Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1764 insertions, 0 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
new file mode 100644
index 000000000000..496a4e08369c
--- /dev/null
+++ b/fs/dcache.c
@@ -0,0 +1,1764 @@
+/*
+ * fs/dcache.c
+ *
+ * Complete reimplementation
+ * (C) 1997 Thomas Schoebel-Theuer,
+ * with heavy changes by Linus Torvalds
+ */
+
+/*
+ * Notes on the allocation strategy:
+ *
+ * The dcache is a master of the icache - whenever a dcache entry
+ * exists, the inode will always exist. "iput()" is done either when
+ * the dcache entry is deleted or garbage collected.
+ */
+
+#include <linux/config.h>
+#include <linux/syscalls.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/smp_lock.h>
+#include <linux/hash.h>
+#include <linux/cache.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/file.h>
+#include <asm/uaccess.h>
+#include <linux/security.h>
+#include <linux/seqlock.h>
+#include <linux/swap.h>
+#include <linux/bootmem.h>
+
+/* #define DCACHE_DEBUG 1 */
+
+int sysctl_vfs_cache_pressure = 100;
+EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
+
+ __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
+seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
+
+EXPORT_SYMBOL(dcache_lock);
+
+static kmem_cache_t *dentry_cache; 
+
+#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
+
+/*
+ * This is the single most critical data structure when it comes
+ * to the dcache: the hashtable for lookups. Somebody should try
+ * to make this good - I've just made it work.
+ *
+ * This hash-function tries to avoid losing too many bits of hash
+ * information, yet avoid using a prime hash-size or similar.
+ */
+#define D_HASHBITS     d_hash_shift
+#define D_HASHMASK     d_hash_mask
+
+static unsigned int d_hash_mask;
+static unsigned int d_hash_shift;
+static struct hlist_head *dentry_hashtable;
+static LIST_HEAD(dentry_unused);
+
+/* Statistics gathering. */
+struct dentry_stat_t dentry_stat = {
+        .age_limit = 45,
+};
+
+static void d_callback(struct rcu_head *head)
+{
+        struct dentry * dentry = container_of(head, struct dentry, d_rcu);
+
+        if (dname_external(dentry))
+                kfree(dentry->d_name.name);
+        kmem_cache_free(dentry_cache, dentry); 
+}
+
+/*
+ * no dcache_lock, please.  The caller must decrement dentry_stat.nr_dentry
+ * inside dcache_lock.
+ */
+static void d_free(struct dentry *dentry)
+{
+        if (dentry->d_op && dentry->d_op->d_release)
+                dentry->d_op->d_release(dentry);
+        call_rcu(&dentry->d_rcu, d_callback);
+}
+
+/*
+ * Release the dentry's inode, using the filesystem
+ * d_iput() operation if defined.
+ * Called with dcache_lock and per dentry lock held, drops both.
+ */
+static inline void dentry_iput(struct dentry * dentry)
+{
+        struct inode *inode = dentry->d_inode;
+        if (inode) {
+                dentry->d_inode = NULL;
+                list_del_init(&dentry->d_alias);
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&dcache_lock);
+                if (dentry->d_op && dentry->d_op->d_iput)
+                        dentry->d_op->d_iput(dentry, inode);
+                else
+                        iput(inode);
+        } else {
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&dcache_lock);
+        }
+}
+
+/* 
+ * This is dput
+ *
+ * This is complicated by the fact that we do not want to put
+ * dentries that are no longer on any hash chain on the unused
+ * list: we'd much rather just get rid of them immediately.
+ *
+ * However, that implies that we have to traverse the dentry
+ * tree upwards to the parents which might _also_ now be
+ * scheduled for deletion (it may have been only waiting for
+ * its last child to go away).
+ *
+ * This tail recursion is done by hand as we don't want to depend
+ * on the compiler to always get this right (gcc generally doesn't).
+ * Real recursion would eat up our stack space.
+ */
+
+/*
+ * dput - release a dentry
+ * @dentry: dentry to release 
+ *
+ * Release a dentry. This will drop the usage count and if appropriate
+ * call the dentry unlink method as well as removing it from the queues and
+ * releasing its resources. If the parent dentries were scheduled for release
+ * they too may now get deleted.
+ *
+ * no dcache lock, please.
+ */
+
+void dput(struct dentry *dentry)
+{
+        if (!dentry)
+                return;
+
+repeat:
+        if (atomic_read(&dentry->d_count) == 1)
+                might_sleep();
+        if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
+                return;
+
+        spin_lock(&dentry->d_lock);
+        if (atomic_read(&dentry->d_count)) {
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&dcache_lock);
+                return;
+        }
+
+        /*
+         * AV: ->d_delete() is _NOT_ allowed to block now.
+         */
+        if (dentry->d_op && dentry->d_op->d_delete) {
+                if (dentry->d_op->d_delete(dentry))
+                        goto unhash_it;
+        }
+        /* Unreachable? Get rid of it */
+        if (d_unhashed(dentry))
+                goto kill_it;
+        if (list_empty(&dentry->d_lru)) {
+                dentry->d_flags |= DCACHE_REFERENCED;
+                list_add(&dentry->d_lru, &dentry_unused);
+                dentry_stat.nr_unused++;
+        }
+        spin_unlock(&dentry->d_lock);
+        spin_unlock(&dcache_lock);
+        return;
+
+unhash_it:
+        __d_drop(dentry);
+
+kill_it: {
+                struct dentry *parent;
+
+                /* If dentry was on d_lru list
+                 * delete it from there
+                 */
+                if (!list_empty(&dentry->d_lru)) {
+                        list_del(&dentry->d_lru);
+                        dentry_stat.nr_unused--;
+                }
+                list_del(&dentry->d_child);
+                dentry_stat.nr_dentry--;        /* For d_free, below */
+                /*drops the locks, at that point nobody can reach this dentry */
+                dentry_iput(dentry);
+                parent = dentry->d_parent;
+                d_free(dentry);
+                if (dentry == parent)
+                        return;
+                dentry = parent;
+                goto repeat;
+        }
+}
+
+/**
+ * d_invalidate - invalidate a dentry
+ * @dentry: dentry to invalidate
+ *
+ * Try to invalidate the dentry if it turns out to be
+ * possible. If there are other dentries that can be
+ * reached through this one we can't delete it and we
+ * return -EBUSY. On success we return 0.
+ *
+ * no dcache lock.
+ */
+ 
+int d_invalidate(struct dentry * dentry)
+{
+        /*
+         * If it's already been dropped, return OK.
+         */
+        spin_lock(&dcache_lock);
+        if (d_unhashed(dentry)) {
+                spin_unlock(&dcache_lock);
+                return 0;
+        }
+        /*
+         * Check whether to do a partial shrink_dcache
+         * to get rid of unused child entries.
