1 files changed, 1377 insertions, 0 deletions

diff --git a/fs/inode.c b/fs/inode.c
new file mode 100644
index 000000000000..af8fd78d2099
--- /dev/null
+++ b/fs/inode.c
@@ -0,0 +1,1377 @@
+/*
+ * linux/fs/inode.c
+ *
+ * (C) 1997 Linus Torvalds
+ */
+
+#include <linux/config.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/dcache.h>
+#include <linux/init.h>
+#include <linux/quotaops.h>
+#include <linux/slab.h>
+#include <linux/writeback.h>
+#include <linux/module.h>
+#include <linux/backing-dev.h>
+#include <linux/wait.h>
+#include <linux/hash.h>
+#include <linux/swap.h>
+#include <linux/security.h>
+#include <linux/pagemap.h>
+#include <linux/cdev.h>
+#include <linux/bootmem.h>
+
+/*
+ * This is needed for the following functions:
+ *  - inode_has_buffers
+ *  - invalidate_inode_buffers
+ *  - fsync_bdev
+ *  - invalidate_bdev
+ *
+ * FIXME: remove all knowledge of the buffer layer from this file
+ */
+#include <linux/buffer_head.h>
+
+/*
+ * New inode.c implementation.
+ *
+ * This implementation has the basic premise of trying
+ * to be extremely low-overhead and SMP-safe, yet be
+ * simple enough to be "obviously correct".
+ *
+ * Famous last words.
+ */
+
+/* inode dynamic allocation 1999, Andrea Arcangeli <andrea@suse.de> */
+
+/* #define INODE_PARANOIA 1 */
+/* #define INODE_DEBUG 1 */
+
+/*
+ * Inode lookup is no longer as critical as it used to be:
+ * most of the lookups are going to be through the dcache.
+ */
+#define I_HASHBITS      i_hash_shift
+#define I_HASHMASK      i_hash_mask
+
+static unsigned int i_hash_mask;
+static unsigned int i_hash_shift;
+
+/*
+ * Each inode can be on two separate lists. One is
+ * the hash list of the inode, used for lookups. The
+ * other linked list is the "type" list:
+ *  "in_use" - valid inode, i_count > 0, i_nlink > 0
+ *  "dirty"  - as "in_use" but also dirty
+ *  "unused" - valid inode, i_count = 0
+ *
+ * A "dirty" list is maintained for each super block,
+ * allowing for low-overhead inode sync() operations.
+ */
+
+LIST_HEAD(inode_in_use);
+LIST_HEAD(inode_unused);
+static struct hlist_head *inode_hashtable;
+
+/*
+ * A simple spinlock to protect the list manipulations.
+ *
+ * NOTE! You also have to own the lock if you change
+ * the i_state of an inode while it is in use..
+ */
+DEFINE_SPINLOCK(inode_lock);
+
+/*
+ * iprune_sem provides exclusion between the kswapd or try_to_free_pages
+ * icache shrinking path, and the umount path.  Without this exclusion,
+ * by the time prune_icache calls iput for the inode whose pages it has
+ * been invalidating, or by the time it calls clear_inode & destroy_inode
+ * from its final dispose_list, the struct super_block they refer to
+ * (for inode->i_sb->s_op) may already have been freed and reused.
+ */
+DECLARE_MUTEX(iprune_sem);
+
+/*
+ * Statistics gathering..
+ */
+struct inodes_stat_t inodes_stat;
+
+static kmem_cache_t * inode_cachep;
+
+static struct inode *alloc_inode(struct super_block *sb)
+{
+        static struct address_space_operations empty_aops;
+        static struct inode_operations empty_iops;
+        static struct file_operations empty_fops;
+        struct inode *inode;
+
+        if (sb->s_op->alloc_inode)
+                inode = sb->s_op->alloc_inode(sb);
+        else
+                inode = (struct inode *) kmem_cache_alloc(inode_cachep, SLAB_KERNEL);
+
+        if (inode) {
+                struct address_space * const mapping = &inode->i_data;
+
+                inode->i_sb = sb;
+                inode->i_blkbits = sb->s_blocksize_bits;
+                inode->i_flags = 0;
+                atomic_set(&inode->i_count, 1);
+                inode->i_op = &empty_iops;
+                inode->i_fop = &empty_fops;
+                inode->i_nlink = 1;
+                atomic_set(&inode->i_writecount, 0);
+                inode->i_size = 0;
+                inode->i_blocks = 0;
+                inode->i_bytes = 0;
+                inode->i_generation = 0;
+#ifdef CONFIG_QUOTA
+                memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
+#endif
+                inode->i_pipe = NULL;
+                inode->i_bdev = NULL;
+                inode->i_cdev = NULL;
+                inode->i_rdev = 0;
+                inode->i_security = NULL;
+                inode->dirtied_when = 0;
+                if (security_inode_alloc(inode)) {
+                        if (inode->i_sb->s_op->destroy_inode)
+                                inode->i_sb->s_op->destroy_inode(inode);
+                        else
+                                kmem_cache_free(inode_cachep, (inode));
+                        return NULL;
+                }
+
+                mapping->a_ops = &empty_aops;
+                mapping->host = inode;
+                mapping->flags = 0;
+                mapping_set_gfp_mask(mapping, GFP_HIGHUSER);
+                mapping->assoc_mapping = NULL;
+                mapping->backing_dev_info = &default_backing_dev_info;
+
+                /*
+                 * If the block_device provides a backing_dev_info for client
+                 * inodes then use that.  Otherwise the inode share the bdev's
+                 * backing_dev_info.
