inode.c

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/*
 * (C) 1997 Linus Torvalds
 * (C) 1999 Andrea Arcangeli <[email protected]> (dynamic inode allocation)
 */
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/backing-dev.h>
#include <linux/hash.h>
#include <linux/swap.h>
#include <linux/security.h>
#include <linux/cdev.h>
#include <linux/bootmem.h>
#include <linux/fsnotify.h>
#include <linux/mount.h>
#include <linux/posix_acl.h>
#include <linux/prefetch.h>
#include <linux/buffer_head.h> /* for inode_has_buffers */
#include <linux/ratelimit.h>
#include "internal.h"

/*
 * Inode locking rules:
 *
 * inode->i_lock protects:
 *   inode->i_state, inode->i_hash, __iget()
 * inode->i_sb->s_inode_lru_lock protects:
 *   inode->i_sb->s_inode_lru, inode->i_lru
 * inode_sb_list_lock protects:
 *   sb->s_inodes, inode->i_sb_list
 * bdi->wb.list_lock protects:
 *   bdi->wb.b_{dirty,io,more_io}, inode->i_wb_list
 * inode_hash_lock protects:
 *   inode_hashtable, inode->i_hash
 *
 * Lock ordering:
 *
 * inode_sb_list_lock
 *   inode->i_lock
 *     inode->i_sb->s_inode_lru_lock
 *
 * bdi->wb.list_lock
 *   inode->i_lock
 *
 * inode_hash_lock
 *   inode_sb_list_lock
 *   inode->i_lock
 *
 * iunique_lock
 *   inode_hash_lock
 */

static unsigned int i_hash_mask __read_mostly;
static unsigned int i_hash_shift __read_mostly;
static struct hlist_head *inode_hashtable __read_mostly;
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);

__cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);

/*
 * Empty aops. Can be used for the cases where the user does not
 * define any of the address_space operations.
 */
const struct address_space_operations empty_aops = {
};
EXPORT_SYMBOL(empty_aops);

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

static DEFINE_PER_CPU(unsigned int, nr_inodes);
static DEFINE_PER_CPU(unsigned int, nr_unused);

static struct kmem_cache *inode_cachep __read_mostly;

static int get_nr_inodes(void)
{
    int i;
    int sum = 0;
    for_each_possible_cpu(i)
        sum += per_cpu(nr_inodes, i);
    return sum < 0 ? 0 : sum;
}

static inline int get_nr_inodes_unused(void)
{
    int i;
    int sum = 0;
    for_each_possible_cpu(i)
        sum += per_cpu(nr_unused, i);
    return sum < 0 ? 0 : sum;
}

int get_nr_dirty_inodes(void)
{
    /* not actually dirty inodes, but a wild approximation */
    int nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
    return nr_dirty > 0 ? nr_dirty : 0;
}

/*
 * Handle nr_inode sysctl
 */
#ifdef CONFIG_SYSCTL
int proc_nr_inodes(ctl_table *table, int write,
           void __user *buffer, size_t *lenp, loff_t *ppos)
{
    inodes_stat.nr_inodes = get_nr_inodes();
    inodes_stat.nr_unused = get_nr_inodes_unused();
    return proc_dointvec(table, write, buffer, lenp, ppos);
}
#endif

int inode_init_always(struct super_block *sb, struct inode *inode)
{
    static const struct inode_operations empty_iops;
    static const struct file_operations empty_fops;
    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;
    inode->i_opflags = 0;
    i_uid_write(inode, 0);
    i_gid_write(inode, 0);
    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))
        goto out;
    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);

    atomic_set(&inode->i_dio_count, 0);

    mapping->a_ops = &empty_aops;
    mapping->host = inode;
    mapping->flags = 0;
    mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
    mapping->assoc_mapping = NULL;
    mapping->backing_dev_info = &default_backing_dev_info;
    mapping->writeback_index = 0;

    /*
     * 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->i_mapping->backing_dev_info;
        mapping->backing_dev_info = bdi;
    }
    inode->i_private = NULL;
    inode->i_mapping = mapping;
    INIT_HLIST_HEAD(&inode->i_dentry);  /* buggered by rcu freeing */
#ifdef CONFIG_FS_POSIX_ACL
    inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
#endif

#ifdef CONFIG_FSNOTIFY
    inode->i_fsnotify_mask = 0;
#endif

    this_cpu_inc(nr_inodes);

    return 0;
out:
    return -ENOMEM;
}
EXPORT_SYMBOL(inode_init_always);

static struct inode *alloc_inode(struct super_block *sb)
{
    struct inode *inode;

    if (sb->s_op->alloc_inode)
        inode = sb->s_op->alloc_inode(sb);
    else
        inode = kmem_cache_alloc(inode_cachep, GFP_KERNEL);

    if (!inode)
        return NULL;

    if (unlikely(inode_init_always(sb, 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;
    }

    return inode;
}

void free_inode_nonrcu(struct inode *inode)
{
    kmem_cache_free(inode_cachep, inode);
}
EXPORT_SYMBOL(free_inode_nonrcu);

void __destroy_inode(struct inode *inode)
{
    BUG_ON(inode_has_buffers(inode));
    security_inode_free(inode);
    fsnotify_inode_delete(inode);
    if (!inode->i_nlink) {
        WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
        atomic_long_dec(&inode->i_sb->s_remove_count);
    }