+         */
+        if (!list_empty(&dentry->d_subdirs)) {
+                spin_unlock(&dcache_lock);
+                shrink_dcache_parent(dentry);
+                spin_lock(&dcache_lock);
+        }
+
+        /*
+         * Somebody else still using it?
+         *
+         * If it's a directory, we can't drop it
+         * for fear of somebody re-populating it
+         * with children (even though dropping it
+         * would make it unreachable from the root,
+         * we might still populate it if it was a
+         * working directory or similar).
+         */
+        spin_lock(&dentry->d_lock);
+        if (atomic_read(&dentry->d_count) > 1) {
+                if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
+                        spin_unlock(&dentry->d_lock);
+                        spin_unlock(&dcache_lock);
+                        return -EBUSY;
+                }
+        }
+
+        __d_drop(dentry);
+        spin_unlock(&dentry->d_lock);
+        spin_unlock(&dcache_lock);
+        return 0;
+}
+
+/* This should be called _only_ with dcache_lock held */
+
+static inline struct dentry * __dget_locked(struct dentry *dentry)
+{
+        atomic_inc(&dentry->d_count);
+        if (!list_empty(&dentry->d_lru)) {
+                dentry_stat.nr_unused--;
+                list_del_init(&dentry->d_lru);
+        }
+        return dentry;
+}
+
+struct dentry * dget_locked(struct dentry *dentry)
+{
+        return __dget_locked(dentry);
+}
+
+/**
+ * d_find_alias - grab a hashed alias of inode
+ * @inode: inode in question
+ * @want_discon:  flag, used by d_splice_alias, to request
+ *          that only a DISCONNECTED alias be returned.
+ *
+ * If inode has a hashed alias, or is a directory and has any alias,
+ * acquire the reference to alias and return it. Otherwise return NULL.
+ * Notice that if inode is a directory there can be only one alias and
+ * it can be unhashed only if it has no children, or if it is the root
+ * of a filesystem.
+ *
+ * If the inode has a DCACHE_DISCONNECTED alias, then prefer
+ * any other hashed alias over that one unless @want_discon is set,
+ * in which case only return a DCACHE_DISCONNECTED alias.
+ */
+
+static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
+{
+        struct list_head *head, *next, *tmp;
+        struct dentry *alias, *discon_alias=NULL;
+
+        head = &inode->i_dentry;
+        next = inode->i_dentry.next;
+        while (next != head) {
+                tmp = next;
+                next = tmp->next;
+                prefetch(next);
+                alias = list_entry(tmp, struct dentry, d_alias);
+                if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
+                        if (alias->d_flags & DCACHE_DISCONNECTED)
+                                discon_alias = alias;
+                        else if (!want_discon) {
+                                __dget_locked(alias);
+                                return alias;
+                        }
+                }
+        }
+        if (discon_alias)
+                __dget_locked(discon_alias);
+        return discon_alias;
+}
+
+struct dentry * d_find_alias(struct inode *inode)
+{
+        struct dentry *de;
+        spin_lock(&dcache_lock);
+        de = __d_find_alias(inode, 0);
+        spin_unlock(&dcache_lock);
+        return de;
+}
+
+/*
+ *      Try to kill dentries associated with this inode.
+ * WARNING: you must own a reference to inode.
+ */
+void d_prune_aliases(struct inode *inode)
+{
+        struct list_head *tmp, *head = &inode->i_dentry;
+restart:
+        spin_lock(&dcache_lock);
+        tmp = head;
+        while ((tmp = tmp->next) != head) {
+                struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
+                spin_lock(&dentry->d_lock);
+                if (!atomic_read(&dentry->d_count)) {
+                        __dget_locked(dentry);
+                        __d_drop(dentry);
+                        spin_unlock(&dentry->d_lock);
+                        spin_unlock(&dcache_lock);
+                        dput(dentry);
+                        goto restart;
+                }
+                spin_unlock(&dentry->d_lock);
+        }
+        spin_unlock(&dcache_lock);
+}
+
+/*
+ * Throw away a dentry - free the inode, dput the parent.
+ * This requires that the LRU list has already been
+ * removed.
+ * Called with dcache_lock, drops it and then regains.
+ */
+static inline void prune_one_dentry(struct dentry * dentry)
+{
+        struct dentry * parent;
+
+        __d_drop(dentry);
+        list_del(&dentry->d_child);
+        dentry_stat.nr_dentry--;        /* For d_free, below */
+        dentry_iput(dentry);
+        parent = dentry->d_parent;
+        d_free(dentry);
+        if (parent != dentry)
+                dput(parent);
+        spin_lock(&dcache_lock);
+}
+
+/**
+ * prune_dcache - shrink the dcache
+ * @count: number of entries to try and free
+ *
+ * Shrink the dcache. This is done when we need
+ * more memory, or simply when we need to unmount
+ * something (at which point we need to unuse
+ * all dentries).
+ *
+ * This function may fail to free any resources if
+ * all the dentries are in use.
+ */
+ 
+static void prune_dcache(int count)
+{
+        spin_lock(&dcache_lock);
+        for (; count ; count--) {
+                struct dentry *dentry;
+                struct list_head *tmp;
+
+                cond_resched_lock(&dcache_lock);
+
+                tmp = dentry_unused.prev;
+                if (tmp == &dentry_unused)
+                        break;
+                list_del_init(tmp);
+                prefetch(dentry_unused.prev);
+                dentry_stat.nr_unused--;
+                dentry = list_entry(tmp, struct dentry, d_lru);
+
+                spin_lock(&dentry->d_lock);
+                /*
+                 * We found an inuse dentry which was not removed from
+                 * dentry_unused because of laziness during lookup.  Do not free
+                 * it - just keep it off the dentry_unused list.
+                 */
+                if (atomic_read(&dentry->d_count)) {
+                        spin_unlock(&dentry->d_lock);
+                        continue;
+                }
+                /* If the dentry was recently referenced, don't free it. */
+                if (dentry->d_flags & DCACHE_REFERENCED) {
+                        dentry->d_flags &= ~DCACHE_REFERENCED;
+                        list_add(&dentry->d_lru, &dentry_unused);
+                        dentry_stat.nr_unused++;
+                        spin_unlock(&dentry->d_lock);
+                        continue;
+                }
+                prune_one_dentry(dentry);
+        }
+        spin_unlock(&dcache_lock);
+}
+
+/*
+ * Shrink the dcache for the specified super block.
+ * This allows us to unmount a device without disturbing
+ * the dcache for the other devices.
+ *
+ * This implementation makes just two traversals of the
+ * unused list.  On the first pass we move the selected
+ * dentries to the most recent end, and on the second
+ * pass we free them.  The second pass must restart after
+ * each dput(), but since the target dentries are all at
+ * the end, it's really just a single traversal.
