Import 2.3.26pre2

[davej-history.git] / fs / inode.c

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

#include <linux/fs.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/dcache.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/slab.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 HASH_BITS       14
#define HASH_SIZE       (1UL << HASH_BITS)
#define HASH_MASK       (HASH_SIZE-1)

/*
 * 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.
 */

static LIST_HEAD(inode_in_use);
static LIST_HEAD(inode_unused);
static struct list_head inode_hashtable[HASH_SIZE];

/*
 * 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..
 */
spinlock_t inode_lock = SPIN_LOCK_UNLOCKED;

/*
 * Statistics gathering..
 */
struct {
        int nr_inodes;
        int nr_unused;
        int dummy[5];
} inodes_stat = {0, 0,};

static kmem_cache_t * inode_cachep;

#define alloc_inode() \
         ((struct inode *) kmem_cache_alloc(inode_cachep, SLAB_KERNEL))
#define destroy_inode(inode) 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.
 */
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)
        {
                memset(inode, 0, sizeof(*inode));
                init_waitqueue_head(&inode->i_wait);
                INIT_LIST_HEAD(&inode->i_hash);
                INIT_LIST_HEAD(&inode->i_data.pages);
                INIT_LIST_HEAD(&inode->i_dentry);
                sema_init(&inode->i_sem, 1);
                spin_lock_init(&inode->i_shared_lock);
        }
}

/*
 * Put the inode on the super block's dirty list.
 *
 * CAREFUL! We mark it dirty unconditionally, but
 * move it onto the dirty list only if it is hashed.
 * If it was not hashed, it will never be added to
 * the dirty list even if it is later hashed, as it
 * will have been marked dirty already.
 *
 * In short, make sure you hash any inodes _before_
 * you start marking them dirty..
 */
void __mark_inode_dirty(struct inode *inode)
{
        struct super_block * sb = inode->i_sb;

        if (sb) {
                spin_lock(&inode_lock);
                if (!(inode->i_state & I_DIRTY)) {
                        inode->i_state |= I_DIRTY;
                        /* Only add valid (ie hashed) inodes to the dirty list */
                        if (!list_empty(&inode->i_hash)) {
                                list_del(&inode->i_list);
                                list_add(&inode->i_list, &sb->s_dirty);
                        }
                }
                spin_unlock(&inode_lock);
        }
}

static void __wait_on_inode(struct inode * inode)
{
        DECLARE_WAITQUEUE(wait, current);

        add_wait_queue(&inode->i_wait, &wait);
repeat:
        set_current_state(TASK_UNINTERRUPTIBLE);
        if (inode->i_state & I_LOCK) {
                schedule();
                goto repeat;
        }
        remove_wait_queue(&inode->i_wait, &wait);
        current->state = TASK_RUNNING;
}

static inline void wait_on_inode(struct inode *inode)
{
        if (inode->i_state & I_LOCK)
                __wait_on_inode(inode);
}


static inline void write_inode(struct inode *inode)
{
        if (inode->i_sb && inode->i_sb->s_op && inode->i_sb->s_op->write_inode)
                inode->i_sb->s_op->write_inode(inode);
}

static inline void sync_one(struct inode *inode)
{
        if (inode->i_state & I_LOCK) {
                spin_unlock(&inode_lock);
                __wait_on_inode(inode);
                spin_lock(&inode_lock);
        } else {
                list_del(&inode->i_list);
                list_add(&inode->i_list,
                         inode->i_count ? &inode_in_use : &inode_unused);
                /* Set I_LOCK, reset I_DIRTY */
                inode->i_state ^= I_DIRTY | I_LOCK;
                spin_unlock(&inode_lock);

                write_inode(inode);

                spin_lock(&inode_lock);
                inode->i_state &= ~I_LOCK;
                wake_up(&inode->i_wait);
        }
}

static inline void sync_list(struct list_head *head)
{
        struct list_head * tmp;

        while ((tmp = head->prev) != head)
                sync_one(list_entry(tmp, struct inode, i_list));
}

/*
 * "sync_inodes()" goes through the super block's dirty list, 
 * writes them out, and puts them back on the normal list.
 */
void sync_inodes(kdev_t dev)
{
        struct super_block * sb = sb_entry(super_blocks.next);

        /*
         * Search the super_blocks array for the device(s) to sync.
         */
        spin_lock(&inode_lock);
        for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.next)) {
                if (!sb->s_dev)
                        continue;
                if (dev && sb->s_dev != dev)
                        continue;

                sync_list(&sb->s_dirty);

                if (dev)
                        break;
        }
        spin_unlock(&inode_lock);
}

