
+               }
+               if (!skiplock && hfs_lock(cp, HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
+                       vnode_put(vp);
+                       return (NULL);
+               }
+
+               /*
+                * Skip cnodes that are not in the name space anymore
+                * we need to check with the cnode lock held because
+                * we may have blocked acquiring the vnode ref or the
+                * lock on the cnode which would allow the node to be
+                * unlinked
+                */
+               if (!allow_deleted) {
+                       if (cp->c_flag & (C_NOEXISTS | C_DELETED)) {
+                               if (!skiplock) {
+                                       hfs_unlock(cp);
+                               }
+                               vnode_put(vp);
+                               return (NULL);
+                       }                       

                }
                }

-               if (cp->c_flag & (C_NOEXISTS | C_DELETED))
+               return (vp);
+       }
+exit:
+       hfs_chash_unlock(hfsmp);
+       return (NULL);
+}
+
+
+/*
+ * Use the device, fileid pair to snoop an incore cnode.
+ *
+ * A cnode can exists in chash even after it has been 
+ * deleted from the catalog, so this function returns 
+ * ENOENT if C_NOEXIST is set in the cnode's flag.
+ * 
+ */
+int
+hfs_chash_snoop(struct hfsmount *hfsmp, ino_t inum, int existence_only, int (*callout)(const struct cat_desc *,
+                const struct cat_attr *, void *), void * arg)
+{
+       struct cnode *cp;
+       int result = ENOENT;
+
+       /* 
+        * Go through the hash list
+        * If a cnode is in the process of being cleaned out or being
+        * allocated, wait for it to be finished and then try again.
+        */
+       hfs_chash_lock(hfsmp);
+
+       for (cp = CNODEHASH(hfsmp, inum)->lh_first; cp; cp = cp->c_hash.le_next) {
+               if (cp->c_fileid != inum)

                        continue;
                        continue;

+       
+               /*
+                * Under normal circumstances, we would want to return ENOENT if a cnode is in
+                * the hash and it is marked C_NOEXISTS or C_DELETED.  However, if the CNID
+                * namespace has wrapped around, then we have the possibility of collisions.  
+                * In that case, we may use this function to validate whether or not we 
+                * should trust the nextCNID value in the hfs mount point.  
+                * 
+                * If we didn't do this, then it would be possible for a cnode that is no longer backed
+                * by anything on-disk (C_NOEXISTS) to still exist in the hash along with its
+                * vnode.  The cat_create routine could then create a new entry in the catalog
+                * re-using that CNID.  Then subsequent hfs_getnewvnode calls will repeatedly fail
+                * trying to look it up/validate it because it is marked C_NOEXISTS.  So we want
+                * to prevent that from happening as much as possible.
+                */
+               if (existence_only) {
+                       result = 0;
+                       break;
+               }
+
+               /* Skip cnodes that have been removed from the catalog */
+               if (cp->c_flag & (C_NOEXISTS | C_DELETED)) {
+                       break;
+               }
+               /* Skip cnodes being created or reclaimed. */
+               if (!ISSET(cp->c_hflag, H_ALLOC | H_TRANSIT | H_ATTACH)) {
+                       result = callout(&cp->c_desc, &cp->c_attr, arg);
+               }
+               break;
+       }
+       hfs_chash_unlock(hfsmp);
+
+       return (result);
+}
+
+
+/*
+ * Use the device, fileid pair to find the incore cnode.
+ * If no cnode if found one is created
+ *
+ * If it is in core, but locked, wait for it.
+ *
+ * If the cnode is C_DELETED, then return NULL since that 
+ * inum is no longer valid for lookups (open-unlinked file).
+ *
+ * If the cnode is C_DELETED but also marked C_RENAMED, then that means
+ * the cnode was renamed over and a new entry exists in its place.  The caller
+ * should re-drive the lookup to get the newer entry.  In that case, we'll still
+ * return NULL for the cnode, but also return GNV_CHASH_RENAMED in the output flags
+ * of this function to indicate the caller that they should re-drive.
+ */
+struct cnode *
+hfs_chash_getcnode(struct hfsmount *hfsmp, ino_t inum, struct vnode **vpp, 
+                                  int wantrsrc, int skiplock, int *out_flags, int *hflags)
+{
+       struct cnode    *cp;
+       struct cnode    *ncp = NULL;
+       vnode_t         vp;
+       u_int32_t       vid;
+
+       /* 
+        * Go through the hash list
+        * If a cnode is in the process of being cleaned out or being
+        * allocated, wait for it to be finished and then try again.
+        */
+loop:
+       hfs_chash_lock_spin(hfsmp);