#ifdef CONFIG_FS_POSIX_ACL
    if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
        posix_acl_release(inode->i_acl);
    if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
        posix_acl_release(inode->i_default_acl);
#endif
    this_cpu_dec(nr_inodes);
}
EXPORT_SYMBOL(__destroy_inode);

static void i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(inode_cachep, inode);
}

static void destroy_inode(struct inode *inode)
{
    BUG_ON(!list_empty(&inode->i_lru));
    __destroy_inode(inode);
    if (inode->i_sb->s_op->destroy_inode)
        inode->i_sb->s_op->destroy_inode(inode);
    else
        call_rcu(&inode->i_rcu, i_callback);
}

void drop_nlink(struct inode *inode)
{
    WARN_ON(inode->i_nlink == 0);
    inode->__i_nlink--;
    if (!inode->i_nlink)
        atomic_long_inc(&inode->i_sb->s_remove_count);
}
EXPORT_SYMBOL(drop_nlink);

void clear_nlink(struct inode *inode)
{
    if (inode->i_nlink) {
        inode->__i_nlink = 0;
        atomic_long_inc(&inode->i_sb->s_remove_count);
    }
}
EXPORT_SYMBOL(clear_nlink);

void set_nlink(struct inode *inode, unsigned int nlink)
{
    if (!nlink) {
        clear_nlink(inode);
    } else {
        /* Yes, some filesystems do change nlink from zero to one */
        if (inode->i_nlink == 0)
            atomic_long_dec(&inode->i_sb->s_remove_count);

        inode->__i_nlink = nlink;
    }
}
EXPORT_SYMBOL(set_nlink);

void inc_nlink(struct inode *inode)
{
    if (WARN_ON(inode->i_nlink == 0))
        atomic_long_dec(&inode->i_sb->s_remove_count);

    inode->__i_nlink++;
}
EXPORT_SYMBOL(inc_nlink);

void address_space_init_once(struct address_space *mapping)
{
    memset(mapping, 0, sizeof(*mapping));
    INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
    spin_lock_init(&mapping->tree_lock);
    mutex_init(&mapping->i_mmap_mutex);
    INIT_LIST_HEAD(&mapping->private_list);
    spin_lock_init(&mapping->private_lock);
    mapping->i_mmap = RB_ROOT;
    INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);
}
EXPORT_SYMBOL(address_space_init_once);

/*
 * 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_devices);
    INIT_LIST_HEAD(&inode->i_wb_list);
    INIT_LIST_HEAD(&inode->i_lru);
    address_space_init_once(&inode->i_data);
    i_size_ordered_init(inode);
#ifdef CONFIG_FSNOTIFY
    INIT_HLIST_HEAD(&inode->i_fsnotify_marks);
#endif
}
EXPORT_SYMBOL(inode_init_once);

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

    inode_init_once(inode);
}

/*
 * inode->i_lock must be held
 */
void __iget(struct inode *inode)
{
    atomic_inc(&inode->i_count);
}

/*
 * get additional reference to inode; caller must already hold one.
 */
void ihold(struct inode *inode)
{
    WARN_ON(atomic_inc_return(&inode->i_count) < 2);
}
EXPORT_SYMBOL(ihold);

static void inode_lru_list_add(struct inode *inode)
{
    spin_lock(&inode->i_sb->s_inode_lru_lock);
    if (list_empty(&inode->i_lru)) {
        list_add(&inode->i_lru, &inode->i_sb->s_inode_lru);
        inode->i_sb->s_nr_inodes_unused++;
        this_cpu_inc(nr_unused);
    }
    spin_unlock(&inode->i_sb->s_inode_lru_lock);
}

/*
 * Add inode to LRU if needed (inode is unused and clean).
 *
 * Needs inode->i_lock held.
 */
void inode_add_lru(struct inode *inode)
{
    if (!(inode->i_state & (I_DIRTY | I_SYNC | I_FREEING | I_WILL_FREE)) &&
        !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
        inode_lru_list_add(inode);
}


static void inode_lru_list_del(struct inode *inode)
{
    spin_lock(&inode->i_sb->s_inode_lru_lock);
    if (!list_empty(&inode->i_lru)) {
        list_del_init(&inode->i_lru);
        inode->i_sb->s_nr_inodes_unused--;
        this_cpu_dec(nr_unused);
    }
    spin_unlock(&inode->i_sb->s_inode_lru_lock);
}

void inode_sb_list_add(struct inode *inode)
{
    spin_lock(&inode_sb_list_lock);
    list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
    spin_unlock(&inode_sb_list_lock);
}
EXPORT_SYMBOL_GPL(inode_sb_list_add);

static inline void inode_sb_list_del(struct inode *inode)
{
    if (!list_empty(&inode->i_sb_list)) {
        spin_lock(&inode_sb_list_lock);
        list_del_init(&inode->i_sb_list);
        spin_unlock(&inode_sb_list_lock);
    }
}