+ */
+
+/**
+ * shrink_dcache_sb - shrink dcache for a superblock
+ * @sb: superblock
+ *
+ * Shrink the dcache for the specified super block. This
+ * is used to free the dcache before unmounting a file
+ * system
+ */
+
+void shrink_dcache_sb(struct super_block * sb)
+{
+        struct list_head *tmp, *next;
+        struct dentry *dentry;
+
+        /*
+         * Pass one ... move the dentries for the specified
+         * superblock to the most recent end of the unused list.
+         */
+        spin_lock(&dcache_lock);
+        next = dentry_unused.next;
+        while (next != &dentry_unused) {
+                tmp = next;
+                next = tmp->next;
+                dentry = list_entry(tmp, struct dentry, d_lru);
+                if (dentry->d_sb != sb)
+                        continue;
+                list_del(tmp);
+                list_add(tmp, &dentry_unused);
+        }
+
+        /*
+         * Pass two ... free the dentries for this superblock.
+         */
+repeat:
+        next = dentry_unused.next;
+        while (next != &dentry_unused) {
+                tmp = next;
+                next = tmp->next;
+                dentry = list_entry(tmp, struct dentry, d_lru);
+                if (dentry->d_sb != sb)
+                        continue;
+                dentry_stat.nr_unused--;
+                list_del_init(tmp);
+                spin_lock(&dentry->d_lock);
+                if (atomic_read(&dentry->d_count)) {
+                        spin_unlock(&dentry->d_lock);
+                        continue;
+                }
+                prune_one_dentry(dentry);
+                goto repeat;
+        }
+        spin_unlock(&dcache_lock);
+}
+
+/*
+ * Search for at least 1 mount point in the dentry's subdirs.
+ * We descend to the next level whenever the d_subdirs
+ * list is non-empty and continue searching.
+ */
+ 
+/**
+ * have_submounts - check for mounts over a dentry
+ * @parent: dentry to check.
+ *
+ * Return true if the parent or its subdirectories contain
+ * a mount point
+ */
+ 
+int have_submounts(struct dentry *parent)
+{
+        struct dentry *this_parent = parent;
+        struct list_head *next;
+
+        spin_lock(&dcache_lock);
+        if (d_mountpoint(parent))
+                goto positive;
+repeat:
+        next = this_parent->d_subdirs.next;
+resume:
+        while (next != &this_parent->d_subdirs) {
+                struct list_head *tmp = next;
+                struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+                next = tmp->next;
+                /* Have we found a mount point ? */
+                if (d_mountpoint(dentry))
+                        goto positive;
+                if (!list_empty(&dentry->d_subdirs)) {
+                        this_parent = dentry;
+                        goto repeat;
+                }
+        }
+        /*
+         * All done at this level ... ascend and resume the search.
+         */
+        if (this_parent != parent) {
+                next = this_parent->d_child.next; 
+                this_parent = this_parent->d_parent;
+                goto resume;
+        }
+        spin_unlock(&dcache_lock);
+        return 0; /* No mount points found in tree */
+positive:
+        spin_unlock(&dcache_lock);
+        return 1;
+}
+
+/*
+ * Search the dentry child list for the specified parent,
+ * and move any unused dentries to the end of the unused
+ * list for prune_dcache(). We descend to the next level
+ * whenever the d_subdirs list is non-empty and continue
+ * searching.
+ *
+ * It returns zero iff there are no unused children,
+ * otherwise  it returns the number of children moved to
+ * the end of the unused list. This may not be the total
+ * number of unused children, because select_parent can
+ * drop the lock and return early due to latency
+ * constraints.
+ */
+static int select_parent(struct dentry * parent)
+{
+        struct dentry *this_parent = parent;
+        struct list_head *next;
+        int found = 0;
+
+        spin_lock(&dcache_lock);
+repeat:
+        next = this_parent->d_subdirs.next;
+resume:
+        while (next != &this_parent->d_subdirs) {
+                struct list_head *tmp = next;
+                struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+                next = tmp->next;
+
+                if (!list_empty(&dentry->d_lru)) {
+                        dentry_stat.nr_unused--;
+                        list_del_init(&dentry->d_lru);
+                }
+                /* 
+                 * move only zero ref count dentries to the end 
+                 * of the unused list for prune_dcache
+                 */
+                if (!atomic_read(&dentry->d_count)) {
+                        list_add(&dentry->d_lru, dentry_unused.prev);
+                        dentry_stat.nr_unused++;
+                        found++;
+                }
+
+                /*
+                 * We can return to the caller if we have found some (this
+                 * ensures forward progress). We'll be coming back to find
+                 * the rest.
+                 */
+                if (found && need_resched())
+                        goto out;
+
+                /*
+                 * Descend a level if the d_subdirs list is non-empty.
+                 */
+                if (!list_empty(&dentry->d_subdirs)) {
+                        this_parent = dentry;
+#ifdef DCACHE_DEBUG
+printk(KERN_DEBUG "select_parent: descending to %s/%s, found=%d\n",
+dentry->d_parent->d_name.name, dentry->d_name.name, found);
+#endif
+                        goto repeat;
+                }
+        }
+        /*
+         * All done at this level ... ascend and resume the search.
+         */
+        if (this_parent != parent) {
+                next = this_parent->d_child.next; 
+                this_parent = this_parent->d_parent;
+#ifdef DCACHE_DEBUG
+printk(KERN_DEBUG "select_parent: ascending to %s/%s, found=%d\n",
+this_parent->d_parent->d_name.name, this_parent->d_name.name, found);
+#endif
+                goto resume;
+        }
+out:
+        spin_unlock(&dcache_lock);
+        return found;
+}
+
+/**
+ * shrink_dcache_parent - prune dcache
+ * @parent: parent of entries to prune
+ *
+ * Prune the dcache to remove unused children of the parent dentry.
+ */
+ 
+void shrink_dcache_parent(struct dentry * parent)
+{
+        int found;
+
+        while ((found = select_parent(parent)) != 0)
+                prune_dcache(found);
+}
+
+/**
+ * shrink_dcache_anon - further prune the cache
+ * @head: head of d_hash list of dentries to prune
+ *
+ * Prune the dentries that are anonymous
+ *
+ * parsing d_hash list does not hlist_for_each_rcu() as it
+ * done under dcache_lock.