/*
 * Called with the spinlock already held..
 */
static void sync_all_inodes(void)
{
        struct super_block * sb = sb_entry(super_blocks.next);
        for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.next)) {
                if (!sb->s_dev)
                        continue;
                sync_list(&sb->s_dirty);
        }
}

/*
 * Needed by knfsd
 */
void write_inode_now(struct inode *inode)
{
        struct super_block * sb = inode->i_sb;

        if (sb) {
                spin_lock(&inode_lock);
                while (inode->i_state & I_DIRTY)
                        sync_one(inode);
                spin_unlock(&inode_lock);
        }
        else
                printk("write_inode_now: no super block\n");
}

/*
 * 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)
{
        if (inode->i_data.nrpages)
                BUG();
        if (!(inode->i_state & I_FREEING))
                BUG();
        wait_on_inode(inode);
        if (IS_QUOTAINIT(inode))
                DQUOT_DROP(inode);
        if (inode->i_sb && inode->i_sb->s_op && inode->i_sb->s_op->clear_inode)
                inode->i_sb->s_op->clear_inode(inode);

        inode->i_state = 0;
}

/*
 * 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)
{
        struct list_head * inode_entry;
        struct inode * inode;

        while ((inode_entry = head->next) != head)
        {
                list_del(inode_entry);

                inode = list_entry(inode_entry, struct inode, i_list);
                if (inode->i_data.nrpages)
                        truncate_inode_pages(inode, 0);
                clear_inode(inode);
                destroy_inode(inode);
        }
}

/*
 * Invalidate all inodes for a device.
 */
static int invalidate_list(struct list_head *head, struct super_block * sb, 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;

                next = next->next;
                if (tmp == head)
                        break;
                inode = list_entry(tmp, struct inode, i_list);
                if (inode->i_sb != sb)
                        continue;
                if (!inode->i_count) {
                        list_del(&inode->i_hash);
                        INIT_LIST_HEAD(&inode->i_hash);
                        list_del(&inode->i_list);
                        list_add(&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..
 */
int invalidate_inodes(struct super_block * sb)
{
        int busy;
        LIST_HEAD(throw_away);

        spin_lock(&inode_lock);
        busy = invalidate_list(&inode_in_use, sb, &throw_away);
        busy |= invalidate_list(&inode_unused, sb, &throw_away);
        busy |= invalidate_list(&sb->s_dirty, sb, &throw_away);
        spin_unlock(&inode_lock);

        dispose_list(&throw_away);

        return busy;
}

/*
 * This is called with the inode lock held. It searches
 * the in-use for freeable inodes, which are moved to a
 * temporary list and then placed on the unused list by
 * dispose_list. 
 *
 * We don't expect to have to call this very often.
 *
 * N.B. The spinlock is released during the call to
 *      dispose_list.
 */
#define CAN_UNUSE(inode) \
        (((inode)->i_state | (inode)->i_data.nrpages) == 0)
#define INODE(entry)    (list_entry(entry, struct inode, i_list))

void prune_icache(int goal)
{
        LIST_HEAD(list);
        struct list_head *entry, *freeable = &list;
        int count = 0;
        struct inode * inode;

        spin_lock(&inode_lock);
        /* go simple and safe syncing everything before starting */
        sync_all_inodes();

        entry = inode_unused.prev;
        while (entry != &inode_unused)
        {
                struct list_head *tmp = entry;

                entry = entry->prev;
                inode = INODE(tmp);
                if (!CAN_UNUSE(inode))
                        continue;
                if (inode->i_count)
                        BUG();
                list_del(tmp);
                list_del(&inode->i_hash);
                INIT_LIST_HEAD(&inode->i_hash);
                list_add(tmp, freeable);
                inode->i_state |= I_FREEING;
                count++;
                if (!--goal)
                        break;
        }
        inodes_stat.nr_unused -= count;
        spin_unlock(&inode_lock);

        dispose_list(freeable);
}

int shrink_icache_memory(int priority, int gfp_mask)
{
        if (gfp_mask & __GFP_IO)
        {
                int count = 0;
                
                if (priority)
                        count = inodes_stat.nr_unused / priority;
                prune_icache(count);
                /* FIXME: kmem_cache_shrink here should tell us
                   the number of pages freed, and it should
                   work in a __GFP_DMA/__GFP_HIGHMEM behaviour
                   to free only the interesting pages in
                   function of the needs of the current allocation. */
                kmem_cache_shrink(inode_cachep);
        }

        return 0;
}

static inline void __iget(struct inode * inode)
{
        if (!inode->i_count++)
        {
                if (!(inode->i_state & I_DIRTY))
                {
                        list_del(&inode->i_list);
                        list_add(&inode->i_list, &inode_in_use);
                }
                inodes_stat.nr_unused--;
        }
}