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_hash_shift);
    return tmp & i_hash_mask;
}

void __insert_inode_hash(struct inode *inode, unsigned long hashval)
{
    struct hlist_head *b = inode_hashtable + hash(inode->i_sb, hashval);

    spin_lock(&inode_hash_lock);
    spin_lock(&inode->i_lock);
    hlist_add_head(&inode->i_hash, b);
    spin_unlock(&inode->i_lock);
    spin_unlock(&inode_hash_lock);
}
EXPORT_SYMBOL(__insert_inode_hash);

void __remove_inode_hash(struct inode *inode)
{
    spin_lock(&inode_hash_lock);
    spin_lock(&inode->i_lock);
    hlist_del_init(&inode->i_hash);
    spin_unlock(&inode->i_lock);
    spin_unlock(&inode_hash_lock);
}
EXPORT_SYMBOL(__remove_inode_hash);

void clear_inode(struct inode *inode)
{
    might_sleep();
    /*
     * We have to cycle tree_lock here because reclaim can be still in the
     * process of removing the last page (in __delete_from_page_cache())
     * and we must not free mapping under it.
     */
    spin_lock_irq(&inode->i_data.tree_lock);
    BUG_ON(inode->i_data.nrpages);
    spin_unlock_irq(&inode->i_data.tree_lock);
    BUG_ON(!list_empty(&inode->i_data.private_list));
    BUG_ON(!(inode->i_state & I_FREEING));
    BUG_ON(inode->i_state & I_CLEAR);
    /* don't need i_lock here, no concurrent mods to i_state */
    inode->i_state = I_FREEING | I_CLEAR;
}
EXPORT_SYMBOL(clear_inode);

/*
 * Free the inode passed in, removing it from the lists it is still connected
 * to. We remove any pages still attached to the inode and wait for any IO that
 * is still in progress before finally destroying the inode.
 *
 * An inode must already be marked I_FREEING so that we avoid the inode being
 * moved back onto lists if we race with other code that manipulates the lists
 * (e.g. writeback_single_inode). The caller is responsible for setting this.
 *
 * An inode must already be removed from the LRU list before being evicted from
 * the cache. This should occur atomically with setting the I_FREEING state
 * flag, so no inodes here should ever be on the LRU when being evicted.
 */
static void evict(struct inode *inode)
{
    const struct super_operations *op = inode->i_sb->s_op;

    BUG_ON(!(inode->i_state & I_FREEING));
    BUG_ON(!list_empty(&inode->i_lru));

    if (!list_empty(&inode->i_wb_list))
        inode_wb_list_del(inode);

    inode_sb_list_del(inode);

    /*
     * Wait for flusher thread to be done with the inode so that filesystem
     * does not start destroying it while writeback is still running. Since
     * the inode has I_FREEING set, flusher thread won't start new work on
     * the inode.  We just have to wait for running writeback to finish.
     */
    inode_wait_for_writeback(inode);

    if (op->evict_inode) {
        op->evict_inode(inode);
    } else {
        if (inode->i_data.nrpages)
            truncate_inode_pages(&inode->i_data, 0);
        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);

    remove_inode_hash(inode);

    spin_lock(&inode->i_lock);
    wake_up_bit(&inode->i_state, __I_NEW);
    BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
    spin_unlock(&inode->i_lock);

    destroy_inode(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)
{
    while (!list_empty(head)) {
        struct inode *inode;

        inode = list_first_entry(head, struct inode, i_lru);
        list_del_init(&inode->i_lru);

        evict(inode);
    }
}

void evict_inodes(struct super_block *sb)
{
    struct inode *inode, *next;
    LIST_HEAD(dispose);

    spin_lock(&inode_sb_list_lock);
    list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
        if (atomic_read(&inode->i_count))
            continue;

        spin_lock(&inode->i_lock);
        if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
            spin_unlock(&inode->i_lock);
            continue;
        }

        inode->i_state |= I_FREEING;
        inode_lru_list_del(inode);
        spin_unlock(&inode->i_lock);
        list_add(&inode->i_lru, &dispose);
    }
    spin_unlock(&inode_sb_list_lock);

    dispose_list(&dispose);
}

int invalidate_inodes(struct super_block *sb, bool kill_dirty)
{
    int busy = 0;
    struct inode *inode, *next;
    LIST_HEAD(dispose);

    spin_lock(&inode_sb_list_lock);
    list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
        spin_lock(&inode->i_lock);
        if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
            spin_unlock(&inode->i_lock);
            continue;
        }
        if (inode->i_state & I_DIRTY && !kill_dirty) {
            spin_unlock(&inode->i_lock);
            busy = 1;
            continue;
        }
        if (atomic_read(&inode->i_count)) {
            spin_unlock(&inode->i_lock);
            busy = 1;
            continue;
        }

        inode->i_state |= I_FREEING;
        inode_lru_list_del(inode);
        spin_unlock(&inode->i_lock);
        list_add(&inode->i_lru, &dispose);
    }
    spin_unlock(&inode_sb_list_lock);

    dispose_list(&dispose);

    return busy;
}

static int can_unuse(struct inode *inode)
{
    if (inode->i_state & ~I_REFERENCED)
        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;
}