+                 */
+                if (sb->s_bdev) {
+                        struct backing_dev_info *bdi;
+
+                        bdi = sb->s_bdev->bd_inode_backing_dev_info;
+                        if (!bdi)
+                                bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
+                        mapping->backing_dev_info = bdi;
+                }
+                memset(&inode->u, 0, sizeof(inode->u));
+                inode->i_mapping = mapping;
+        }
+        return inode;
+}
+
+void destroy_inode(struct inode *inode) 
+{
+        if (inode_has_buffers(inode))
+                BUG();
+        security_inode_free(inode);
+        if (inode->i_sb->s_op->destroy_inode)
+                inode->i_sb->s_op->destroy_inode(inode);
+        else
+                kmem_cache_free(inode_cachep, (inode));
+}
+
+
+/*
+ * These are initializations that only need to be done
+ * once, because the fields are idempotent across use
+ * of the inode, so let the slab aware of that.
+ */
+void inode_init_once(struct inode *inode)
+{
+        memset(inode, 0, sizeof(*inode));
+        INIT_HLIST_NODE(&inode->i_hash);
+        INIT_LIST_HEAD(&inode->i_dentry);
+        INIT_LIST_HEAD(&inode->i_devices);
+        sema_init(&inode->i_sem, 1);
+        init_rwsem(&inode->i_alloc_sem);
+        INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
+        rwlock_init(&inode->i_data.tree_lock);
+        spin_lock_init(&inode->i_data.i_mmap_lock);
+        INIT_LIST_HEAD(&inode->i_data.private_list);
+        spin_lock_init(&inode->i_data.private_lock);
+        INIT_RAW_PRIO_TREE_ROOT(&inode->i_data.i_mmap);
+        INIT_LIST_HEAD(&inode->i_data.i_mmap_nonlinear);
+        spin_lock_init(&inode->i_lock);
+        i_size_ordered_init(inode);
+}
+
+EXPORT_SYMBOL(inode_init_once);
+
+static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
+{
+        struct inode * inode = (struct inode *) foo;
+
+        if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
+            SLAB_CTOR_CONSTRUCTOR)
+                inode_init_once(inode);
+}
+
+/*
+ * inode_lock must be held
+ */
+void __iget(struct inode * inode)
+{
+        if (atomic_read(&inode->i_count)) {
+                atomic_inc(&inode->i_count);
+                return;
+        }
+        atomic_inc(&inode->i_count);
+        if (!(inode->i_state & (I_DIRTY|I_LOCK)))
+                list_move(&inode->i_list, &inode_in_use);
+        inodes_stat.nr_unused--;
+}
+
+/**
+ * clear_inode - clear an inode
+ * @inode: inode to clear
+ *
+ * This is called by the filesystem to tell us
+ * that the inode is no longer useful. We just
+ * terminate it with extreme prejudice.
+ */
+void clear_inode(struct inode *inode)
+{
+        might_sleep();
+        invalidate_inode_buffers(inode);
+       
+        if (inode->i_data.nrpages)
+                BUG();
+        if (!(inode->i_state & I_FREEING))
+                BUG();
+        if (inode->i_state & I_CLEAR)
+                BUG();
+        wait_on_inode(inode);
+        DQUOT_DROP(inode);
+        if (inode->i_sb && inode->i_sb->s_op->clear_inode)
+                inode->i_sb->s_op->clear_inode(inode);
+        if (inode->i_bdev)
+                bd_forget(inode);
+        if (inode->i_cdev)
+                cd_forget(inode);
+        inode->i_state = I_CLEAR;
+}
+
+EXPORT_SYMBOL(clear_inode);
+
+/*
+ * dispose_list - dispose of the contents of a local list
+ * @head: the head of the list to free
+ *
+ * Dispose-list gets a local list with local inodes in it, so it doesn't
+ * need to worry about list corruption and SMP locks.
+ */
+static void dispose_list(struct list_head *head)
+{
+        int nr_disposed = 0;
+
+        while (!list_empty(head)) {
+                struct inode *inode;
+
+                inode = list_entry(head->next, struct inode, i_list);
+                list_del(&inode->i_list);
+
+                if (inode->i_data.nrpages)
+                        truncate_inode_pages(&inode->i_data, 0);
+                clear_inode(inode);
+                destroy_inode(inode);
+                nr_disposed++;
+        }
+        spin_lock(&inode_lock);
+        inodes_stat.nr_inodes -= nr_disposed;
+        spin_unlock(&inode_lock);
+}
+
+/*
+ * Invalidate all inodes for a device.
+ */
+static int invalidate_list(struct list_head *head, struct list_head *dispose)
+{
+        struct list_head *next;
+        int busy = 0, count = 0;
+
+        next = head->next;
+        for (;;) {
+                struct list_head * tmp = next;
+                struct inode * inode;
+
+                /*
+                 * We can reschedule here without worrying about the list's
+                 * consistency because the per-sb list of inodes must not
+                 * change during umount anymore, and because iprune_sem keeps
+                 * shrink_icache_memory() away.
+                 */
+                cond_resched_lock(&inode_lock);
+
+                next = next->next;
+                if (tmp == head)
+                        break;
+                inode = list_entry(tmp, struct inode, i_sb_list);
+                invalidate_inode_buffers(inode);
+                if (!atomic_read(&inode->i_count)) {
+                        hlist_del_init(&inode->i_hash);
+                        list_del(&inode->i_sb_list);
+                        list_move(&inode->i_list, dispose);
+                        inode->i_state |= I_FREEING;
+                        count++;
+                        continue;
+                }
+                busy = 1;
+        }
+        /* only unused inodes may be cached with i_count zero */
+        inodes_stat.nr_unused -= count;
+        return busy;
+}
+
+/*
+ * This is a two-stage process. First we collect all
+ * offending inodes onto the throw-away list, and in
+ * the second stage we actually dispose of them. This
+ * is because we don't want to sleep while messing
+ * with the global lists..