/*
 * 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 simplify iunique and won't
 * add any additional branch in the common code.
 */
static struct inode * find_inode(struct super_block * sb, unsigned long ino, struct list_head *head, find_inode_t find_actor, void *opaque)
{
        struct list_head *tmp;
        struct inode * inode;

        tmp = head;
        for (;;) {
                tmp = tmp->next;
                inode = NULL;
                if (tmp == head)
                        break;
                inode = list_entry(tmp, struct inode, i_hash);
                if (inode->i_sb != sb)
                        continue;
                if (inode->i_ino != ino)
                        continue;
                if (find_actor && !find_actor(inode, ino, opaque))
                        continue;
                break;
        }
        return inode;
}

/*
 * This just initializes the inode fields
 * to known values before returning the inode..
 *
 * i_sb, i_ino, i_count, i_state and the lists have
 * been initialized elsewhere..
 */
static void clean_inode(struct inode *inode)
{
        memset(&inode->u, 0, sizeof(inode->u));
        inode->i_sock = 0;
        inode->i_op = NULL;
        inode->i_nlink = 1;
        atomic_set(&inode->i_writecount, 0);
        inode->i_size = 0;
        inode->i_generation = 0;
        memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
        inode->i_pipe = NULL;
}

/*
 * This is called by things like the networking layer
 * etc that want to get an inode without any inode
 * number, or filesystems that allocate new inodes with
 * no pre-existing information.
 */
struct inode * get_empty_inode(void)
{
        static unsigned long last_ino = 0;
        struct inode * inode;

        inode = alloc_inode();
        if (inode)
        {
                spin_lock(&inode_lock);
                list_add(&inode->i_list, &inode_in_use);
                inode->i_sb = NULL;
                inode->i_dev = 0;
                inode->i_ino = ++last_ino;
                inode->i_flags = 0;
                inode->i_count = 1;
                inode->i_state = 0;
                spin_unlock(&inode_lock);
                clean_inode(inode);
        }
        return 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, unsigned long ino, struct list_head *head, find_inode_t find_actor, void *opaque)
{
        struct inode * inode;

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

                spin_lock(&inode_lock);
                /* We released the lock, so.. */
                old = find_inode(sb, ino, head, find_actor, opaque);
                if (!old) {
                        list_add(&inode->i_list, &inode_in_use);
                        list_add(&inode->i_hash, head);
                        inode->i_sb = sb;
                        inode->i_dev = sb->s_dev;
                        inode->i_ino = ino;
                        inode->i_flags = 0;
                        inode->i_count = 1;
                        inode->i_state = I_LOCK;
                        spin_unlock(&inode_lock);

                        clean_inode(inode);
                        sb->s_op->read_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;
                        wake_up(&inode->i_wait);

                        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 i_ino)
{
        unsigned long tmp = i_ino | (unsigned long) sb;
        tmp = tmp + (tmp >> HASH_BITS) + (tmp >> HASH_BITS*2);
        return tmp & HASH_MASK;
}

/* Yeah, I know about quadratic hash. Maybe, later. */
ino_t iunique(struct super_block *sb, ino_t max_reserved)
{
        static ino_t counter = 0;
        struct inode *inode;
        struct list_head * head;
        ino_t res;
        spin_lock(&inode_lock);
retry:
        if (counter > max_reserved) {
                head = inode_hashtable + hash(sb,counter);
                inode = find_inode(sb, res = counter++, head, NULL, NULL);
                if (!inode) {
                        spin_unlock(&inode_lock);
                        return res;
                }
        } else {
                counter = max_reserved + 1;
        }
        goto retry;
        
}

struct inode *igrab(struct inode *inode)
{
        spin_lock(&inode_lock);
        if (!(inode->i_state & I_FREEING))
                __iget(inode);
        else
                inode = NULL;
        spin_unlock(&inode_lock);
        if (inode)
                wait_on_inode(inode);
        return inode;
}

struct inode *iget4(struct super_block *sb, unsigned long ino, find_inode_t find_actor, void *opaque)
{
        struct list_head * head = inode_hashtable + hash(sb,ino);
        struct inode * inode;

        spin_lock(&inode_lock);
        inode = find_inode(sb, ino, head, find_actor, opaque);
        if (inode) {
                __iget(inode);
                spin_unlock(&inode_lock);
                wait_on_inode(inode);
                return inode;
        }
        spin_unlock(&inode_lock);