/*
 * Walk the superblock inode LRU for freeable inodes and attempt to free them.
 * This is called from the superblock shrinker function with a number of inodes
 * to trim from the LRU. Inodes to be freed 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.  If the inode has metadata buffers attached to
 * mapping->private_list then try to remove them.
 *
 * If the inode has the I_REFERENCED flag set, then it means that it has been
 * used recently - the flag is set in iput_final(). When we encounter such an
 * inode, clear the flag and move it to the back of the LRU so it gets another
 * pass through the LRU before it gets reclaimed. This is necessary because of
 * the fact we are doing lazy LRU updates to minimise lock contention so the
 * LRU does not have strict ordering. Hence we don't want to reclaim inodes
 * with this flag set because they are the inodes that are out of order.
 */
void prune_icache_sb(struct super_block *sb, int nr_to_scan)
{
    LIST_HEAD(freeable);
    int nr_scanned;
    unsigned long reap = 0;

    spin_lock(&sb->s_inode_lru_lock);
    for (nr_scanned = nr_to_scan; nr_scanned >= 0; nr_scanned--) {
        struct inode *inode;

        if (list_empty(&sb->s_inode_lru))
            break;

        inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);

        /*
         * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
         * so use a trylock. If we fail to get the lock, just move the
         * inode to the back of the list so we don't spin on it.
         */
        if (!spin_trylock(&inode->i_lock)) {
            list_move_tail(&inode->i_lru, &sb->s_inode_lru);
            continue;
        }

        /*
         * Referenced or dirty inodes are still in use. Give them
         * another pass through the LRU as we canot reclaim them now.
         */
        if (atomic_read(&inode->i_count) ||
            (inode->i_state & ~I_REFERENCED)) {
            list_del_init(&inode->i_lru);
            spin_unlock(&inode->i_lock);
            sb->s_nr_inodes_unused--;
            this_cpu_dec(nr_unused);
            continue;
        }

        /* recently referenced inodes get one more pass */
        if (inode->i_state & I_REFERENCED) {
            inode->i_state &= ~I_REFERENCED;
            list_move(&inode->i_lru, &sb->s_inode_lru);
            spin_unlock(&inode->i_lock);
            continue;
        }
        if (inode_has_buffers(inode) || inode->i_data.nrpages) {
            __iget(inode);
            spin_unlock(&inode->i_lock);
            spin_unlock(&sb->s_inode_lru_lock);
            if (remove_inode_buffers(inode))
                reap += invalidate_mapping_pages(&inode->i_data,
                                0, -1);
            iput(inode);
            spin_lock(&sb->s_inode_lru_lock);

            if (inode != list_entry(sb->s_inode_lru.next,
                        struct inode, i_lru))
                continue;   /* wrong inode or list_empty */
            /* avoid lock inversions with trylock */
            if (!spin_trylock(&inode->i_lock))
                continue;
            if (!can_unuse(inode)) {
                spin_unlock(&inode->i_lock);
                continue;
            }
        }
        WARN_ON(inode->i_state & I_NEW);
        inode->i_state |= I_FREEING;
        spin_unlock(&inode->i_lock);

        list_move(&inode->i_lru, &freeable);
        sb->s_nr_inodes_unused--;
        this_cpu_dec(nr_unused);
    }
    if (current_is_kswapd())
        __count_vm_events(KSWAPD_INODESTEAL, reap);
    else
        __count_vm_events(PGINODESTEAL, reap);
    spin_unlock(&sb->s_inode_lru_lock);
    if (current->reclaim_state)
        current->reclaim_state->reclaimed_slab += reap;

    dispose_list(&freeable);
}

static void __wait_on_freeing_inode(struct inode *inode);
/*
 * Called with the inode lock held.
 */
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_entry(inode, node, head, i_hash) {
        spin_lock(&inode->i_lock);
        if (inode->i_sb != sb) {
            spin_unlock(&inode->i_lock);
            continue;
        }
        if (!test(inode, data)) {
            spin_unlock(&inode->i_lock);
            continue;
        }
        if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
            __wait_on_freeing_inode(inode);
            goto repeat;
        }
        __iget(inode);
        spin_unlock(&inode->i_lock);
        return inode;
    }
    return 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_entry(inode, node, head, i_hash) {
        spin_lock(&inode->i_lock);
        if (inode->i_ino != ino) {
            spin_unlock(&inode->i_lock);
            continue;
        }
        if (inode->i_sb != sb) {
            spin_unlock(&inode->i_lock);
            continue;
        }
        if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
            __wait_on_freeing_inode(inode);
            goto repeat;
        }
        __iget(inode);
        spin_unlock(&inode->i_lock);
        return inode;
    }
    return NULL;
}