+ */
+ 
+/**
+ *      invalidate_inodes       - discard the inodes on a device
+ *      @sb: superblock
+ *
+ *      Discard all of the inodes for a given superblock. If the discard
+ *      fails because there are busy inodes then a non zero value is returned.
+ *      If the discard is successful all the inodes have been discarded.
+ */
+int invalidate_inodes(struct super_block * sb)
+{
+        int busy;
+        LIST_HEAD(throw_away);
+
+        down(&iprune_sem);
+        spin_lock(&inode_lock);
+        busy = invalidate_list(&sb->s_inodes, &throw_away);
+        spin_unlock(&inode_lock);
+
+        dispose_list(&throw_away);
+        up(&iprune_sem);
+
+        return busy;
+}
+
+EXPORT_SYMBOL(invalidate_inodes);
+ 
+int __invalidate_device(struct block_device *bdev, int do_sync)
+{
+        struct super_block *sb;
+        int res;
+
+        if (do_sync)
+                fsync_bdev(bdev);
+
+        res = 0;
+        sb = get_super(bdev);
+        if (sb) {
+                /*
+                 * no need to lock the super, get_super holds the
+                 * read semaphore so the filesystem cannot go away
+                 * under us (->put_super runs with the write lock
+                 * hold).
+                 */
+                shrink_dcache_sb(sb);
+                res = invalidate_inodes(sb);
+                drop_super(sb);
+        }
+        invalidate_bdev(bdev, 0);
+        return res;
+}
+
+EXPORT_SYMBOL(__invalidate_device);
+
+static int can_unuse(struct inode *inode)
+{
+        if (inode->i_state)
+                return 0;
+        if (inode_has_buffers(inode))
+                return 0;
+        if (atomic_read(&inode->i_count))
+                return 0;
+        if (inode->i_data.nrpages)
+                return 0;
+        return 1;
+}
+
+/*
+ * Scan `goal' inodes on the unused list for freeable ones. They are moved to
+ * a temporary list and then are freed outside inode_lock by dispose_list().
+ *
+ * Any inodes which are pinned purely because of attached pagecache have their
+ * pagecache removed.  We expect the final iput() on that inode to add it to
+ * the front of the inode_unused list.  So look for it there and if the
+ * inode is still freeable, proceed.  The right inode is found 99.9% of the
+ * time in testing on a 4-way.
+ *
+ * If the inode has metadata buffers attached to mapping->private_list then
+ * try to remove them.
+ */
+static void prune_icache(int nr_to_scan)
+{
+        LIST_HEAD(freeable);
+        int nr_pruned = 0;
+        int nr_scanned;
+        unsigned long reap = 0;
+
+        down(&iprune_sem);
+        spin_lock(&inode_lock);
+        for (nr_scanned = 0; nr_scanned < nr_to_scan; nr_scanned++) {
+                struct inode *inode;
+
+                if (list_empty(&inode_unused))
+                        break;
+
+                inode = list_entry(inode_unused.prev, struct inode, i_list);
+
+                if (inode->i_state || atomic_read(&inode->i_count)) {
+                        list_move(&inode->i_list, &inode_unused);
+                        continue;
+                }
+                if (inode_has_buffers(inode) || inode->i_data.nrpages) {
+                        __iget(inode);
+                        spin_unlock(&inode_lock);
+                        if (remove_inode_buffers(inode))
+                                reap += invalidate_inode_pages(&inode->i_data);
+                        iput(inode);
+                        spin_lock(&inode_lock);
+
+                        if (inode != list_entry(inode_unused.next,
+                                                struct inode, i_list))
+                                continue;       /* wrong inode or list_empty */
+                        if (!can_unuse(inode))
+                                continue;
+                }
+                hlist_del_init(&inode->i_hash);
+                list_del_init(&inode->i_sb_list);
+                list_move(&inode->i_list, &freeable);
+                inode->i_state |= I_FREEING;
+                nr_pruned++;
+        }
+        inodes_stat.nr_unused -= nr_pruned;
+        spin_unlock(&inode_lock);
+
+        dispose_list(&freeable);
+        up(&iprune_sem);
+
+        if (current_is_kswapd())
+                mod_page_state(kswapd_inodesteal, reap);
+        else
+                mod_page_state(pginodesteal, reap);
+}
+
+/*
+ * shrink_icache_memory() will attempt to reclaim some unused inodes.  Here,
+ * "unused" means that no dentries are referring to the inodes: the files are
+ * not open and the dcache references to those inodes have already been
+ * reclaimed.
+ *
+ * This function is passed the number of inodes to scan, and it returns the
+ * total number of remaining possibly-reclaimable inodes.
+ */
+static int shrink_icache_memory(int nr, unsigned int gfp_mask)
+{
+        if (nr) {
+                /*
+                 * Nasty deadlock avoidance.  We may hold various FS locks,
+                 * and we don't want to recurse into the FS that called us
+                 * in clear_inode() and friends..
+                 */
+                if (!(gfp_mask & __GFP_FS))
+                        return -1;
+                prune_icache(nr);
+        }
+        return (inodes_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
+}
+
+static void __wait_on_freeing_inode(struct inode *inode);
+/*
+ * Called with the inode lock held.
