Software of the Month Club 2000 October/Software of the Month - Ultimate Collection Shareware 277.iso/pc/PROGRAMS/UTILITY/WINLINUX/DATA1.CAB/programs_-_kernel_source/FS/INODE.C

C/C++ Source or Header | 1999-09-17 | 18.6 KB | 807 lines

/*
 * 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>

/*
 * 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.
 */

#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    8
#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, hashed if i_nlink > 0
 *  "dirty"  - valid inode, hashed if i_nlink > 0, dirty.
 *  "unused" - ready to be re-used. Not hashed.
 *
 * 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_free_inodes;
    int dummy[5];
} inodes_stat = {0, 0,};

int max_inodes;

/*
 * 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)
{
    struct wait_queue wait = { current, NULL };

    add_wait_queue(&inode->i_wait, &wait);
repeat:
    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);
}

/*
 * These are initializations that only need to be done
 * once, because the fields are idempotent across use
 * of the inode..
 */
static inline void init_once(struct inode * inode)
{
    memset(inode, 0, sizeof(*inode));
    init_waitqueue(&inode->i_wait);
    INIT_LIST_HEAD(&inode->i_hash);
    INIT_LIST_HEAD(&inode->i_dentry);
    sema_init(&inode->i_sem, 1);
    sema_init(&inode->i_atomic_write, 1);
}

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_in_use);
        /* 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_nrpages)
        truncate_inode_pages(inode, 0);
    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, so it doesn't need to
 * worry about list corruption. It releases the inode lock
 * while clearing the inodes.
 */
static void dispose_list(struct list_head * head)
{
    struct list_head *next;
    int count = 0;

    spin_unlock(&inode_lock);
    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);
        clear_inode(inode);
        count++;
    }

    /* Add them all to the unused list in one fell swoop */
    spin_lock(&inode_lock);
    list_splice(head, &inode_unused);
    inodes_stat.nr_free_inodes += count;
}

/*
 * 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;

    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);
            continue;
        }
        busy = 1;
    }
    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(&sb->s_dirty, sb, &throw_away);
    dispose_list(&throw_away);
    spin_unlock(&inode_lock);

    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_count | (inode)->i_state) == 0)
#define INODE(entry)    (list_entry(entry, struct inode, i_list))

static int free_inodes(void)
{
    struct list_head list, *entry, *freeable = &list;
    int found = 0;

    INIT_LIST_HEAD(freeable);
    entry = inode_in_use.next;
    while (entry != &inode_in_use) {
        struct list_head *tmp = entry;

        entry = entry->next;
        if (!CAN_UNUSE(INODE(tmp)))
            continue;
        list_del(tmp);
        list_del(&INODE(tmp)->i_hash);
        INIT_LIST_HEAD(&INODE(tmp)->i_hash);
        list_add(tmp, freeable);
        found = 1;
    }

    if (found) {
        dispose_list(freeable);
        found = 1;    /* silly compiler */
    }

    return found;
}

/*
 * Searches the inodes list for freeable inodes,
 * shrinking the dcache before (and possible after,
 * if we're low)
 */
static void try_to_free_inodes(int goal)
{
    /*
     * First stry to just get rid of unused inodes.
     *
     * If we can't reach our goal that way, we'll have
     * to try to shrink the dcache and sync existing
     * inodes..
     */
    free_inodes();
    goal -= inodes_stat.nr_free_inodes;
    if (goal > 0) {
        spin_unlock(&inode_lock);
        select_dcache(goal, 0);
        prune_dcache(goal);
        spin_lock(&inode_lock);
        sync_all_inodes();
        free_inodes();
    }
}

/*
 * This is the externally visible routine for
 * inode memory management.
 */
void free_inode_memory(int goal)
{
    spin_lock(&inode_lock);
    free_inodes();
    spin_unlock(&inode_lock);
}


/*
 * This is called with the spinlock held, but releases
 * the lock when freeing or allocating inodes.
 * Look out! This returns with the inode lock held if
 * it got an inode..
 *
 * We do inode allocations two pages at a time to reduce
 * fragmentation.
 */
#define INODE_PAGE_ORDER    1
#define INODE_ALLOCATION_SIZE    (PAGE_SIZE << INODE_PAGE_ORDER)
#define INODES_PER_ALLOCATION    (INODE_ALLOCATION_SIZE/sizeof(struct inode))

static struct inode * grow_inodes(void)
{
    struct inode * inode;

    /*
     * Check whether to restock the unused list.
     */
    if (inodes_stat.nr_inodes > max_inodes) {
        struct list_head *tmp;
        try_to_free_inodes(inodes_stat.nr_inodes >> 2);
        tmp = inode_unused.next;
        if (tmp != &inode_unused) {
            inodes_stat.nr_free_inodes--;
            list_del(tmp);
            inode = list_entry(tmp, struct inode, i_list);
            return inode;
        }
    }

    spin_unlock(&inode_lock);
    inode = (struct inode *)__get_free_pages(GFP_KERNEL,INODE_PAGE_ORDER);
    if (inode) {
        int size;
        struct inode * tmp;

        size = INODE_ALLOCATION_SIZE - 2*sizeof(struct inode);
        tmp = inode;
        spin_lock(&inode_lock);
        do {
            tmp++;
            init_once(tmp);
            list_add(&tmp->i_list, &inode_unused);
            size -= sizeof(struct inode);
        } while (size >= 0);
        init_once(inode);
        /*
         * Update the inode statistics
         */
        inodes_stat.nr_inodes += INODES_PER_ALLOCATION;
        inodes_stat.nr_free_inodes += INODES_PER_ALLOCATION - 1;
        return inode;
    }