/*
 * Each cpu owns a range of LAST_INO_BATCH numbers.
 * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations,
 * to renew the exhausted range.
 *
 * This does not significantly increase overflow rate because every CPU can
 * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is
 * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the
 * 2^32 range, and is a worst-case. Even a 50% wastage would only increase
 * overflow rate by 2x, which does not seem too significant.
 *
 * 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.
 */
#define LAST_INO_BATCH 1024
static DEFINE_PER_CPU(unsigned int, last_ino);

unsigned int get_next_ino(void)
{
    unsigned int *p = &get_cpu_var(last_ino);
    unsigned int res = *p;

#ifdef CONFIG_SMP
    if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
        static atomic_t shared_last_ino;
        int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);

        res = next - LAST_INO_BATCH;
    }
#endif

    *p = ++res;
    put_cpu_var(last_ino);
    return res;
}
EXPORT_SYMBOL(get_next_ino);

struct inode *new_inode_pseudo(struct super_block *sb)
{
    struct inode *inode = alloc_inode(sb);

    if (inode) {
        spin_lock(&inode->i_lock);
        inode->i_state = 0;
        spin_unlock(&inode->i_lock);
        INIT_LIST_HEAD(&inode->i_sb_list);
    }
    return inode;
}

struct inode *new_inode(struct super_block *sb)
{
    struct inode *inode;

    spin_lock_prefetch(&inode_sb_list_lock);

    inode = new_inode_pseudo(sb);
    if (inode)
        inode_sb_list_add(inode);
    return inode;
}
EXPORT_SYMBOL(new_inode);

#ifdef CONFIG_DEBUG_LOCK_ALLOC
void lockdep_annotate_inode_mutex_key(struct inode *inode)
{
    if (S_ISDIR(inode->i_mode)) {
        struct file_system_type *type = inode->i_sb->s_type;

        /* Set new key only if filesystem hasn't already changed it */
        if (lockdep_match_class(&inode->i_mutex, &type->i_mutex_key)) {
            /*
             * 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);
        }
    }
}
EXPORT_SYMBOL(lockdep_annotate_inode_mutex_key);
#endif

void unlock_new_inode(struct inode *inode)
{
    lockdep_annotate_inode_mutex_key(inode);
    spin_lock(&inode->i_lock);
    WARN_ON(!(inode->i_state & I_NEW));
    inode->i_state &= ~I_NEW;
    smp_mb();
    wake_up_bit(&inode->i_state, __I_NEW);
    spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL(unlock_new_inode);

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;

    spin_lock(&inode_hash_lock);
    inode = find_inode(sb, head, test, data);
    spin_unlock(&inode_hash_lock);

    if (inode) {
        wait_on_inode(inode);
        return inode;
    }

    inode = alloc_inode(sb);
    if (inode) {
        struct inode *old;

        spin_lock(&inode_hash_lock);
        /* We released the lock, so.. */
        old = find_inode(sb, head, test, data);
        if (!old) {
            if (set(inode, data))
                goto set_failed;

            spin_lock(&inode->i_lock);
            inode->i_state = I_NEW;
            hlist_add_head(&inode->i_hash, head);
            spin_unlock(&inode->i_lock);
            inode_sb_list_add(inode);
            spin_unlock(&inode_hash_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.
         */
        spin_unlock(&inode_hash_lock);
        destroy_inode(inode);
        inode = old;
        wait_on_inode(inode);
    }
    return inode;

set_failed:
    spin_unlock(&inode_hash_lock);
    destroy_inode(inode);
    return NULL;
}
EXPORT_SYMBOL(iget5_locked);

struct inode *iget_locked(struct super_block *sb, unsigned long ino)
{
    struct hlist_head *head = inode_hashtable + hash(sb, ino);
    struct inode *inode;

    spin_lock(&inode_hash_lock);
    inode = find_inode_fast(sb, head, ino);
    spin_unlock(&inode_hash_lock);
    if (inode) {
        wait_on_inode(inode);
        return inode;
    }

    inode = alloc_inode(sb);
    if (inode) {
        struct inode *old;

        spin_lock(&inode_hash_lock);
        /* We released the lock, so.. */
        old = find_inode_fast(sb, head, ino);
        if (!old) {
            inode->i_ino = ino;
            spin_lock(&inode->i_lock);
            inode->i_state = I_NEW;
            hlist_add_head(&inode->i_hash, head);
            spin_unlock(&inode->i_lock);
            inode_sb_list_add(inode);
            spin_unlock(&inode_hash_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.
         */
        spin_unlock(&inode_hash_lock);
        destroy_inode(inode);
        inode = old;
        wait_on_inode(inode);
    }
    return inode;
}
EXPORT_SYMBOL(iget_locked);