+ * NOTE: we are not increasing the inode-refcount, you must call __iget()
+ * by hand after calling find_inode now! This simplifies iunique and won't
+ * add any additional branch in the common code.
+ */
+static struct inode * find_inode(struct super_block * sb, struct hlist_head *head, int (*test)(struct inode *, void *), void *data)
+{
+        struct hlist_node *node;
+        struct inode * inode = NULL;
+
+repeat:
+        hlist_for_each (node, head) { 
+                inode = hlist_entry(node, struct inode, i_hash);
+                if (inode->i_sb != sb)
+                        continue;
+                if (!test(inode, data))
+                        continue;
+                if (inode->i_state & (I_FREEING|I_CLEAR)) {
+                        __wait_on_freeing_inode(inode);
+                        goto repeat;
+                }
+                break;
+        }
+        return node ? inode : NULL;
+}
+
+/*
+ * find_inode_fast is the fast path version of find_inode, see the comment at
+ * iget_locked for details.
+ */
+static struct inode * find_inode_fast(struct super_block * sb, struct hlist_head *head, unsigned long ino)
+{
+        struct hlist_node *node;
+        struct inode * inode = NULL;
+
+repeat:
+        hlist_for_each (node, head) {
+                inode = hlist_entry(node, struct inode, i_hash);
+                if (inode->i_ino != ino)
+                        continue;
+                if (inode->i_sb != sb)
+                        continue;
+                if (inode->i_state & (I_FREEING|I_CLEAR)) {
+                        __wait_on_freeing_inode(inode);
+                        goto repeat;
+                }
+                break;
+        }
+        return node ? inode : NULL;
+}
+
+/**
+ *      new_inode       - obtain an inode
+ *      @sb: superblock
+ *
+ *      Allocates a new inode for given superblock.
+ */
+struct inode *new_inode(struct super_block *sb)
+{
+        static unsigned long last_ino;
+        struct inode * inode;
+
+        spin_lock_prefetch(&inode_lock);
+        
+        inode = alloc_inode(sb);
+        if (inode) {
+                spin_lock(&inode_lock);
+                inodes_stat.nr_inodes++;
+                list_add(&inode->i_list, &inode_in_use);
+                list_add(&inode->i_sb_list, &sb->s_inodes);
+                inode->i_ino = ++last_ino;
+                inode->i_state = 0;
+                spin_unlock(&inode_lock);
+        }
+        return inode;
+}
+
+EXPORT_SYMBOL(new_inode);
+
+void unlock_new_inode(struct inode *inode)
+{
+        /*
+         * This is special!  We do not need the spinlock
+         * when clearing I_LOCK, because we're guaranteed
+         * that nobody else tries to do anything about the
+         * state of the inode when it is locked, as we
+         * just created it (so there can be no old holders
+         * that haven't tested I_LOCK).
+         */
+        inode->i_state &= ~(I_LOCK|I_NEW);
+        wake_up_inode(inode);
+}
+
+EXPORT_SYMBOL(unlock_new_inode);
+
+/*
+ * This is called without the inode lock held.. Be careful.
+ *
+ * We no longer cache the sb_flags in i_flags - see fs.h
+ *      -- rmk@arm.uk.linux.org
+ */
+static struct inode * get_new_inode(struct super_block *sb, struct hlist_head *head, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *data)
+{
+        struct inode * inode;
+
+        inode = alloc_inode(sb);
+        if (inode) {
+                struct inode * old;
+
+                spin_lock(&inode_lock);
+                /* We released the lock, so.. */
+                old = find_inode(sb, head, test, data);
+                if (!old) {
+                        if (set(inode, data))
+                                goto set_failed;
+
+                        inodes_stat.nr_inodes++;
+                        list_add(&inode->i_list, &inode_in_use);
+                        list_add(&inode->i_sb_list, &sb->s_inodes);
+                        hlist_add_head(&inode->i_hash, head);
+                        inode->i_state = I_LOCK|I_NEW;
+                        spin_unlock(&inode_lock);
+
+                        /* Return the locked inode with I_NEW set, the
+                         * caller is responsible for filling in the contents
+                         */
+                        return inode;
+                }
+
+                /*
+                 * Uhhuh, somebody else created the same inode under
+                 * us. Use the old inode instead of the one we just
+                 * allocated.
+                 */
+                __iget(old);
+                spin_unlock(&inode_lock);
+                destroy_inode(inode);
+                inode = old;
+                wait_on_inode(inode);
+        }
+        return inode;
+
+set_failed:
+        spin_unlock(&inode_lock);
+        destroy_inode(inode);
+        return NULL;
+}
+
+/*
+ * get_new_inode_fast is the fast path version of get_new_inode, see the
+ * comment at iget_locked for details.
+ */
+static struct inode * get_new_inode_fast(struct super_block *sb, struct hlist_head *head, unsigned long ino)
+{
+        struct inode * inode;
+
+        inode = alloc_inode(sb);
+        if (inode) {
+                struct inode * old;
+
+                spin_lock(&inode_lock);
+                /* We released the lock, so.. */
+                old = find_inode_fast(sb, head, ino);
+                if (!old) {
+                        inode->i_ino = ino;
+                        inodes_stat.nr_inodes++;
+                        list_add(&inode->i_list, &inode_in_use);
+                        list_add(&inode->i_sb_list, &sb->s_inodes);
+                        hlist_add_head(&inode->i_hash, head);
+                        inode->i_state = I_LOCK|I_NEW;
+                        spin_unlock(&inode_lock);
+
+                        /* Return the locked inode with I_NEW set, the
+                         * caller is responsible for filling in the contents
+                         */
+                        return inode;
+                }
+
+                /*
+                 * Uhhuh, somebody else created the same inode under
+                 * us. Use the old inode instead of the one we just
+                 * allocated.