+ *
+ */
+void shrink_dcache_anon(struct hlist_head *head)
+{
+        struct hlist_node *lp;
+        int found;
+        do {
+                found = 0;
+                spin_lock(&dcache_lock);
+                hlist_for_each(lp, head) {
+                        struct dentry *this = hlist_entry(lp, struct dentry, d_hash);
+                        if (!list_empty(&this->d_lru)) {
+                                dentry_stat.nr_unused--;
+                                list_del_init(&this->d_lru);
+                        }
+
+                        /* 
+                         * move only zero ref count dentries to the end 
+                         * of the unused list for prune_dcache
+                         */
+                        if (!atomic_read(&this->d_count)) {
+                                list_add_tail(&this->d_lru, &dentry_unused);
+                                dentry_stat.nr_unused++;
+                                found++;
+                        }
+                }
+                spin_unlock(&dcache_lock);
+                prune_dcache(found);
+        } while(found);
+}
+
+/*
+ * Scan `nr' dentries and return the number which remain.
+ *
+ * We need to avoid reentering the filesystem if the caller is performing a
+ * GFP_NOFS allocation attempt.  One example deadlock is:
+ *
+ * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
+ * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
+ * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
+ *
+ * In this case we return -1 to tell the caller that we baled.
+ */
+static int shrink_dcache_memory(int nr, unsigned int gfp_mask)
+{
+        if (nr) {
+                if (!(gfp_mask & __GFP_FS))
+                        return -1;
+                prune_dcache(nr);
+        }
+        return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
+}
+
+/**
+ * d_alloc      -       allocate a dcache entry
+ * @parent: parent of entry to allocate
+ * @name: qstr of the name
+ *
+ * Allocates a dentry. It returns %NULL if there is insufficient memory
+ * available. On a success the dentry is returned. The name passed in is
+ * copied and the copy passed in may be reused after this call.
+ */
+ 
+struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
+{
+        struct dentry *dentry;
+        char *dname;
+
+        dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); 
+        if (!dentry)
+                return NULL;
+
+        if (name->len > DNAME_INLINE_LEN-1) {
+                dname = kmalloc(name->len + 1, GFP_KERNEL);
+                if (!dname) {
+                        kmem_cache_free(dentry_cache, dentry); 
+                        return NULL;
+                }
+        } else  {
+                dname = dentry->d_iname;
+        }       
+        dentry->d_name.name = dname;
+
+        dentry->d_name.len = name->len;
+        dentry->d_name.hash = name->hash;
+        memcpy(dname, name->name, name->len);
+        dname[name->len] = 0;
+
+        atomic_set(&dentry->d_count, 1);
+        dentry->d_flags = DCACHE_UNHASHED;
+        spin_lock_init(&dentry->d_lock);
+        dentry->d_inode = NULL;
+        dentry->d_parent = NULL;
+        dentry->d_sb = NULL;
+        dentry->d_op = NULL;
+        dentry->d_fsdata = NULL;
+        dentry->d_mounted = 0;
+        dentry->d_cookie = NULL;
+        INIT_HLIST_NODE(&dentry->d_hash);
+        INIT_LIST_HEAD(&dentry->d_lru);
+        INIT_LIST_HEAD(&dentry->d_subdirs);
+        INIT_LIST_HEAD(&dentry->d_alias);
+
+        if (parent) {
+                dentry->d_parent = dget(parent);
+                dentry->d_sb = parent->d_sb;
+        } else {
+                INIT_LIST_HEAD(&dentry->d_child);
+        }
+
+        spin_lock(&dcache_lock);
+        if (parent)
+                list_add(&dentry->d_child, &parent->d_subdirs);
+        dentry_stat.nr_dentry++;
+        spin_unlock(&dcache_lock);
+
+        return dentry;
+}
+
+struct dentry *d_alloc_name(struct dentry *parent, const char *name)
+{
+        struct qstr q;
+
+        q.name = name;
+        q.len = strlen(name);
+        q.hash = full_name_hash(q.name, q.len);
+        return d_alloc(parent, &q);
+}
+
+/**
+ * d_instantiate - fill in inode information for a dentry
+ * @entry: dentry to complete
+ * @inode: inode to attach to this dentry
+ *
+ * Fill in inode information in the entry.
+ *
+ * This turns negative dentries into productive full members
+ * of society.
+ *
+ * NOTE! This assumes that the inode count has been incremented
+ * (or otherwise set) by the caller to indicate that it is now
+ * in use by the dcache.
+ */
+ 
+void d_instantiate(struct dentry *entry, struct inode * inode)
+{
+        if (!list_empty(&entry->d_alias)) BUG();
+        spin_lock(&dcache_lock);
+        if (inode)
+                list_add(&entry->d_alias, &inode->i_dentry);
+        entry->d_inode = inode;
+        spin_unlock(&dcache_lock);
+        security_d_instantiate(entry, inode);
+}
+
+/**
+ * d_instantiate_unique - instantiate a non-aliased dentry
+ * @entry: dentry to instantiate
+ * @inode: inode to attach to this dentry
+ *
+ * Fill in inode information in the entry. On success, it returns NULL.
+ * If an unhashed alias of "entry" already exists, then we return the
+ * aliased dentry instead.
+ *
+ * Note that in order to avoid conflicts with rename() etc, the caller
+ * had better be holding the parent directory semaphore.
+ */
+struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
+{
+        struct dentry *alias;
+        int len = entry->d_name.len;
+        const char *name = entry->d_name.name;
+        unsigned int hash = entry->d_name.hash;
+
+        BUG_ON(!list_empty(&entry->d_alias));
+        spin_lock(&dcache_lock);
+        if (!inode)
+                goto do_negative;
+        list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+                struct qstr *qstr = &alias->d_name;
+
+                if (qstr->hash != hash)
+                        continue;
+                if (alias->d_parent != entry->d_parent)
+                        continue;
+                if (qstr->len != len)
+                        continue;
+                if (memcmp(qstr->name, name, len))
+                        continue;
+                dget_locked(alias);
+                spin_unlock(&dcache_lock);
+                BUG_ON(!d_unhashed(alias));
+                return alias;
+        }
+        list_add(&entry->d_alias, &inode->i_dentry);
+do_negative:
+        entry->d_inode = inode;
+        spin_unlock(&dcache_lock);
+        security_d_instantiate(entry, inode);
+        return NULL;
+}
+EXPORT_SYMBOL(d_instantiate_unique);
+
+/**
+ * d_alloc_root - allocate root dentry
+ * @root_inode: inode to allocate the root for
+ *
+ * Allocate a root ("/") dentry for the inode given. The inode is
+ * instantiated and returned. %NULL is returned if there is insufficient
+ * memory or the inode passed is %NULL.