/*
 * search the inode cache for a matching inode number.
 * If we find one, then the inode number we are trying to
 * allocate is not unique and so we should not use it.
 *
 * Returns 1 if the inode number is unique, 0 if it is not.
 */
static int test_inode_iunique(struct super_block *sb, unsigned long ino)
{
    struct hlist_head *b = inode_hashtable + hash(sb, ino);
    struct hlist_node *node;
    struct inode *inode;

    spin_lock(&inode_hash_lock);
    hlist_for_each_entry(inode, node, b, i_hash) {
        if (inode->i_ino == ino && inode->i_sb == sb) {
            spin_unlock(&inode_hash_lock);
            return 0;
        }
    }
    spin_unlock(&inode_hash_lock);

    return 1;
}

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 DEFINE_SPINLOCK(iunique_lock);
    static unsigned int counter;
    ino_t res;

    spin_lock(&iunique_lock);
    do {
        if (counter <= max_reserved)
            counter = max_reserved + 1;
        res = counter++;
    } while (!test_inode_iunique(sb, res));
    spin_unlock(&iunique_lock);

    return res;
}
EXPORT_SYMBOL(iunique);

struct inode *igrab(struct inode *inode)
{
    spin_lock(&inode->i_lock);
    if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) {
        __iget(inode);
        spin_unlock(&inode->i_lock);
    } else {
        spin_unlock(&inode->i_lock);
        /*
         * 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;
    }
    return inode;
}
EXPORT_SYMBOL(igrab);

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);
    struct inode *inode;

    spin_lock(&inode_hash_lock);
    inode = find_inode(sb, head, test, data);
    spin_unlock(&inode_hash_lock);

    return inode;
}
EXPORT_SYMBOL(ilookup5_nowait);

struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
        int (*test)(struct inode *, void *), void *data)
{
    struct inode *inode = ilookup5_nowait(sb, hashval, test, data);

    if (inode)
        wait_on_inode(inode);
    return inode;
}
EXPORT_SYMBOL(ilookup5);

struct inode *ilookup(struct super_block *sb, unsigned long ino)
{
    struct hlist_head *head = inode_hashtable + hash(sb, ino);
    struct inode *inode;

    spin_lock(&inode_hash_lock);
    inode = find_inode_fast(sb, head, ino);
    spin_unlock(&inode_hash_lock);

    if (inode)
        wait_on_inode(inode);
    return inode;
}
EXPORT_SYMBOL(ilookup);

int insert_inode_locked(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    ino_t ino = inode->i_ino;
    struct hlist_head *head = inode_hashtable + hash(sb, ino);

    while (1) {
        struct hlist_node *node;
        struct inode *old = NULL;
        spin_lock(&inode_hash_lock);
        hlist_for_each_entry(old, node, head, i_hash) {
            if (old->i_ino != ino)
                continue;
            if (old->i_sb != sb)
                continue;
            spin_lock(&old->i_lock);
            if (old->i_state & (I_FREEING|I_WILL_FREE)) {
                spin_unlock(&old->i_lock);
                continue;
            }
            break;
        }
        if (likely(!node)) {
            spin_lock(&inode->i_lock);
            inode->i_state |= I_NEW;
            hlist_add_head(&inode->i_hash, head);
            spin_unlock(&inode->i_lock);
            spin_unlock(&inode_hash_lock);
            return 0;
        }
        __iget(old);
        spin_unlock(&old->i_lock);
        spin_unlock(&inode_hash_lock);
        wait_on_inode(old);
        if (unlikely(!inode_unhashed(old))) {
            iput(old);
            return -EBUSY;
        }
        iput(old);
    }
}
EXPORT_SYMBOL(insert_inode_locked);

int insert_inode_locked4(struct inode *inode, unsigned long hashval,
        int (*test)(struct inode *, void *), void *data)
{
    struct super_block *sb = inode->i_sb;
    struct hlist_head *head = inode_hashtable + hash(sb, hashval);

    while (1) {
        struct hlist_node *node;
        struct inode *old = NULL;

        spin_lock(&inode_hash_lock);
        hlist_for_each_entry(old, node, head, i_hash) {
            if (old->i_sb != sb)
                continue;
            if (!test(old, data))
                continue;
            spin_lock(&old->i_lock);
            if (old->i_state & (I_FREEING|I_WILL_FREE)) {
                spin_unlock(&old->i_lock);
                continue;
            }
            break;
        }
        if (likely(!node)) {
            spin_lock(&inode->i_lock);
            inode->i_state |= I_NEW;
            hlist_add_head(&inode->i_hash, head);
            spin_unlock(&inode->i_lock);
            spin_unlock(&inode_hash_lock);
            return 0;
        }
        __iget(old);
        spin_unlock(&old->i_lock);
        spin_unlock(&inode_hash_lock);
        wait_on_inode(old);
        if (unlikely(!inode_unhashed(old))) {
            iput(old);
            return -EBUSY;
        }
        iput(old);
    }
}
EXPORT_SYMBOL(insert_inode_locked4);


int generic_delete_inode(struct inode *inode)
{
    return 1;
}
EXPORT_SYMBOL(generic_delete_inode);