+                 */
+                __iget(old);
+                spin_unlock(&inode_lock);
+                destroy_inode(inode);
+                inode = old;
+                wait_on_inode(inode);
+        }
+        return inode;
+}
+
+static inline unsigned long hash(struct super_block *sb, unsigned long hashval)
+{
+        unsigned long tmp;
+
+        tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
+                        L1_CACHE_BYTES;
+        tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS);
+        return tmp & I_HASHMASK;
+}
+
+/**
+ *      iunique - get a unique inode number
+ *      @sb: superblock
+ *      @max_reserved: highest reserved inode number
+ *
+ *      Obtain an inode number that is unique on the system for a given
+ *      superblock. This is used by file systems that have no natural
+ *      permanent inode numbering system. An inode number is returned that
+ *      is higher than the reserved limit but unique.
+ *
+ *      BUGS:
+ *      With a large number of inodes live on the file system this function
+ *      currently becomes quite slow.
+ */
+ino_t iunique(struct super_block *sb, ino_t max_reserved)
+{
+        static ino_t counter;
+        struct inode *inode;
+        struct hlist_head * head;
+        ino_t res;
+        spin_lock(&inode_lock);
+retry:
+        if (counter > max_reserved) {
+                head = inode_hashtable + hash(sb,counter);
+                res = counter++;
+                inode = find_inode_fast(sb, head, res);
+                if (!inode) {
+                        spin_unlock(&inode_lock);
+                        return res;
+                }
+        } else {
+                counter = max_reserved + 1;
+        }
+        goto retry;
+        
+}
+
+EXPORT_SYMBOL(iunique);
+
+struct inode *igrab(struct inode *inode)
+{
+        spin_lock(&inode_lock);
+        if (!(inode->i_state & I_FREEING))
+                __iget(inode);
+        else
+                /*
+                 * Handle the case where s_op->clear_inode is not been
+                 * called yet, and somebody is calling igrab
+                 * while the inode is getting freed.
+                 */
+                inode = NULL;
+        spin_unlock(&inode_lock);
+        return inode;
+}
+
+EXPORT_SYMBOL(igrab);
+
+/**
+ * ifind - internal function, you want ilookup5() or iget5().
+ * @sb:         super block of file system to search
+ * @head:       the head of the list to search
+ * @test:       callback used for comparisons between inodes
+ * @data:       opaque data pointer to pass to @test
+ *
+ * ifind() searches for the inode specified by @data in the inode
+ * cache. This is a generalized version of ifind_fast() for file systems where
+ * the inode number is not sufficient for unique identification of an inode.
+ *
+ * If the inode is in the cache, the inode is returned with an incremented
+ * reference count.
+ *
+ * Otherwise NULL is returned.
+ *
+ * Note, @test is called with the inode_lock held, so can't sleep.
+ */
+static inline struct inode *ifind(struct super_block *sb,
+                struct hlist_head *head, int (*test)(struct inode *, void *),
+                void *data)
+{
+        struct inode *inode;
+
+        spin_lock(&inode_lock);
+        inode = find_inode(sb, head, test, data);
+        if (inode) {
+                __iget(inode);
+                spin_unlock(&inode_lock);
+                wait_on_inode(inode);
+                return inode;
+        }
+        spin_unlock(&inode_lock);
+        return NULL;
+}
+
+/**
+ * ifind_fast - internal function, you want ilookup() or iget().
+ * @sb:         super block of file system to search
+ * @head:       head of the list to search
+ * @ino:        inode number to search for
+ *
+ * ifind_fast() searches for the inode @ino in the inode cache. This is for
+ * file systems where the inode number is sufficient for unique identification
+ * of an inode.
+ *
+ * If the inode is in the cache, the inode is returned with an incremented
+ * reference count.
+ *
+ * Otherwise NULL is returned.
+ */
+static inline struct inode *ifind_fast(struct super_block *sb,
+                struct hlist_head *head, unsigned long ino)
+{
+        struct inode *inode;
+
+        spin_lock(&inode_lock);
+        inode = find_inode_fast(sb, head, ino);
+        if (inode) {
+                __iget(inode);
+                spin_unlock(&inode_lock);
+                wait_on_inode(inode);
+                return inode;
+        }
+        spin_unlock(&inode_lock);
+        return NULL;
+}
+
+/**
+ * ilookup5 - search for an inode in the inode cache
+ * @sb:         super block of file system to search
+ * @hashval:    hash value (usually inode number) to search for
+ * @test:       callback used for comparisons between inodes
+ * @data:       opaque data pointer to pass to @test
+ *
+ * ilookup5() uses ifind() to search for the inode specified by @hashval and
+ * @data in the inode cache. This is a generalized version of ilookup() for
+ * file systems where the inode number is not sufficient for unique
+ * identification of an inode.
+ *
+ * If the inode is in the cache, the inode is returned with an incremented
+ * reference count.
+ *
+ * Otherwise NULL is returned.
+ *
+ * Note, @test is called with the inode_lock held, so can't sleep.
+ */
+struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
+                int (*test)(struct inode *, void *), void *data)
+{
+        struct hlist_head *head = inode_hashtable + hash(sb, hashval);
+
+        return ifind(sb, head, test, data);
+}
+
+EXPORT_SYMBOL(ilookup5);
+
+/**
+ * ilookup - search for an inode in the inode cache
+ * @sb:         super block of file system to search
+ * @ino:        inode number to search for
+ *
+ * ilookup() uses ifind_fast() to search for the inode @ino in the inode cache.