+ */
+ 
+struct dentry * d_alloc_root(struct inode * root_inode)
+{
+        struct dentry *res = NULL;
+
+        if (root_inode) {
+                static const struct qstr name = { .name = "/", .len = 1 };
+
+                res = d_alloc(NULL, &name);
+                if (res) {
+                        res->d_sb = root_inode->i_sb;
+                        res->d_parent = res;
+                        d_instantiate(res, root_inode);
+                }
+        }
+        return res;
+}
+
+static inline struct hlist_head *d_hash(struct dentry *parent,
+                                        unsigned long hash)
+{
+        hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
+        hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
+        return dentry_hashtable + (hash & D_HASHMASK);
+}
+
+/**
+ * d_alloc_anon - allocate an anonymous dentry
+ * @inode: inode to allocate the dentry for
+ *
+ * This is similar to d_alloc_root.  It is used by filesystems when
+ * creating a dentry for a given inode, often in the process of 
+ * mapping a filehandle to a dentry.  The returned dentry may be
+ * anonymous, or may have a full name (if the inode was already
+ * in the cache).  The file system may need to make further
+ * efforts to connect this dentry into the dcache properly.
+ *
+ * When called on a directory inode, we must ensure that
+ * the inode only ever has one dentry.  If a dentry is
+ * found, that is returned instead of allocating a new one.
+ *
+ * On successful return, the reference to the inode has been transferred
+ * to the dentry.  If %NULL is returned (indicating kmalloc failure),
+ * the reference on the inode has not been released.
+ */
+
+struct dentry * d_alloc_anon(struct inode *inode)
+{
+        static const struct qstr anonstring = { .name = "" };
+        struct dentry *tmp;
+        struct dentry *res;
+
+        if ((res = d_find_alias(inode))) {
+                iput(inode);
+                return res;
+        }
+
+        tmp = d_alloc(NULL, &anonstring);
+        if (!tmp)
+                return NULL;
+
+        tmp->d_parent = tmp; /* make sure dput doesn't croak */
+        
+        spin_lock(&dcache_lock);
+        res = __d_find_alias(inode, 0);
+        if (!res) {
+                /* attach a disconnected dentry */
+                res = tmp;
+                tmp = NULL;
+                spin_lock(&res->d_lock);
+                res->d_sb = inode->i_sb;
+                res->d_parent = res;
+                res->d_inode = inode;
+                res->d_flags |= DCACHE_DISCONNECTED;
+                res->d_flags &= ~DCACHE_UNHASHED;
+                list_add(&res->d_alias, &inode->i_dentry);
+                hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
+                spin_unlock(&res->d_lock);
+
+                inode = NULL; /* don't drop reference */
+        }
+        spin_unlock(&dcache_lock);
+
+        if (inode)
+                iput(inode);
+        if (tmp)
+                dput(tmp);
+        return res;
+}
+
+
+/**
+ * d_splice_alias - splice a disconnected dentry into the tree if one exists
+ * @inode:  the inode which may have a disconnected dentry
+ * @dentry: a negative dentry which we want to point to the inode.
+ *
+ * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
+ * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
+ * and return it, else simply d_add the inode to the dentry and return NULL.
+ *
+ * This is needed in the lookup routine of any filesystem that is exportable
+ * (via knfsd) so that we can build dcache paths to directories effectively.
+ *
+ * If a dentry was found and moved, then it is returned.  Otherwise NULL
+ * is returned.  This matches the expected return value of ->lookup.
+ *
+ */
+struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
+{
+        struct dentry *new = NULL;
+
+        if (inode) {
+                spin_lock(&dcache_lock);
+                new = __d_find_alias(inode, 1);
+                if (new) {
+                        BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
+                        spin_unlock(&dcache_lock);
+                        security_d_instantiate(new, inode);
+                        d_rehash(dentry);
+                        d_move(new, dentry);
+                        iput(inode);
+                } else {
+                        /* d_instantiate takes dcache_lock, so we do it by hand */
+                        list_add(&dentry->d_alias, &inode->i_dentry);
+                        dentry->d_inode = inode;
+                        spin_unlock(&dcache_lock);
+                        security_d_instantiate(dentry, inode);
+                        d_rehash(dentry);
+                }
+        } else
+                d_add(dentry, inode);
+        return new;
+}
+
+
+/**
+ * d_lookup - search for a dentry
+ * @parent: parent dentry
+ * @name: qstr of name we wish to find
+ *
+ * Searches the children of the parent dentry for the name in question. If
+ * the dentry is found its reference count is incremented and the dentry
+ * is returned. The caller must use d_put to free the entry when it has
+ * finished using it. %NULL is returned on failure.
+ *
+ * __d_lookup is dcache_lock free. The hash list is protected using RCU.
+ * Memory barriers are used while updating and doing lockless traversal. 
+ * To avoid races with d_move while rename is happening, d_lock is used.
+ *
+ * Overflows in memcmp(), while d_move, are avoided by keeping the length
+ * and name pointer in one structure pointed by d_qstr.
+ *
+ * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
+ * lookup is going on.
+ *
+ * dentry_unused list is not updated even if lookup finds the required dentry
+ * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
+ * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
+ * acquisition.
+ *
+ * d_lookup() is protected against the concurrent renames in some unrelated
+ * directory using the seqlockt_t rename_lock.
+ */
+
+struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
+{
+        struct dentry * dentry = NULL;
+        unsigned long seq;
+
+        do {
+                seq = read_seqbegin(&rename_lock);
+                dentry = __d_lookup(parent, name);
+                if (dentry)
+                        break;
+        } while (read_seqretry(&rename_lock, seq));
+        return dentry;
+}
+
+struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
+{
+        unsigned int len = name->len;
+        unsigned int hash = name->hash;
+        const unsigned char *str = name->name;
+        struct hlist_head *head = d_hash(parent,hash);
+        struct dentry *found = NULL;
+        struct hlist_node *node;
+
+        rcu_read_lock();
+        
+        hlist_for_each_rcu(node, head) {
+                struct dentry *dentry; 
+                struct qstr *qstr;
+
+                dentry = hlist_entry(node, struct dentry, d_hash);
+
+                if (dentry->d_name.hash != hash)
+                        continue;
+                if (dentry->d_parent != parent)
+                        continue;
+
+                spin_lock(&dentry->d_lock);
+
+                /*
+                 * Recheck the dentry after taking the lock - d_move may have
+                 * changed things.  Don't bother checking the hash because we're
+                 * about to compare the whole name anyway.
+                 */
+                if (dentry->d_parent != parent)
+                        goto next;
+
+                /*
+                 * It is safe to compare names since d_move() cannot
+                 * change the qstr (protected by d_lock).