 
 

+loop_with_lock:
+       for (cp = CNODEHASH(hfsmp, inum)->lh_first; cp; cp = cp->c_hash.le_next) {
+               if (cp->c_fileid != inum)
+                       continue;

                /*
                /*

-                * Try getting the desired vnode first.  If
-                * it isn't available then take a reference
-                * on the other vnode.
+                * Wait if cnode is being created, attached to or reclaimed.

                 */
                 */

+               if (ISSET(cp->c_hflag, H_ALLOC | H_ATTACH | H_TRANSIT)) {
+                       SET(cp->c_hflag, H_WAITING);
+
+                       (void) msleep(cp, &hfsmp->hfs_chash_mutex, PINOD,
+                                     "hfs_chash_getcnode", 0);
+                       goto loop_with_lock;
+               }

                vp = wantrsrc ? cp->c_rsrc_vp : cp->c_vp;
                vp = wantrsrc ? cp->c_rsrc_vp : cp->c_vp;

-               if (vp == NULLVP)
-                       vp = wantrsrc ? cp->c_vp : cp->c_rsrc_vp;
-               if (vp == NULLVP)
-                       panic("hfs_chashget: orphaned cnode in hash");
+               if (vp == NULL) {
+                       /*
+                        * The desired vnode isn't there so tag the cnode.
+                        */
+                       SET(cp->c_hflag, H_ATTACH);
+                       *hflags |= H_ATTACH;

 
 

-               simple_lock(&vp->v_interlock);
-               simple_unlock(&hfs_chash_slock);
-               if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, p))
-                       goto loop;
-               else if (cp->c_flag & C_NOEXISTS) {
+                       hfs_chash_unlock(hfsmp);
+               } else {
+                       vid = vnode_vid(vp);
+
+                       hfs_chash_unlock(hfsmp);
+
+                       if (vnode_getwithvid(vp, vid))
+                               goto loop;
+               }
+               if (ncp) {

                        /*
                        /*

-                        * While we were blocked the cnode got deleted.
+                        * someone else won the race to create
+                        * this cnode and add it to the hash
+                        * just dump our allocation

                         */
                         */

-                       vput(vp);
-                       goto loop;
+                       FREE_ZONE(ncp, sizeof(struct cnode), M_HFSNODE);
+                       ncp = NULL;
+               }
+
+               if (!skiplock) {
+                       hfs_lock(cp, HFS_EXCLUSIVE_LOCK, HFS_LOCK_ALLOW_NOEXISTS);

                }
 
                }
 

-               if (VNODE_IS_RSRC(vp))
-                       *rvpp = vp;
-               else
-                       *vpp = vp;

                /*
                /*

-                * Note that vget can block before aquiring the
-                * cnode lock.  So we need to check if the vnode
-                * we wanted was created while we blocked.
+                * Skip cnodes that are not in the name space anymore
+                * we need to check with the cnode lock held because
+                * we may have blocked acquiring the vnode ref or the
+                * lock on the cnode which would allow the node to be
+                * unlinked.
+                *
+                * Don't return a cnode in this case since the inum
+                * is no longer valid for lookups.

                 */
                 */

-               if (wantrsrc && *rvpp == NULL && cp->c_rsrc_vp) {
-                       error = vget(cp->c_rsrc_vp, 0, p);
-                       vput(*vpp);     /* ref no longer needed */
-                       *vpp = NULL;
-                       if (error)
-                               goto loop;
-                       *rvpp = cp->c_rsrc_vp;
-
-               } else if (!wantrsrc && *vpp == NULL && cp->c_vp) {
-                       error = vget(cp->c_vp, 0, p);
-                       vput(*rvpp);    /* ref no longer needed */
-                       *rvpp = NULL;
-                       if (error)
-                               goto loop;
-                       *vpp = cp->c_vp;
+               if ((cp->c_flag & (C_NOEXISTS | C_DELETED)) && !wantrsrc) {
+                       int renamed = 0;
+                       if (cp->c_flag & C_RENAMED) {
+                               renamed = 1;
+                       }
+                       if (!skiplock)
+                               hfs_unlock(cp);
+                       if (vp != NULLVP) {
+                               vnode_put(vp);
+                       } else {
+                               hfs_chash_lock_spin(hfsmp);
+                               CLR(cp->c_hflag, H_ATTACH);
+                               *hflags &= ~H_ATTACH;
+                               if (ISSET(cp->c_hflag, H_WAITING)) {
+                                       CLR(cp->c_hflag, H_WAITING);
+                                       wakeup((caddr_t)cp);
+                               }
+                               hfs_chash_unlock(hfsmp);
+                       }
+                       vp = NULL;
+                       cp = NULL;
+                       if (renamed) {
+                               *out_flags = GNV_CHASH_RENAMED;
+                       }