+ * This is for file systems where the inode number is sufficient for unique
+ * identification of an inode.
+ *
+ * If the inode is in the cache, the inode is returned with an incremented
+ * reference count.
+ *
+ * Otherwise NULL is returned.
+ */
+struct inode *ilookup(struct super_block *sb, unsigned long ino)
+{
+        struct hlist_head *head = inode_hashtable + hash(sb, ino);
+
+        return ifind_fast(sb, head, ino);
+}
+
+EXPORT_SYMBOL(ilookup);
+
+/**
+ * iget5_locked - obtain an inode from a mounted file system
+ * @sb:         super block of file system
+ * @hashval:    hash value (usually inode number) to get
+ * @test:       callback used for comparisons between inodes
+ * @set:        callback used to initialize a new struct inode
+ * @data:       opaque data pointer to pass to @test and @set
+ *
+ * This is iget() without the read_inode() portion of get_new_inode().
+ *
+ * iget5_locked() uses ifind() to search for the inode specified by @hashval
+ * and @data in the inode cache and if present it is returned with an increased
+ * reference count. This is a generalized version of iget_locked() for file
+ * systems where the inode number is not sufficient for unique identification
+ * of an inode.
+ *
+ * If the inode is not in cache, get_new_inode() is called to allocate a new
+ * inode and this is returned locked, hashed, and with the I_NEW flag set. The
+ * file system gets to fill it in before unlocking it via unlock_new_inode().
+ *
+ * Note both @test and @set are called with the inode_lock held, so can't sleep.
+ */
+struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
+                int (*test)(struct inode *, void *),
+                int (*set)(struct inode *, void *), void *data)
+{
+        struct hlist_head *head = inode_hashtable + hash(sb, hashval);
+        struct inode *inode;
+
+        inode = ifind(sb, head, test, data);
+        if (inode)
+                return inode;
+        /*
+         * get_new_inode() will do the right thing, re-trying the search
+         * in case it had to block at any point.
+         */
+        return get_new_inode(sb, head, test, set, data);
+}
+
+EXPORT_SYMBOL(iget5_locked);
+
+/**
+ * iget_locked - obtain an inode from a mounted file system
+ * @sb:         super block of file system
+ * @ino:        inode number to get
+ *
+ * This is iget() without the read_inode() portion of get_new_inode_fast().
+ *
+ * iget_locked() uses ifind_fast() to search for the inode specified by @ino in
+ * the inode cache and if present it is returned with an increased reference
+ * count. This is for file systems where the inode number is sufficient for
+ * unique identification of an inode.
+ *
+ * If the inode is not in cache, get_new_inode_fast() is called to allocate a
+ * new inode and this is returned locked, hashed, and with the I_NEW flag set.
+ * The file system gets to fill it in before unlocking it via
+ * unlock_new_inode().
+ */
+struct inode *iget_locked(struct super_block *sb, unsigned long ino)
+{
+        struct hlist_head *head = inode_hashtable + hash(sb, ino);
+        struct inode *inode;
+
+        inode = ifind_fast(sb, head, ino);
+        if (inode)
+                return inode;
+        /*
+         * get_new_inode_fast() will do the right thing, re-trying the search
+         * in case it had to block at any point.
+         */
+        return get_new_inode_fast(sb, head, ino);
+}
+
+EXPORT_SYMBOL(iget_locked);
+
+/**
+ *      __insert_inode_hash - hash an inode
+ *      @inode: unhashed inode
+ *      @hashval: unsigned long value used to locate this object in the
+ *              inode_hashtable.
+ *
+ *      Add an inode to the inode hash for this superblock.
+ */
+void __insert_inode_hash(struct inode *inode, unsigned long hashval)
+{
+        struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
+        spin_lock(&inode_lock);
+        hlist_add_head(&inode->i_hash, head);
+        spin_unlock(&inode_lock);
+}
+
+EXPORT_SYMBOL(__insert_inode_hash);
+
+/**
+ *      remove_inode_hash - remove an inode from the hash
+ *      @inode: inode to unhash
+ *
+ *      Remove an inode from the superblock.
+ */
+void remove_inode_hash(struct inode *inode)
+{
+        spin_lock(&inode_lock);
+        hlist_del_init(&inode->i_hash);
+        spin_unlock(&inode_lock);
+}
+
+EXPORT_SYMBOL(remove_inode_hash);
+
+/*
+ * Tell the filesystem that this inode is no longer of any interest and should
+ * be completely destroyed.
+ *
+ * We leave the inode in the inode hash table until *after* the filesystem's
+ * ->delete_inode completes.  This ensures that an iget (such as nfsd might
+ * instigate) will always find up-to-date information either in the hash or on
+ * disk.
+ *
+ * I_FREEING is set so that no-one will take a new reference to the inode while
+ * it is being deleted.