+                 */
+                qstr = &dentry->d_name;
+                if (parent->d_op && parent->d_op->d_compare) {
+                        if (parent->d_op->d_compare(parent, qstr, name))
+                                goto next;
+                } else {
+                        if (qstr->len != len)
+                                goto next;
+                        if (memcmp(qstr->name, str, len))
+                                goto next;
+                }
+
+                if (!d_unhashed(dentry)) {
+                        atomic_inc(&dentry->d_count);
+                        found = dentry;
+                }
+                spin_unlock(&dentry->d_lock);
+                break;
+next:
+                spin_unlock(&dentry->d_lock);
+        }
+        rcu_read_unlock();
+
+        return found;
+}
+
+/**
+ * d_validate - verify dentry provided from insecure source
+ * @dentry: The dentry alleged to be valid child of @dparent
+ * @dparent: The parent dentry (known to be valid)
+ * @hash: Hash of the dentry
+ * @len: Length of the name
+ *
+ * An insecure source has sent us a dentry, here we verify it and dget() it.
+ * This is used by ncpfs in its readdir implementation.
+ * Zero is returned in the dentry is invalid.
+ */
+ 
+int d_validate(struct dentry *dentry, struct dentry *dparent)
+{
+        struct hlist_head *base;
+        struct hlist_node *lhp;
+
+        /* Check whether the ptr might be valid at all.. */
+        if (!kmem_ptr_validate(dentry_cache, dentry))
+                goto out;
+
+        if (dentry->d_parent != dparent)
+                goto out;
+
+        spin_lock(&dcache_lock);
+        base = d_hash(dparent, dentry->d_name.hash);
+        hlist_for_each(lhp,base) { 
+                /* hlist_for_each_rcu() not required for d_hash list
+                 * as it is parsed under dcache_lock
+                 */
+                if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
+                        __dget_locked(dentry);
+                        spin_unlock(&dcache_lock);
+                        return 1;
+                }
+        }
+        spin_unlock(&dcache_lock);
+out:
+        return 0;
+}
+
+/*
+ * When a file is deleted, we have two options:
+ * - turn this dentry into a negative dentry
+ * - unhash this dentry and free it.
+ *
+ * Usually, we want to just turn this into
+ * a negative dentry, but if anybody else is
+ * currently using the dentry or the inode
+ * we can't do that and we fall back on removing
+ * it from the hash queues and waiting for
+ * it to be deleted later when it has no users
+ */
+ 
+/**
+ * d_delete - delete a dentry
+ * @dentry: The dentry to delete
+ *
+ * Turn the dentry into a negative dentry if possible, otherwise
+ * remove it from the hash queues so it can be deleted later
+ */
+ 
+void d_delete(struct dentry * dentry)
+{
+        /*
+         * Are we the only user?
+         */
+        spin_lock(&dcache_lock);
+        spin_lock(&dentry->d_lock);
+        if (atomic_read(&dentry->d_count) == 1) {
+                dentry_iput(dentry);
+                return;
+        }
+
+        if (!d_unhashed(dentry))
+                __d_drop(dentry);
+
+        spin_unlock(&dentry->d_lock);
+        spin_unlock(&dcache_lock);
+}
+
+static void __d_rehash(struct dentry * entry, struct hlist_head *list)
+{
+
+        entry->d_flags &= ~DCACHE_UNHASHED;
+        hlist_add_head_rcu(&entry->d_hash, list);
+}
+
+/**
+ * d_rehash     - add an entry back to the hash
+ * @entry: dentry to add to the hash
+ *
+ * Adds a dentry to the hash according to its name.
+ */
+ 
+void d_rehash(struct dentry * entry)
+{
+        struct hlist_head *list = d_hash(entry->d_parent, entry->d_name.hash);
+
+        spin_lock(&dcache_lock);
+        spin_lock(&entry->d_lock);
+        __d_rehash(entry, list);
+        spin_unlock(&entry->d_lock);
+        spin_unlock(&dcache_lock);
+}
+
+#define do_switch(x,y) do { \
+        __typeof__ (x) __tmp = x; \
+        x = y; y = __tmp; } while (0)
+
+/*
+ * When switching names, the actual string doesn't strictly have to
+ * be preserved in the target - because we're dropping the target
+ * anyway. As such, we can just do a simple memcpy() to copy over
+ * the new name before we switch.
+ *
+ * Note that we have to be a lot more careful about getting the hash
+ * switched - we have to switch the hash value properly even if it
+ * then no longer matches the actual (corrupted) string of the target.
+ * The hash value has to match the hash queue that the dentry is on..
+ */
+static void switch_names(struct dentry *dentry, struct dentry *target)
+{
+        if (dname_external(target)) {
+                if (dname_external(dentry)) {
+                        /*
+                         * Both external: swap the pointers
+                         */
+                        do_switch(target->d_name.name, dentry->d_name.name);
+                } else {
+                        /*
+                         * dentry:internal, target:external.  Steal target's
+                         * storage and make target internal.
+                         */
+                        dentry->d_name.name = target->d_name.name;
+                        target->d_name.name = target->d_iname;
+                }
+        } else {
+                if (dname_external(dentry)) {
+                        /*
+                         * dentry:external, target:internal.  Give dentry's
+                         * storage to target and make dentry internal
+                         */
+                        memcpy(dentry->d_iname, target->d_name.name,
+                                        target->d_name.len + 1);
+                        target->d_name.name = dentry->d_name.name;
+                        dentry->d_name.name = dentry->d_iname;
+                } else {
+                        /*
+                         * Both are internal.  Just copy target to dentry
+                         */
+                        memcpy(dentry->d_iname, target->d_name.name,
+                                        target->d_name.len + 1);
+                }
+        }
+}
+
+/*
+ * We cannibalize "target" when moving dentry on top of it,
+ * because it's going to be thrown away anyway. We could be more
+ * polite about it, though.
+ *
+ * This forceful removal will result in ugly /proc output if
+ * somebody holds a file open that got deleted due to a rename.
+ * We could be nicer about the deleted file, and let it show
+ * up under the name it got deleted rather than the name that
+ * deleted it.
+ */
+ 
+/**
+ * d_move - move a dentry
+ * @dentry: entry to move
+ * @target: new dentry
+ *
+ * Update the dcache to reflect the move of a file name. Negative
+ * dcache entries should not be moved in this way.
+ */
+
+void d_move(struct dentry * dentry, struct dentry * target)
+{
+        struct hlist_head *list;
+
+        if (!dentry->d_inode)
+                printk(KERN_WARNING "VFS: moving negative dcache entry\n");
+
+        spin_lock(&dcache_lock);
+        write_seqlock(&rename_lock);
+        /*
+         * XXXX: do we really need to take target->d_lock?