                }
                }

+               *vpp = vp;

                return (cp);
        }
                return (cp);
        }

-       simple_unlock(&hfs_chash_slock);
-       return (NULL);
+
+       /* 
+        * Allocate a new cnode
+        */
+       if (skiplock && !wantrsrc)
+               panic("%s - should never get here when skiplock is set \n", __FUNCTION__);
+
+       if (ncp == NULL) {
+               hfs_chash_unlock(hfsmp);
+
+               MALLOC_ZONE(ncp, struct cnode *, sizeof(struct cnode), M_HFSNODE, M_WAITOK);
+               /*
+                * since we dropped the chash lock, 
+                * we need to go back and re-verify
+                * that this node hasn't come into 
+                * existence...
+                */
+               goto loop;
+       }
+       hfs_chash_lock_convert(hfsmp);
+
+       bzero(ncp, sizeof(struct cnode));
+       SET(ncp->c_hflag, H_ALLOC);
+       *hflags |= H_ALLOC;
+       ncp->c_fileid = inum;
+       TAILQ_INIT(&ncp->c_hintlist); /* make the list empty */
+       TAILQ_INIT(&ncp->c_originlist);
+
+       lck_rw_init(&ncp->c_rwlock, hfs_rwlock_group, hfs_lock_attr);
+       if (!skiplock)
+               (void) hfs_lock(ncp, HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT);
+
+       /* Insert the new cnode with it's H_ALLOC flag set */
+       LIST_INSERT_HEAD(CNODEHASH(hfsmp, inum), ncp, c_hash);
+       hfs_chash_unlock(hfsmp);
+
+       *vpp = NULL;
+       return (ncp);
+}
+
+
+__private_extern__
+void
+hfs_chashwakeup(struct hfsmount *hfsmp, struct cnode *cp, int hflags)
+{
+       hfs_chash_lock_spin(hfsmp);
+
+       CLR(cp->c_hflag, hflags);
+
+       if (ISSET(cp->c_hflag, H_WAITING)) {
+               CLR(cp->c_hflag, H_WAITING);
+               wakeup((caddr_t)cp);
+       }
+       hfs_chash_unlock(hfsmp);

 }
 
 
 /*
 }
 
 
 /*

- * Insert a cnode into the hash table.
+ * Re-hash two cnodes in the hash table.

  */
 __private_extern__
 void
  */
 __private_extern__
 void

-hfs_chashinsert(struct cnode *cp)
+hfs_chash_rehash(struct hfsmount *hfsmp, struct cnode *cp1, struct cnode *cp2)

 {
 {

-       if (cp->c_fileid == 0)
-               panic("hfs_chashinsert: trying to insert file id 0");
-       simple_lock(&hfs_chash_slock);
-       LIST_INSERT_HEAD(CNODEHASH(cp->c_dev, cp->c_fileid), cp, c_hash);
-       simple_unlock(&hfs_chash_slock);
+       hfs_chash_lock_spin(hfsmp);
+
+       LIST_REMOVE(cp1, c_hash);
+       LIST_REMOVE(cp2, c_hash);
+       LIST_INSERT_HEAD(CNODEHASH(hfsmp, cp1->c_fileid), cp1, c_hash);
+       LIST_INSERT_HEAD(CNODEHASH(hfsmp, cp2->c_fileid), cp2, c_hash);
+
+       hfs_chash_unlock(hfsmp);

 }
 
 
 }
 
 


@@ -217,13 +468,116 @@ hfs_chashinsert(struct cnode *cp)
  * Remove a cnode from the hash table.
  */
 __private_extern__
  * Remove a cnode from the hash table.
  */
 __private_extern__

