Logo Search packages:      
Sourcecode: linux version File versions  Download package

inode.c

/*
 * linux/fs/inode.c
 *
 * (C) 1997 Linus Torvalds
 */

#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>
#include <linux/inotify.h>
#include <linux/mount.h>

/*
 * This is needed for the following functions:
 *  - inode_has_buffers
 *  - invalidate_inode_buffers
 *  - 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 __read_mostly;
static unsigned int i_hash_shift __read_mostly;

/*
 * 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 __read_mostly;

/*
 * 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_mutex 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.
 */
static DEFINE_MUTEX(iprune_mutex);

/*
 * Statistics gathering..
 */
struct inodes_stat_t inodes_stat;

static struct kmem_cache * inode_cachep __read_mostly;

static 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 struct inode *alloc_inode(struct super_block *sb)
{
      static const struct address_space_operations empty_aops;
      static struct inode_operations empty_iops;
      static const 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, GFP_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->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;
            }

            spin_lock_init(&inode->i_lock);
            lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);

            mutex_init(&inode->i_mutex);
            lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);

            init_rwsem(&inode->i_alloc_sem);
            lockdep_set_class(&inode->i_alloc_sem, &sb->s_type->i_alloc_sem_key);

            mapping->a_ops = &empty_aops;
            mapping->host = inode;
            mapping->flags = 0;
            mapping_set_gfp_mask(mapping, GFP_HIGHUSER_PAGECACHE);
            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;
            }
            inode->i_private = NULL;
            inode->i_mapping = mapping;
      }
      return inode;
}

void destroy_inode(struct inode *inode) 
{
      BUG_ON(inode_has_buffers(inode));
      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);
      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);
      i_size_ordered_init(inode);
#ifdef CONFIG_INOTIFY
      INIT_LIST_HEAD(&inode->inotify_watches);
      mutex_init(&inode->inotify_mutex);
#endif
}

EXPORT_SYMBOL(inode_init_once);

static void init_once(struct kmem_cache * cachep, void *foo)
{
      struct inode * inode = (struct inode *) foo;

      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_SYNC)))
            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);
       
      BUG_ON(inode->i_data.nrpages);
      BUG_ON(!(inode->i_state & I_FREEING));
      BUG_ON(inode->i_state & I_CLEAR);
      inode_sync_wait(inode);
      DQUOT_DROP(inode);
      if (inode->i_sb->s_op->clear_inode)
            inode->i_sb->s_op->clear_inode(inode);
      if (S_ISBLK(inode->i_mode) && inode->i_bdev)
            bd_forget(inode);
      if (S_ISCHR(inode->i_mode) && 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_first_entry(head, struct inode, i_list);
            list_del(&inode->i_list);

            if (inode->i_data.nrpages)
                  truncate_inode_pages(&inode->i_data, 0);
            clear_inode(inode);

            spin_lock(&inode_lock);
            hlist_del_init(&inode->i_hash);
            list_del_init(&inode->i_sb_list);
            spin_unlock(&inode_lock);

            wake_up_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_mutex 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)) {
                  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;
}

/**
 *    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);

      mutex_lock(&iprune_mutex);
      spin_lock(&inode_lock);
      inotify_unmount_inodes(&sb->s_inodes);
      busy = invalidate_list(&sb->s_inodes, &throw_away);
      spin_unlock(&inode_lock);

      dispose_list(&throw_away);
      mutex_unlock(&iprune_mutex);

      return busy;
}

EXPORT_SYMBOL(invalidate_inodes);

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;

      mutex_lock(&iprune_mutex);
      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_mapping_pages(&inode->i_data,
                                                0, -1);
                  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;
            }
            list_move(&inode->i_list, &freeable);
            inode->i_state |= I_FREEING;
            nr_pruned++;
      }
      inodes_stat.nr_unused -= nr_pruned;
      if (current_is_kswapd())
            __count_vm_events(KSWAPD_INODESTEAL, reap);
      else
            __count_vm_events(PGINODESTEAL, reap);
      spin_unlock(&inode_lock);

      dispose_list(&freeable);
      mutex_unlock(&iprune_mutex);
}

/*
 * 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, gfp_t 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 struct shrinker icache_shrinker = {
      .shrink = shrink_icache_memory,
      .seeks = DEFAULT_SEEKS,
};