+ */
+void generic_delete_inode(struct inode *inode)
+{
+        struct super_operations *op = inode->i_sb->s_op;
+
+        list_del_init(&inode->i_list);
+        list_del_init(&inode->i_sb_list);
+        inode->i_state|=I_FREEING;
+        inodes_stat.nr_inodes--;
+        spin_unlock(&inode_lock);
+
+        if (inode->i_data.nrpages)
+                truncate_inode_pages(&inode->i_data, 0);
+
+        security_inode_delete(inode);
+
+        if (op->delete_inode) {
+                void (*delete)(struct inode *) = op->delete_inode;
+                if (!is_bad_inode(inode))
+                        DQUOT_INIT(inode);
+                /* s_op->delete_inode internally recalls clear_inode() */
+                delete(inode);
+        } else
+                clear_inode(inode);
+        spin_lock(&inode_lock);
+        hlist_del_init(&inode->i_hash);
+        spin_unlock(&inode_lock);
+        wake_up_inode(inode);
+        if (inode->i_state != I_CLEAR)
+                BUG();
+        destroy_inode(inode);
+}
+
+EXPORT_SYMBOL(generic_delete_inode);
+
+static void generic_forget_inode(struct inode *inode)
+{
+        struct super_block *sb = inode->i_sb;
+
+        if (!hlist_unhashed(&inode->i_hash)) {
+                if (!(inode->i_state & (I_DIRTY|I_LOCK)))
+                        list_move(&inode->i_list, &inode_unused);
+                inodes_stat.nr_unused++;
+                spin_unlock(&inode_lock);
+                if (!sb || (sb->s_flags & MS_ACTIVE))
+                        return;
+                write_inode_now(inode, 1);
+                spin_lock(&inode_lock);
+                inodes_stat.nr_unused--;
+                hlist_del_init(&inode->i_hash);
+        }
+        list_del_init(&inode->i_list);
+        list_del_init(&inode->i_sb_list);
+        inode->i_state|=I_FREEING;
+        inodes_stat.nr_inodes--;
+        spin_unlock(&inode_lock);
+        if (inode->i_data.nrpages)
+                truncate_inode_pages(&inode->i_data, 0);
+        clear_inode(inode);
+        destroy_inode(inode);
+}
+
+/*
+ * Normal UNIX filesystem behaviour: delete the
+ * inode when the usage count drops to zero, and
+ * i_nlink is zero.
+ */
+static void generic_drop_inode(struct inode *inode)
+{
+        if (!inode->i_nlink)
+                generic_delete_inode(inode);
+        else
+                generic_forget_inode(inode);
+}
+
+/*
+ * Called when we're dropping the last reference
+ * to an inode. 
+ *
+ * Call the FS "drop()" function, defaulting to
+ * the legacy UNIX filesystem behaviour..
+ *
+ * NOTE! NOTE! NOTE! We're called with the inode lock
+ * held, and the drop function is supposed to release
+ * the lock!
+ */
+static inline void iput_final(struct inode *inode)
+{
+        struct super_operations *op = inode->i_sb->s_op;
+        void (*drop)(struct inode *) = generic_drop_inode;
+
+        if (op && op->drop_inode)
+                drop = op->drop_inode;
+        drop(inode);
+}
+
+/**
+ *      iput    - put an inode 
+ *      @inode: inode to put
+ *
+ *      Puts an inode, dropping its usage count. If the inode use count hits
+ *      zero, the inode is then freed and may also be destroyed.
+ *
+ *      Consequently, iput() can sleep.
+ */
+void iput(struct inode *inode)
+{
+        if (inode) {
+                struct super_operations *op = inode->i_sb->s_op;
+
+                BUG_ON(inode->i_state == I_CLEAR);
+
+                if (op && op->put_inode)
+                        op->put_inode(inode);
+
+                if (atomic_dec_and_lock(&inode->i_count, &inode_lock))
+                        iput_final(inode);
+        }
+}
+
+EXPORT_SYMBOL(iput);
+
+/**
+ *      bmap    - find a block number in a file
+ *      @inode: inode of file
+ *      @block: block to find
+ *
+ *      Returns the block number on the device holding the inode that
+ *      is the disk block number for the block of the file requested.
+ *      That is, asked for block 4 of inode 1 the function will return the
+ *      disk block relative to the disk start that holds that block of the 
+ *      file.
+ */
+sector_t bmap(struct inode * inode, sector_t block)
+{
+        sector_t res = 0;
+        if (inode->i_mapping->a_ops->bmap)
+                res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
+        return res;
+}
+
+EXPORT_SYMBOL(bmap);
+
+/**
+ *      update_atime    -       update the access time
+ *      @inode: inode accessed
+ *
+ *      Update the accessed time on an inode and mark it for writeback.
+ *      This function automatically handles read only file systems and media,
+ *      as well as the "noatime" flag and inode specific "noatime" markers.
+ */
+void update_atime(struct inode *inode)
+{
+        struct timespec now;
+
+        if (IS_NOATIME(inode))
+                return;
+        if (IS_NODIRATIME(inode) && S_ISDIR(inode->i_mode))
+                return;
+        if (IS_RDONLY(inode))
+                return;
+
+        now = current_fs_time(inode->i_sb);
+        if (!timespec_equal(&inode->i_atime, &now)) {
+                inode->i_atime = now;
+                mark_inode_dirty_sync(inode);
+        } else {
+                if (!timespec_equal(&inode->i_atime, &now))
+                        inode->i_atime = now;
+        }
+}
+
+EXPORT_SYMBOL(update_atime);
+
+/**
+ *      inode_update_time       -       update mtime and ctime time
+ *      @inode: inode accessed
+ *      @ctime_too: update ctime too
+ *
+ *      Update the mtime time on an inode and mark it for writeback.
+ *      When ctime_too is specified update the ctime too.