+int
+hfs_chashremove(struct hfsmount *hfsmp, struct cnode *cp)
+{
+       hfs_chash_lock_spin(hfsmp);
+
+       /* Check if a vnode is getting attached */
+       if (ISSET(cp->c_hflag, H_ATTACH)) {
+               hfs_chash_unlock(hfsmp);
+               return (EBUSY);
+       }
+       if (cp->c_hash.le_next || cp->c_hash.le_prev) {
+           LIST_REMOVE(cp, c_hash);
+           cp->c_hash.le_next = NULL;
+           cp->c_hash.le_prev = NULL;
+       }
+       hfs_chash_unlock(hfsmp);
+
+       return (0);
+}
+
+/*
+ * Remove a cnode from the hash table and wakeup any waiters.
+ */
+__private_extern__

 void
 void

-hfs_chashremove(struct cnode *cp)
+hfs_chash_abort(struct hfsmount *hfsmp, struct cnode *cp)

 {
 {

-       simple_lock(&hfs_chash_slock);
+       hfs_chash_lock_spin(hfsmp);
+

        LIST_REMOVE(cp, c_hash);
        cp->c_hash.le_next = NULL;
        cp->c_hash.le_prev = NULL;
        LIST_REMOVE(cp, c_hash);
        cp->c_hash.le_next = NULL;
        cp->c_hash.le_prev = NULL;

-       simple_unlock(&hfs_chash_slock);
+
+       CLR(cp->c_hflag, H_ATTACH | H_ALLOC);
+       if (ISSET(cp->c_hflag, H_WAITING)) {
+               CLR(cp->c_hflag, H_WAITING);
+               wakeup((caddr_t)cp);
+       }
+       hfs_chash_unlock(hfsmp);
+}
+
+
+/*
+ * mark a cnode as in transition
+ */
+__private_extern__
+void
+hfs_chash_mark_in_transit(struct hfsmount *hfsmp, struct cnode *cp)
+{
+       hfs_chash_lock_spin(hfsmp);
+
+        SET(cp->c_hflag, H_TRANSIT);
+
+       hfs_chash_unlock(hfsmp);

 }
 
 }
 

+/* Search a cnode in the hash.  This function does not return cnode which 
+ * are getting created, destroyed or in transition.  Note that this function
+ * does not acquire the cnode hash mutex, and expects the caller to acquire it.
+ * On success, returns pointer to the cnode found.  On failure, returns NULL.
+ */
+static 
+struct cnode *
+hfs_chash_search_cnid(struct hfsmount *hfsmp, cnid_t cnid) 
+{
+       struct cnode *cp;
+
+       for (cp = CNODEHASH(hfsmp, cnid)->lh_first; cp; cp = cp->c_hash.le_next) {
+               if (cp->c_fileid == cnid) {
+                       break;
+               }
+       }
+
+       /* If cnode is being created or reclaimed, return error. */
+       if (cp && ISSET(cp->c_hflag, H_ALLOC | H_TRANSIT | H_ATTACH)) {
+               cp = NULL;
+       }
+
+       return cp;
+}
+
+/* Search a cnode corresponding to given device and ID in the hash.  If the 
+ * found cnode has kHFSHasChildLinkBit cleared, set it.  If the cnode is not 
+ * found, no new cnode is created and error is returned.
+ * 
+ * Return values - 
+ *     -1 : The cnode was not found.
+ *      0 : The cnode was found, and the kHFSHasChildLinkBit was already set.
+ *      1 : The cnode was found, the kHFSHasChildLinkBit was not set, and the 
+ *          function had to set that bit.
+ */
+__private_extern__ 
+int
+hfs_chash_set_childlinkbit(struct hfsmount *hfsmp, cnid_t cnid)
+{
+       int retval = -1;
+       struct cnode *cp;
+
+       hfs_chash_lock_spin(hfsmp);
+
+       cp = hfs_chash_search_cnid(hfsmp, cnid);
+       if (cp) {
+               if (cp->c_attr.ca_recflags & kHFSHasChildLinkMask) {
+                       retval = 0;
+               } else {
+                       cp->c_attr.ca_recflags |= kHFSHasChildLinkMask;
+                       retval = 1;
+               }
+       }
+       hfs_chash_unlock(hfsmp);
+
+       return retval;
+}