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|I_WILL_FREE)) {
                  __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|I_WILL_FREE)) {
                  __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. The default gfp_mask
 *    for allocations related to inode->i_mapping is GFP_HIGHUSER_PAGECACHE.
 *    If HIGHMEM pages are unsuitable or it is known that pages allocated
 *    for the page cache are not reclaimable or migratable,
 *    mapping_set_gfp_mask() must be called with suitable flags on the
 *    newly created inode's mapping
 *
 */
struct inode *new_inode(struct super_block *sb)
{
      /*
       * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
       * error if st_ino won't fit in target struct field. Use 32bit counter
       * here to attempt to avoid that.
       */
      static unsigned int 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)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
      if (inode->i_mode & S_IFDIR) {
            struct file_system_type *type = inode->i_sb->s_type;

            /*
             * ensure nobody is actually holding i_mutex
             */
            mutex_destroy(&inode->i_mutex);
            mutex_init(&inode->i_mutex);
            lockdep_set_class(&inode->i_mutex, &type->i_mutex_dir_key);
      }
#endif
      /*
       * 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 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)
{
      /*
       * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
       * error if st_ino won't fit in target struct field. Use 32bit counter
       * here to attempt to avoid that.
       */
      static unsigned int counter;
      struct inode *inode;
      struct hlist_head *head;
      ino_t res;

      spin_lock(&inode_lock);
      do {
            if (counter <= max_reserved)
                  counter = max_reserved + 1;
            res = counter++;
            head = inode_hashtable + hash(sb, res);
            inode = find_inode_fast(sb, head, res);
      } while (inode != NULL);
      spin_unlock(&inode_lock);

      return res;
}
EXPORT_SYMBOL(iunique);

struct inode *igrab(struct inode *inode)
{
      spin_lock(&inode_lock);
      if (!(inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE)))
            __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
 * @wait:   if true wait for the inode to be unlocked, if false do not
 *
 * 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 struct inode *ifind(struct super_block *sb,
            struct hlist_head *head, int (*test)(struct inode *, void *),
            void *data, const int wait)
{
      struct inode *inode;

      spin_lock(&inode_lock);
      inode = find_inode(sb, head, test, data);
      if (inode) {
            __iget(inode);
            spin_unlock(&inode_lock);
            if (likely(wait))
                  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 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_nowait - 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.  Note, the inode lock is not waited upon so you have to be
 * very careful what you do with the returned inode.  You probably should be
 * using ilookup5() instead.
 *
 * Otherwise NULL is returned.
 *
 * Note, @test is called with the inode_lock held, so can't sleep.
 */
struct inode *ilookup5_nowait(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, 0);
}

EXPORT_SYMBOL(ilookup5_nowait);

/**
 * 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 lock is waited upon and 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, 1);
}

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, 1);
      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)
{
      const 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);

      security_inode_delete(inode);

      if (op->delete_inode) {
            void (*delete)(struct inode *) = op->delete_inode;
            if (!is_bad_inode(inode))
                  DQUOT_INIT(inode);
            /* Filesystems implementing their own
             * s_op->delete_inode are required to call
             * truncate_inode_pages and clear_inode()
             * internally */
            delete(inode);
      } else {
            truncate_inode_pages(&inode->i_data, 0);
            clear_inode(inode);
      }
      spin_lock(&inode_lock);
      hlist_del_init(&inode->i_hash);
      spin_unlock(&inode_lock);
      wake_up_inode(inode);
      BUG_ON(inode->i_state != I_CLEAR);
      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_SYNC)))
                  list_move(&inode->i_list, &inode_unused);
            inodes_stat.nr_unused++;
            if (sb->s_flags & MS_ACTIVE) {
                  spin_unlock(&inode_lock);
                  return;
            }
            inode->i_state |= I_WILL_FREE;
            spin_unlock(&inode_lock);
            write_inode_now(inode, 1);
            spin_lock(&inode_lock);
            inode->i_state &= ~I_WILL_FREE;
            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);
      wake_up_inode(inode);
      destroy_inode(inode);
}