        /*
         * 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, ino, head, find_actor, opaque);
}

void insert_inode_hash(struct inode *inode)
{
        struct list_head *head = inode_hashtable + hash(inode->i_sb, inode->i_ino);
        spin_lock(&inode_lock);
        list_add(&inode->i_hash, head);
        spin_unlock(&inode_lock);
}

void remove_inode_hash(struct inode *inode)
{
        spin_lock(&inode_lock);
        list_del(&inode->i_hash);
        INIT_LIST_HEAD(&inode->i_hash);
        spin_unlock(&inode_lock);
}

void iput(struct inode *inode)
{
        if (inode) {
                struct super_operations *op = NULL;
                int destroy = 0;

                if (inode->i_sb && inode->i_sb->s_op)
                        op = inode->i_sb->s_op;
                if (op && op->put_inode)
                        op->put_inode(inode);

                spin_lock(&inode_lock);
                if (!--inode->i_count) {
                        if (!inode->i_nlink) {
                                list_del(&inode->i_hash);
                                INIT_LIST_HEAD(&inode->i_hash);
                                list_del(&inode->i_list);
                                INIT_LIST_HEAD(&inode->i_list);
                                inode->i_state|=I_FREEING;
                                if (op && op->delete_inode) {
                                        void (*delete)(struct inode *) = op->delete_inode;
                                        spin_unlock(&inode_lock);
                                        if (inode->i_data.nrpages)
                                                truncate_inode_pages(inode, 0);
                                        delete(inode);
                                        spin_lock(&inode_lock);
                                }
                        }
                        if (list_empty(&inode->i_hash)) {
                                list_del(&inode->i_list);
                                INIT_LIST_HEAD(&inode->i_list);
                                inode->i_state|=I_FREEING;
                                spin_unlock(&inode_lock);
                                clear_inode(inode);
                                destroy = 1;
                                spin_lock(&inode_lock);
                        }
                        else
                        {
                                if (!(inode->i_state & I_DIRTY)) {
                                        list_del(&inode->i_list);
                                        list_add(&inode->i_list,
                                                 &inode_unused);
                                }
                                inodes_stat.nr_unused++;
                        }
#ifdef INODE_PARANOIA
if (inode->i_flock)
printk(KERN_ERR "iput: inode %s/%ld still has locks!\n",
kdevname(inode->i_dev), inode->i_ino);
if (!list_empty(&inode->i_dentry))
printk(KERN_ERR "iput: device %s inode %ld still has aliases!\n",
kdevname(inode->i_dev), inode->i_ino);
if (inode->i_count)
printk(KERN_ERR "iput: device %s inode %ld count changed, count=%d\n",
kdevname(inode->i_dev), inode->i_ino, inode->i_count);
if (atomic_read(&inode->i_sem.count) != 1)
printk(KERN_ERR "iput: Aieee, semaphore in use inode %s/%ld, count=%d\n",
kdevname(inode->i_dev), inode->i_ino, atomic_read(&inode->i_sem.count));
#endif
                }
                if (inode->i_count > (1<<31)) {
                        printk(KERN_ERR "iput: inode %s/%ld count wrapped\n",
                                kdevname(inode->i_dev), inode->i_ino);
                }
                spin_unlock(&inode_lock);
                if (destroy)
                        destroy_inode(inode);
        }
}

int bmap(struct inode * inode, int block)
{
        struct buffer_head tmp;

        if (inode->i_op && inode->i_op->get_block) {
                tmp.b_state = 0;
                tmp.b_blocknr = 0;
                inode->i_op->get_block(inode, block, &tmp, 0);
                return tmp.b_blocknr;
        }
        return 0;
}

/*
 * Initialize the hash tables.
 */
void __init inode_init(void)
{
        int i;
        struct list_head *head = inode_hashtable;

        i = HASH_SIZE;
        do {
                INIT_LIST_HEAD(head);
                head++;
                i--;
        } while (i);

        /* inode slab cache */
        inode_cachep = kmem_cache_create("inode_cache", sizeof(struct inode),
                                         0, SLAB_HWCACHE_ALIGN, init_once,
                                         NULL);
        if (!inode_cachep)
                panic("cannot create inode slab cache");
}

void update_atime (struct inode *inode)
{
    if ( IS_NOATIME (inode) ) return;
    if ( IS_NODIRATIME (inode) && S_ISDIR (inode->i_mode) ) return;
    if ( IS_RDONLY (inode) ) return;
    inode->i_atime = CURRENT_TIME;
    mark_inode_dirty (inode);
}   /*  End Function update_atime  */