/*
 * Called when we're dropping the last reference
 * to an inode.
 *
 * Call the FS "drop_inode()" function, defaulting to
 * the legacy UNIX filesystem behaviour.  If it tells
 * us to evict inode, do so.  Otherwise, retain inode
 * in cache if fs is alive, sync and evict if fs is
 * shutting down.
 */
static void iput_final(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    const struct super_operations *op = inode->i_sb->s_op;
    int drop;

    WARN_ON(inode->i_state & I_NEW);

    if (op->drop_inode)
        drop = op->drop_inode(inode);
    else
        drop = generic_drop_inode(inode);

    if (!drop && (sb->s_flags & MS_ACTIVE)) {
        inode->i_state |= I_REFERENCED;
        inode_add_lru(inode);
        spin_unlock(&inode->i_lock);
        return;
    }

    if (!drop) {
        inode->i_state |= I_WILL_FREE;
        spin_unlock(&inode->i_lock);
        write_inode_now(inode, 1);
        spin_lock(&inode->i_lock);
        WARN_ON(inode->i_state & I_NEW);
        inode->i_state &= ~I_WILL_FREE;
    }

    inode->i_state |= I_FREEING;
    if (!list_empty(&inode->i_lru))
        inode_lru_list_del(inode);
    spin_unlock(&inode->i_lock);

    evict(inode);
}

void iput(struct inode *inode)
{
    if (inode) {
        BUG_ON(inode->i_state & I_CLEAR);

        if (atomic_dec_and_lock(&inode->i_count, &inode->i_lock))
            iput_final(inode);
    }
}
EXPORT_SYMBOL(iput);

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);

/*
 * With relative atime, only update atime if the previous atime is
 * earlier than either the ctime or mtime or if at least a day has
 * passed since the last atime update.
 */
static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
                 struct timespec now)
{

    if (!(mnt->mnt_flags & MNT_RELATIME))
        return 1;
    /*
     * Is mtime younger than atime? If yes, update atime:
     */
    if (timespec_compare(&inode->i_mtime, &inode->i_atime) >= 0)
        return 1;
    /*
     * Is ctime younger than atime? If yes, update atime:
     */
    if (timespec_compare(&inode->i_ctime, &inode->i_atime) >= 0)
        return 1;

    /*
     * Is the previous atime value older than a day? If yes,
     * update atime:
     */
    if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
        return 1;
    /*
     * Good, we can skip the atime update:
     */
    return 0;
}

/*
 * This does the actual work of updating an inodes time or version.  Must have
 * had called mnt_want_write() before calling this.
 */
static int update_time(struct inode *inode, struct timespec *time, int flags)
{
    if (inode->i_op->update_time)
        return inode->i_op->update_time(inode, time, flags);

    if (flags & S_ATIME)
        inode->i_atime = *time;
    if (flags & S_VERSION)
        inode_inc_iversion(inode);
    if (flags & S_CTIME)
        inode->i_ctime = *time;
    if (flags & S_MTIME)
        inode->i_mtime = *time;
    mark_inode_dirty_sync(inode);
    return 0;
}

void touch_atime(struct path *path)
{
    struct vfsmount *mnt = path->mnt;
    struct inode *inode = path->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;

    if (mnt->mnt_flags & MNT_NOATIME)
        return;
    if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
        return;

    now = current_fs_time(inode->i_sb);

    if (!relatime_need_update(mnt, inode, now))
        return;

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

    if (!sb_start_write_trylock(inode->i_sb))
        return;

    if (__mnt_want_write(mnt))
        goto skip_update;
    /*
     * File systems can error out when updating inodes if they need to
     * allocate new space to modify an inode (such is the case for
     * Btrfs), but since we touch atime while walking down the path we
     * really don't care if we failed to update the atime of the file,
     * so just ignore the return value.
     * We may also fail on filesystems that have the ability to make parts
     * of the fs read only, e.g. subvolumes in Btrfs.
     */
    update_time(inode, &now, S_ATIME);
    __mnt_drop_write(mnt);
skip_update:
    sb_end_write(inode->i_sb);
}
EXPORT_SYMBOL(touch_atime);

/*
 * The logic we want is
 *
 *  if suid or (sgid and xgrp)
 *      remove privs
 */
int should_remove_suid(struct dentry *dentry)
{
    umode_t mode = dentry->d_inode->i_mode;
    int kill = 0;

    /* suid always must be killed */
    if (unlikely(mode & S_ISUID))
        kill = ATTR_KILL_SUID;