/*
 * Normal UNIX filesystem behaviour: delete the
 * inode when the usage count drops to zero, and
 * i_nlink is zero.
 */
void generic_drop_inode(struct inode *inode)
{
      if (!inode->i_nlink)
            generic_delete_inode(inode);
      else
            generic_forget_inode(inode);
}

EXPORT_SYMBOL_GPL(generic_drop_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)
{
      const 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) {
            const 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);

/**
 *    touch_atime -     update the access time
 *    @mnt: mount the inode is accessed on
 *    @dentry: dentry 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 touch_atime(struct vfsmount *mnt, struct dentry *dentry)
{
      struct inode *inode = dentry->d_inode;
      struct timespec now;

      if (inode->i_flags & S_NOATIME)
            return;
      if (IS_NOATIME(inode))
            return;
      if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode))
            return;

      /*
       * We may have a NULL vfsmount when coming from NFSD
       */
      if (mnt) {
            if (mnt->mnt_flags & MNT_NOATIME)
                  return;
            if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
                  return;

            if (mnt->mnt_flags & MNT_RELATIME) {
                  /*
                   * With relative atime, only update atime if the
                   * previous atime is earlier than either the ctime or
                   * mtime.
                   */
                  if (timespec_compare(&inode->i_mtime,
                                    &inode->i_atime) < 0 &&
                      timespec_compare(&inode->i_ctime,
                                    &inode->i_atime) < 0)
                        return;
            }
      }

      now = current_fs_time(inode->i_sb);
      if (timespec_equal(&inode->i_atime, &now))
            return;

      inode->i_atime = now;
      mark_inode_dirty_sync(inode);
}
EXPORT_SYMBOL(touch_atime);

/**
 *    file_update_time  -     update mtime and ctime time
 *    @file: file accessed
 *
 *    Update the mtime and ctime members of an inode and mark the inode
 *    for writeback.  Note that this function is meant exclusively for
 *    usage in the file write path of filesystems, and filesystems may
 *    choose to explicitly ignore update via this function with the
 *    S_NOCTIME inode flag, e.g. for network filesystem where these
 *    timestamps are handled by the server.
 */

void file_update_time(struct file *file)
{
      struct inode *inode = file->f_path.dentry->d_inode;
      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)) {
            inode->i_mtime = now;
            sync_it = 1;
      }

      if (!timespec_equal(&inode->i_ctime, &now)) {
            inode->i_ctime = now;
            sync_it = 1;
      }

      if (sync_it)
            mark_inode_dirty_sync(inode);
}

EXPORT_SYMBOL(file_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);

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 function waits
 * until the deletion _might_ have completed.  Callers are responsible
 * to recheck inode state.
 *
 * It doesn't matter if I_LOCK is not set initially, a call to
 * wake_up_inode() after removing from the hash list will DTRT.
 *
 * 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);
      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);
}

/*
 * We rarely want to lock two inodes that do not have a parent/child
 * relationship (such as directory, child inode) simultaneously. The
 * vast majority of file systems should be able to get along fine
 * without this. Do not use these functions except as a last resort.
 */
void inode_double_lock(struct inode *inode1, struct inode *inode2)
{
      if (inode1 == NULL || inode2 == NULL || inode1 == inode2) {
            if (inode1)
                  mutex_lock(&inode1->i_mutex);
            else if (inode2)
                  mutex_lock(&inode2->i_mutex);
            return;
      }

      if (inode1 < inode2) {
            mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
            mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
      } else {
            mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
            mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
      }
}
EXPORT_SYMBOL(inode_double_lock);

void inode_double_unlock(struct inode *inode1, struct inode *inode2)
{
      if (inode1)
            mutex_unlock(&inode1->i_mutex);

      if (inode2 && inode2 != inode1)
            mutex_unlock(&inode2->i_mutex);
}
EXPORT_SYMBOL(inode_double_unlock);

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(void)
{
      int loop;

      /* inode slab cache */
      inode_cachep = kmem_cache_create("inode_cache",
                               sizeof(struct inode),
                               0,
                               (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
                               SLAB_MEM_SPREAD),
                               init_once);
      register_shrinker(&icache_shrinker);

      /* 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);

Generated by  Doxygen 1.6.0   Back to index