+ */
+
+void inode_update_time(struct inode *inode, int ctime_too)
+{
+        struct timespec now;
+        int sync_it = 0;
+
+        if (IS_NOCMTIME(inode))
+                return;
+        if (IS_RDONLY(inode))
+                return;
+
+        now = current_fs_time(inode->i_sb);
+        if (!timespec_equal(&inode->i_mtime, &now))
+                sync_it = 1;
+        inode->i_mtime = now;
+
+        if (ctime_too) {
+                if (!timespec_equal(&inode->i_ctime, &now))
+                        sync_it = 1;
+                inode->i_ctime = now;
+        }
+        if (sync_it)
+                mark_inode_dirty_sync(inode);
+}
+
+EXPORT_SYMBOL(inode_update_time);
+
+int inode_needs_sync(struct inode *inode)
+{
+        if (IS_SYNC(inode))
+                return 1;
+        if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
+                return 1;
+        return 0;
+}
+
+EXPORT_SYMBOL(inode_needs_sync);
+
+/*
+ *      Quota functions that want to walk the inode lists..
+ */
+#ifdef CONFIG_QUOTA
+
+/* Function back in dquot.c */
+int remove_inode_dquot_ref(struct inode *, int, struct list_head *);
+
+void remove_dquot_ref(struct super_block *sb, int type,
+                        struct list_head *tofree_head)
+{
+        struct inode *inode;
+
+        if (!sb->dq_op)
+                return; /* nothing to do */
+        spin_lock(&inode_lock); /* This lock is for inodes code */
+
+        /*
+         * We don't have to lock against quota code - test IS_QUOTAINIT is
+         * just for speedup...
+         */
+        list_for_each_entry(inode, &sb->s_inodes, i_sb_list)
+                if (!IS_NOQUOTA(inode))
+                        remove_inode_dquot_ref(inode, type, tofree_head);
+
+        spin_unlock(&inode_lock);
+}
+
+#endif
+
+int inode_wait(void *word)
+{
+        schedule();
+        return 0;
+}
+
+/*
+ * If we try to find an inode in the inode hash while it is being deleted, we
+ * have to wait until the filesystem completes its deletion before reporting
+ * that it isn't found.  This is because iget will immediately call
+ * ->read_inode, and we want to be sure that evidence of the deletion is found
+ * by ->read_inode.
+ * This is called with inode_lock held.
+ */
+static void __wait_on_freeing_inode(struct inode *inode)
+{
+        wait_queue_head_t *wq;
+        DEFINE_WAIT_BIT(wait, &inode->i_state, __I_LOCK);
+
+        /*
+         * I_FREEING and I_CLEAR are cleared in process context under
+         * inode_lock, so we have to give the tasks who would clear them
+         * a chance to run and acquire inode_lock.
+         */
+        if (!(inode->i_state & I_LOCK)) {
+                spin_unlock(&inode_lock);
+                yield();
+                spin_lock(&inode_lock);
+                return;
+        }
+        wq = bit_waitqueue(&inode->i_state, __I_LOCK);
+        prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
+        spin_unlock(&inode_lock);
+        schedule();
+        finish_wait(wq, &wait.wait);
+        spin_lock(&inode_lock);
+}
+
+void wake_up_inode(struct inode *inode)
+{
+        /*
+         * Prevent speculative execution through spin_unlock(&inode_lock);
+         */
+        smp_mb();
+        wake_up_bit(&inode->i_state, __I_LOCK);
+}
+
+static __initdata unsigned long ihash_entries;
+static int __init set_ihash_entries(char *str)
+{
+        if (!str)
+                return 0;
+        ihash_entries = simple_strtoul(str, &str, 0);
+        return 1;
+}
+__setup("ihash_entries=", set_ihash_entries);
+
+/*
+ * Initialize the waitqueues and inode hash table.
+ */
+void __init inode_init_early(void)
+{
+        int loop;
+
+        /* If hashes are distributed across NUMA nodes, defer
+         * hash allocation until vmalloc space is available.
+         */
+        if (hashdist)
+                return;
+
+        inode_hashtable =
+                alloc_large_system_hash("Inode-cache",
+                                        sizeof(struct hlist_head),
+                                        ihash_entries,
+                                        14,
+                                        HASH_EARLY,
+                                        &i_hash_shift,
+                                        &i_hash_mask,
+                                        0);
+
+        for (loop = 0; loop < (1 << i_hash_shift); loop++)
+                INIT_HLIST_HEAD(&inode_hashtable[loop]);
+}
+
+void __init inode_init(unsigned long mempages)
+{
+        int loop;
+
+        /* inode slab cache */
+        inode_cachep = kmem_cache_create("inode_cache", sizeof(struct inode),
+                                0, SLAB_PANIC, init_once, NULL);
+        set_shrinker(DEFAULT_SEEKS, shrink_icache_memory);
+
+        /* Hash may have been set up in inode_init_early */
+        if (!hashdist)
+                return;
+
+        inode_hashtable =
+                alloc_large_system_hash("Inode-cache",
+                                        sizeof(struct hlist_head),
+                                        ihash_entries,
+                                        14,
+                                        0,
+                                        &i_hash_shift,
+                                        &i_hash_mask,
+                                        0);
+
+        for (loop = 0; loop < (1 << i_hash_shift); loop++)
+                INIT_HLIST_HEAD(&inode_hashtable[loop]);
+}
+
+void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
+{
+        inode->i_mode = mode;
+        if (S_ISCHR(mode)) {
+                inode->i_fop = &def_chr_fops;
+                inode->i_rdev = rdev;
+        } else if (S_ISBLK(mode)) {
+                inode->i_fop = &def_blk_fops;
+                inode->i_rdev = rdev;
+        } else if (S_ISFIFO(mode))
+                inode->i_fop = &def_fifo_fops;
+        else if (S_ISSOCK(mode))
+                inode->i_fop = &bad_sock_fops;
+        else
+                printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o)\n",
+                       mode);
+}
+EXPORT_SYMBOL(init_special_inode);