    /*
     * sgid without any exec bits is just a mandatory locking mark; leave
     * it alone.  If some exec bits are set, it's a real sgid; kill it.
     */
    if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
        kill |= ATTR_KILL_SGID;

    if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
        return kill;

    return 0;
}
EXPORT_SYMBOL(should_remove_suid);

static int __remove_suid(struct dentry *dentry, int kill)
{
    struct iattr newattrs;

    newattrs.ia_valid = ATTR_FORCE | kill;
    return notify_change(dentry, &newattrs);
}

int file_remove_suid(struct file *file)
{
    struct dentry *dentry = file->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    int killsuid;
    int killpriv;
    int error = 0;

    /* Fast path for nothing security related */
    if (IS_NOSEC(inode))
        return 0;

    killsuid = should_remove_suid(dentry);
    killpriv = security_inode_need_killpriv(dentry);

    if (killpriv < 0)
        return killpriv;
    if (killpriv)
        error = security_inode_killpriv(dentry);
    if (!error && killsuid)
        error = __remove_suid(dentry, killsuid);
    if (!error && (inode->i_sb->s_flags & MS_NOSEC))
        inode->i_flags |= S_NOSEC;

    return error;
}
EXPORT_SYMBOL(file_remove_suid);

int file_update_time(struct file *file)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct timespec now;
    int sync_it = 0;
    int ret;

    /* First try to exhaust all avenues to not sync */
    if (IS_NOCMTIME(inode))
        return 0;

    now = current_fs_time(inode->i_sb);
    if (!timespec_equal(&inode->i_mtime, &now))
        sync_it = S_MTIME;

    if (!timespec_equal(&inode->i_ctime, &now))
        sync_it |= S_CTIME;

    if (IS_I_VERSION(inode))
        sync_it |= S_VERSION;

    if (!sync_it)
        return 0;

    /* Finally allowed to write? Takes lock. */
    if (__mnt_want_write_file(file))
        return 0;

    ret = update_time(inode, &now, sync_it);
    __mnt_drop_write_file(file);

    return ret;
}
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;
}
EXPORT_SYMBOL(inode_wait);

/*
 * 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_NEW is not set initially, a call to
 * wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list
 * will DTRT.
 */
static void __wait_on_freeing_inode(struct inode *inode)
{
    wait_queue_head_t *wq;
    DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
    wq = bit_waitqueue(&inode->i_state, __I_NEW);
    prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
    spin_unlock(&inode->i_lock);
    spin_unlock(&inode_hash_lock);
    schedule();
    finish_wait(wq, &wait.wait);
    spin_lock(&inode_hash_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)
{
    unsigned 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,
                    0);

    for (loop = 0; loop < (1U << i_hash_shift); loop++)
        INIT_HLIST_HEAD(&inode_hashtable[loop]);
}

void __init inode_init(void)
{
    unsigned 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);

    /* 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,
                    0);

    for (loop = 0; loop < (1U << 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) for"
                  " inode %s:%lu\n", mode, inode->i_sb->s_id,
                  inode->i_ino);
}
EXPORT_SYMBOL(init_special_inode);

void inode_init_owner(struct inode *inode, const struct inode *dir,
            umode_t mode)
{
    inode->i_uid = current_fsuid();
    if (dir && dir->i_mode & S_ISGID) {
        inode->i_gid = dir->i_gid;
        if (S_ISDIR(mode))
            mode |= S_ISGID;
    } else
        inode->i_gid = current_fsgid();
    inode->i_mode = mode;
}
EXPORT_SYMBOL(inode_init_owner);

bool inode_owner_or_capable(const struct inode *inode)
{
    if (uid_eq(current_fsuid(), inode->i_uid))
        return true;
    if (inode_capable(inode, CAP_FOWNER))
        return true;
    return false;
}
EXPORT_SYMBOL(inode_owner_or_capable);

/*
 * Direct i/o helper functions
 */
static void __inode_dio_wait(struct inode *inode)
{
    wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
    DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);

    do {
        prepare_to_wait(wq, &q.wait, TASK_UNINTERRUPTIBLE);
        if (atomic_read(&inode->i_dio_count))
            schedule();
    } while (atomic_read(&inode->i_dio_count));
    finish_wait(wq, &q.wait);
}

void inode_dio_wait(struct inode *inode)
{
    if (atomic_read(&inode->i_dio_count))
        __inode_dio_wait(inode);
}
EXPORT_SYMBOL(inode_dio_wait);

/*
 * inode_dio_done - signal finish of a direct I/O requests
 * @inode: inode the direct I/O happens on
 *
 * This is called once we've finished processing a direct I/O request,
 * and is used to wake up callers waiting for direct I/O to be quiesced.
 */
void inode_dio_done(struct inode *inode)
{
    if (atomic_dec_and_test(&inode->i_dio_count))
        wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
}
EXPORT_SYMBOL(inode_dio_done);