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 997d247ae1acc47a727293729d958b3393dc1ef7..b162a53b2cd502f53e3f615ba168a3988eef6793 100644 (file)
--- a/bsd/hfs/hfs_chash.c
+++ b/bsd/hfs/hfs_chash.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2008 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2002-2012 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
@@ -108,11 +108,7 @@ static void hfs_chash_lock_spin(struct hfsmount *hfsmp)
        lck_mtx_lock_spin(&hfsmp->hfs_chash_mutex);
 }
 
-#ifdef i386
-static void hfs_chash_lock_convert (struct hfsmount *hfsmp)
-#else
 static void hfs_chash_lock_convert (__unused struct hfsmount *hfsmp)
-#endif
 {
        lck_mtx_convert_spin(&hfsmp->hfs_chash_mutex);
 }
@@ -188,7 +184,7 @@ loop:
                         */
                        return (NULL);
                }
-               if (!skiplock && hfs_lock(cp, HFS_EXCLUSIVE_LOCK) != 0) {
+               if (!skiplock && hfs_lock(cp, HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                        vnode_put(vp);
                        return (NULL);
                }
@@ -202,12 +198,12 @@ loop:
                 */
                if (!allow_deleted) {
                        if (cp->c_flag & (C_NOEXISTS | C_DELETED)) {
-                               if (!skiplock)
-                                               hfs_unlock(cp);
+                               if (!skiplock) {
+                                       hfs_unlock(cp);
+                               }
                                vnode_put(vp);
-       
                                return (NULL);
-                       }
+                       }                       
                }
                return (vp);
        }
@@ -226,7 +222,7 @@ exit:
  * 
  */
 int
-hfs_chash_snoop(struct hfsmount *hfsmp, ino_t inum, int (*callout)(const struct cat_desc *,
+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;
@@ -242,7 +238,27 @@ hfs_chash_snoop(struct hfsmount *hfsmp, ino_t inum, int (*callout)(const struct
        for (cp = CNODEHASH(hfsmp, inum)->lh_first; cp; cp = cp->c_hash.le_next) {
                if (cp->c_fileid != inum)
                        continue;
-              /* Skip cnodes that have been removed from the catalog */
+       
+               /*
+                * 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;
                }
@@ -322,17 +338,17 @@ loop_with_lock:
                                goto loop;
                }
                if (ncp) {
-                       /*
+                       /*
                         * someone else won the race to create
                         * this cnode and add it to the hash
                         * just dump our allocation
                         */
-                   FREE_ZONE(ncp, sizeof(struct cnode), M_HFSNODE);
+                       FREE_ZONE(ncp, sizeof(struct cnode), M_HFSNODE);
                        ncp = NULL;
                }
 
                if (!skiplock) {
-                       hfs_lock(cp, HFS_FORCE_LOCK);
+                       hfs_lock(cp, HFS_EXCLUSIVE_LOCK, HFS_LOCK_ALLOW_NOEXISTS);
                }
 
                /*
@@ -356,9 +372,8 @@ loop_with_lock:
                                vnode_put(vp);
                        } else {
                                hfs_chash_lock_spin(hfsmp);
-                       CLR(cp->c_hflag, H_ATTACH);
+                               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);
@@ -383,7 +398,8 @@ loop_with_lock:
 
        if (ncp == NULL) {
                hfs_chash_unlock(hfsmp);
-           MALLOC_ZONE(ncp, struct cnode *, sizeof(struct cnode), M_HFSNODE, M_WAITOK);
+
+               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
@@ -403,7 +419,7 @@ loop_with_lock:
 
        lck_rw_init(&ncp->c_rwlock, hfs_rwlock_group, hfs_lock_attr);
        if (!skiplock)
-               (void) hfs_lock(ncp, HFS_EXCLUSIVE_LOCK);
+               (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);