+         */
+        if (target < dentry) {
+                spin_lock(&target->d_lock);
+                spin_lock(&dentry->d_lock);
+        } else {
+                spin_lock(&dentry->d_lock);
+                spin_lock(&target->d_lock);
+        }
+
+        /* Move the dentry to the target hash queue, if on different bucket */
+        if (dentry->d_flags & DCACHE_UNHASHED)
+                goto already_unhashed;
+
+        hlist_del_rcu(&dentry->d_hash);
+
+already_unhashed:
+        list = d_hash(target->d_parent, target->d_name.hash);
+        __d_rehash(dentry, list);
+
+        /* Unhash the target: dput() will then get rid of it */
+        __d_drop(target);
+
+        list_del(&dentry->d_child);
+        list_del(&target->d_child);
+
+        /* Switch the names.. */
+        switch_names(dentry, target);
+        do_switch(dentry->d_name.len, target->d_name.len);
+        do_switch(dentry->d_name.hash, target->d_name.hash);
+
+        /* ... and switch the parents */
+        if (IS_ROOT(dentry)) {
+                dentry->d_parent = target->d_parent;
+                target->d_parent = target;
+                INIT_LIST_HEAD(&target->d_child);
+        } else {
+                do_switch(dentry->d_parent, target->d_parent);
+
+                /* And add them back to the (new) parent lists */
+                list_add(&target->d_child, &target->d_parent->d_subdirs);
+        }
+
+        list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
+        spin_unlock(&target->d_lock);
+        spin_unlock(&dentry->d_lock);
+        write_sequnlock(&rename_lock);
+        spin_unlock(&dcache_lock);
+}
+
+/**
+ * d_path - return the path of a dentry
+ * @dentry: dentry to report
+ * @vfsmnt: vfsmnt to which the dentry belongs
+ * @root: root dentry
+ * @rootmnt: vfsmnt to which the root dentry belongs
+ * @buffer: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name. If the entry has been deleted
+ * the string " (deleted)" is appended. Note that this is ambiguous.
+ *
+ * Returns the buffer or an error code if the path was too long.
+ *
+ * "buflen" should be positive. Caller holds the dcache_lock.
+ */
+static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
+                        struct dentry *root, struct vfsmount *rootmnt,
+                        char *buffer, int buflen)
+{
+        char * end = buffer+buflen;
+        char * retval;
+        int namelen;
+
+        *--end = '\0';
+        buflen--;
+        if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
+                buflen -= 10;
+                end -= 10;
+                if (buflen < 0)
+                        goto Elong;
+                memcpy(end, " (deleted)", 10);
+        }
+
+        if (buflen < 1)
+                goto Elong;
+        /* Get '/' right */
+        retval = end-1;
+        *retval = '/';
+
+        for (;;) {
+                struct dentry * parent;
+
+                if (dentry == root && vfsmnt == rootmnt)
+                        break;
+                if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+                        /* Global root? */
+                        spin_lock(&vfsmount_lock);
+                        if (vfsmnt->mnt_parent == vfsmnt) {
+                                spin_unlock(&vfsmount_lock);
+                                goto global_root;
+                        }
+                        dentry = vfsmnt->mnt_mountpoint;
+                        vfsmnt = vfsmnt->mnt_parent;
+                        spin_unlock(&vfsmount_lock);
+                        continue;
+                }
+                parent = dentry->d_parent;
+                prefetch(parent);
+                namelen = dentry->d_name.len;
+                buflen -= namelen + 1;
+                if (buflen < 0)
+                        goto Elong;
+                end -= namelen;
+                memcpy(end, dentry->d_name.name, namelen);
+                *--end = '/';
+                retval = end;
+                dentry = parent;
+        }
+
+        return retval;
+
+global_root:
+        namelen = dentry->d_name.len;
+        buflen -= namelen;
+        if (buflen < 0)
+                goto Elong;
+        retval -= namelen-1;    /* hit the slash */
+        memcpy(retval, dentry->d_name.name, namelen);
+        return retval;
+Elong:
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+/* write full pathname into buffer and return start of pathname */
+char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
+                                char *buf, int buflen)
+{
+        char *res;
+        struct vfsmount *rootmnt;
+        struct dentry *root;
+
+        read_lock(&current->fs->lock);
+        rootmnt = mntget(current->fs->rootmnt);
+        root = dget(current->fs->root);
+        read_unlock(&current->fs->lock);
+        spin_lock(&dcache_lock);
+        res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
+        spin_unlock(&dcache_lock);
+        dput(root);
+        mntput(rootmnt);
+        return res;
+}
+
+/*
+ * NOTE! The user-level library version returns a
+ * character pointer. The kernel system call just
+ * returns the length of the buffer filled (which
+ * includes the ending '\0' character), or a negative
+ * error value. So libc would do something like
+ *
+ *      char *getcwd(char * buf, size_t size)
+ *      {
+ *              int retval;
+ *
+ *              retval = sys_getcwd(buf, size);
+ *              if (retval >= 0)
+ *                      return buf;
+ *              errno = -retval;
+ *              return NULL;
+ *      }
+ */
+asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
+{
+        int error;
+        struct vfsmount *pwdmnt, *rootmnt;
+        struct dentry *pwd, *root;
+        char *page = (char *) __get_free_page(GFP_USER);
+
+        if (!page)
+                return -ENOMEM;
+
+        read_lock(&current->fs->lock);
+        pwdmnt = mntget(current->fs->pwdmnt);
+        pwd = dget(current->fs->pwd);
+        rootmnt = mntget(current->fs->rootmnt);
+        root = dget(current->fs->root);
+        read_unlock(&current->fs->lock);
+
+        error = -ENOENT;
+        /* Has the current directory has been unlinked? */
+        spin_lock(&dcache_lock);
+        if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
+                unsigned long len;
+                char * cwd;
+
+                cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
+                spin_unlock(&dcache_lock);
+
+                error = PTR_ERR(cwd);
+                if (IS_ERR(cwd))
+                        goto out;
+
+                error = -ERANGE;
+                len = PAGE_SIZE + page - cwd;
+                if (len <= size) {
+                        error = len;
+                        if (copy_to_user(buf, cwd, len))
+                                error = -EFAULT;
+                }
+        } else
+                spin_unlock(&dcache_lock);
+
+out:
+        dput(pwd);
+        mntput(pwdmnt);
+        dput(root);
+        mntput(rootmnt);
+        free_page((unsigned long) page);
+        return error;
+}
+
+/*
+ * Test whether new_dentry is a subdirectory of old_dentry.
+ *
+ * Trivially implemented using the dcache structure
+ */
+
+/**
+ * is_subdir - is new dentry a subdirectory of old_dentry
+ * @new_dentry: new dentry
+ * @old_dentry: old dentry
+ *
+ * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
+ * Returns 0 otherwise.
+ * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
+ */
+  
+int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
+{
+        int result;
+        struct dentry * saved = new_dentry;
+        unsigned long seq;
+
+        /* need rcu_readlock to protect against the d_parent trashing due to
+         * d_move
+         */
+        rcu_read_lock();
+        do {
+                /* for restarting inner loop in case of seq retry */
+                new_dentry = saved;
+                result = 0;
+                seq = read_seqbegin(&rename_lock);
+                for (;;) {
+                        if (new_dentry != old_dentry) {
+                                struct dentry * parent = new_dentry->d_parent;
+                                if (parent == new_dentry)
+                                        break;
+                                new_dentry = parent;
+                                continue;
+                        }
+                        result = 1;
+                        break;
+                }
+        } while (read_seqretry(&rename_lock, seq));
+        rcu_read_unlock();
+
+        return result;
+}
+
+void d_genocide(struct dentry *root)
+{
+        struct dentry *this_parent = root;
+        struct list_head *next;
+
+        spin_lock(&dcache_lock);
+repeat:
+        next = this_parent->d_subdirs.next;
+resume:
+        while (next != &this_parent->d_subdirs) {
+                struct list_head *tmp = next;
+                struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+                next = tmp->next;
+                if (d_unhashed(dentry)||!dentry->d_inode)
+                        continue;
+                if (!list_empty(&dentry->d_subdirs)) {
+                        this_parent = dentry;
+                        goto repeat;
+                }
+                atomic_dec(&dentry->d_count);
+        }
+        if (this_parent != root) {
+                next = this_parent->d_child.next; 
+                atomic_dec(&this_parent->d_count);
+                this_parent = this_parent->d_parent;
+                goto resume;
+        }
+        spin_unlock(&dcache_lock);
+}
+
+/**
+ * find_inode_number - check for dentry with name
+ * @dir: directory to check
+ * @name: Name to find.
+ *
+ * Check whether a dentry already exists for the given name,
+ * and return the inode number if it has an inode. Otherwise
+ * 0 is returned.
+ *
+ * This routine is used to post-process directory listings for
+ * filesystems using synthetic inode numbers, and is necessary
+ * to keep getcwd() working.
+ */
+ 
+ino_t find_inode_number(struct dentry *dir, struct qstr *name)
+{
+        struct dentry * dentry;
+        ino_t ino = 0;
+
+        /*
+         * Check for a fs-specific hash function. Note that we must
+         * calculate the standard hash first, as the d_op->d_hash()
+         * routine may choose to leave the hash value unchanged.
+         */
+        name->hash = full_name_hash(name->name, name->len);
+        if (dir->d_op && dir->d_op->d_hash)
+        {
+                if (dir->d_op->d_hash(dir, name) != 0)
+                        goto out;
+        }
+
+        dentry = d_lookup(dir, name);
+        if (dentry)
+        {
+                if (dentry->d_inode)
+                        ino = dentry->d_inode->i_ino;
+                dput(dentry);
+        }
+out:
+        return ino;
+}
+
+static __initdata unsigned long dhash_entries;
+static int __init set_dhash_entries(char *str)
+{
+        if (!str)
+                return 0;
+        dhash_entries = simple_strtoul(str, &str, 0);
+        return 1;
+}
+__setup("dhash_entries=", set_dhash_entries);
+
+static void __init dcache_init_early(void)
+{
+        int loop;
+
+        /* If hashes are distributed across NUMA nodes, defer
+         * hash allocation until vmalloc space is available.
+         */
+        if (hashdist)
+                return;
+
+        dentry_hashtable =
+                alloc_large_system_hash("Dentry cache",
+                                        sizeof(struct hlist_head),
+                                        dhash_entries,
+                                        13,
+                                        HASH_EARLY,
+                                        &d_hash_shift,
+                                        &d_hash_mask,
+                                        0);
+
+        for (loop = 0; loop < (1 << d_hash_shift); loop++)
+                INIT_HLIST_HEAD(&dentry_hashtable[loop]);
+}
+
+static void __init dcache_init(unsigned long mempages)
+{
+        int loop;
+
+        /* 
+         * A constructor could be added for stable state like the lists,
+         * but it is probably not worth it because of the cache nature
+         * of the dcache. 
+         */
+        dentry_cache = kmem_cache_create("dentry_cache",
+                                         sizeof(struct dentry),
+                                         0,
+                                         SLAB_RECLAIM_ACCOUNT|SLAB_PANIC,
+                                         NULL, NULL);
+        
+        set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
+
+        /* Hash may have been set up in dcache_init_early */
+        if (!hashdist)
+                return;
+
+        dentry_hashtable =
+                alloc_large_system_hash("Dentry cache",
+                                        sizeof(struct hlist_head),
+                                        dhash_entries,
+                                        13,
+                                        0,
+                                        &d_hash_shift,
+                                        &d_hash_mask,
+                                        0);
+
+        for (loop = 0; loop < (1 << d_hash_shift); loop++)
+                INIT_HLIST_HEAD(&dentry_hashtable[loop]);
+}
+
+/* SLAB cache for __getname() consumers */
+kmem_cache_t *names_cachep;
+
+/* SLAB cache for file structures */
+kmem_cache_t *filp_cachep;
+
+EXPORT_SYMBOL(d_genocide);
+
+extern void bdev_cache_init(void);
+extern void chrdev_init(void);
+
+void __init vfs_caches_init_early(void)
+{
+        dcache_init_early();
+        inode_init_early();
+}
+
+void __init vfs_caches_init(unsigned long mempages)
+{
+        unsigned long reserve;
+
+        /* Base hash sizes on available memory, with a reserve equal to
+           150% of current kernel size */
+
+        reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
+        mempages -= reserve;
+
+        names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
+                        SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+
+        filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
+                        SLAB_HWCACHE_ALIGN|SLAB_PANIC, filp_ctor, filp_dtor);
+
+        dcache_init(mempages);
+        inode_init(mempages);
+        files_init(mempages);
+        mnt_init(mempages);
+        bdev_cache_init();
+        chrdev_init();
+}
+
+EXPORT_SYMBOL(d_alloc);
+EXPORT_SYMBOL(d_alloc_anon);
+EXPORT_SYMBOL(d_alloc_root);
+EXPORT_SYMBOL(d_delete);
+EXPORT_SYMBOL(d_find_alias);
+EXPORT_SYMBOL(d_instantiate);
+EXPORT_SYMBOL(d_invalidate);
+EXPORT_SYMBOL(d_lookup);
+EXPORT_SYMBOL(d_move);
+EXPORT_SYMBOL(d_path);
+EXPORT_SYMBOL(d_prune_aliases);
+EXPORT_SYMBOL(d_rehash);
+EXPORT_SYMBOL(d_splice_alias);
+EXPORT_SYMBOL(d_validate);
+EXPORT_SYMBOL(dget_locked);
+EXPORT_SYMBOL(dput);
+EXPORT_SYMBOL(find_inode_number);
+EXPORT_SYMBOL(have_submounts);
+EXPORT_SYMBOL(names_cachep);
+EXPORT_SYMBOL(shrink_dcache_parent);
+EXPORT_SYMBOL(shrink_dcache_sb);