    /*
     * If the allocation failed, do an extensive pruning of
     * the dcache and then try again to free some inodes.
     */
    prune_dcache(inodes_stat.nr_inodes >> 2);

    spin_lock(&inode_lock);
    free_inodes();
    {
        struct list_head *tmp = inode_unused.next;
        if (tmp != &inode_unused) {
            inodes_stat.nr_free_inodes--;
            list_del(tmp);
            inode = list_entry(tmp, struct inode, i_list);
            return inode;
        }
    }
    spin_unlock(&inode_lock);

    printk("grow_inodes: allocation failed\n");
    return NULL;
}

/*
 * Called with the inode lock held.
 */
static struct inode * find_inode(struct super_block * sb, unsigned long ino, struct list_head *head)
{
    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;
        inode->i_count++;
        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..
 */
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;
    inode->i_writecount = 0;
    inode->i_size = 0;
    memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
    sema_init(&inode->i_sem, 1);
}

/*
 * 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;
    struct list_head * tmp;

    spin_lock(&inode_lock);
    tmp = inode_unused.next;
    if (tmp != &inode_unused) {
        list_del(tmp);
        inodes_stat.nr_free_inodes--;
        inode = list_entry(tmp, struct inode, i_list);
add_new_inode:
        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;
    }

    /*
     * Warning: if this succeeded, we will now
     * return with the inode lock.
     */
    inode = grow_inodes();
    if (inode)
        goto add_new_inode;

    return inode;
}

/*
 * This is called with the inode lock held.. Be careful.
 *
 * We no longer cache the sb_flags in i_flags - see fs.h
 *    -- [e-mail]
 */
static struct inode * get_new_inode(struct super_block *sb, unsigned long ino, struct list_head *head)
{
    struct inode * inode;
    struct list_head * tmp = inode_unused.next;

    if (tmp != &inode_unused) {
        list_del(tmp);
        inodes_stat.nr_free_inodes--;
        inode = list_entry(tmp, struct inode, i_list);
add_new_inode:
        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;
    }

    /*
     * We need to expand. Note that "grow_inodes()" will
     * release the spinlock, but will return with the lock
     * held again if the allocation succeeded.
     */
    inode = grow_inodes();
    if (inode) {
        /* We released the lock, so.. */
        struct inode * old = find_inode(sb, ino, head);
        if (!old)
            goto add_new_inode;
        list_add(&inode->i_list, &inode_unused);
        inodes_stat.nr_free_inodes++;
        spin_unlock(&inode_lock);
        wait_on_inode(old);
        return old;
    }
    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;
}

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

    spin_lock(&inode_lock);
    inode = find_inode(sb, ino, head);
    if (inode) {
        spin_unlock(&inode_lock);
        wait_on_inode(inode);
        return inode;
    }
    /*
     * get_new_inode() will do the right thing, releasing
     * the inode lock and re-trying the search in case it
     * had to block at any point.
     */
    return get_new_inode(sb, ino, head);
}

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;

        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);
                if (op && op->delete_inode) {
                    void (*delete)(struct inode *) = op->delete_inode;
                    spin_unlock(&inode_lock);
                    delete(inode);
                    spin_lock(&inode_lock);
                }
            }
            if (list_empty(&inode->i_hash)) {
                list_del(&inode->i_list);
                INIT_LIST_HEAD(&inode->i_list);
                spin_unlock(&inode_lock);
                clear_inode(inode);
                spin_lock(&inode_lock);
                list_add(&inode->i_list, &inode_unused);
                inodes_stat.nr_free_inodes++;
            }
            else if (!(inode->i_state & I_DIRTY)) {
                list_del(&inode->i_list);
                list_add(&inode->i_list, &inode_in_use);
            }
#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));
if (atomic_read(&inode->i_atomic_write.count) != 1)
printk(KERN_ERR "iput: Aieee, atomic write 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);
    }
}

int bmap(struct inode * inode, int block)
{
    if (inode->i_op && inode->i_op->bmap)
        return inode->i_op->bmap(inode, block);
    return 0;
}

/*
 * Initialize the hash tables and default
 * value for max inodes
 */
#define MAX_INODE (12288)

void __init inode_init(void)
{
    int i, max;
    struct list_head *head = inode_hashtable;

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

    /* Initial guess at reasonable inode number */
    max = num_physpages >> 1;
    if (max > MAX_INODE)
        max = MAX_INODE;
    max_inodes = max;
}

/* This belongs in file_table.c, not here... */
int fs_may_remount_ro(struct super_block *sb)
{
    struct file *file;

    /* Check that no files are currently opened for writing. */
    for (file = inuse_filps; file; file = file->f_next) {
        struct inode *inode;
        if (!file->f_dentry)
            continue;
        inode = file->f_dentry->d_inode;
        if (!inode || inode->i_sb != sb)
            continue;

        /* File with pending delete? */
        if (inode->i_nlink == 0)
            return 0;

        /* Writable file? */
        if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
            return 0;
    }
    return 1; /* Tis' cool bro. */
}

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  */