ialloc.c

Go to the documentation of this file.

/*
 *  linux/fs/ext2/ialloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  BSD ufs-inspired inode and directory allocation by 
 *  Stephen Tweedie ([email protected]), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 */

#include <linux/quotaops.h>
#include <linux/sched.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/random.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"

/*
 * ialloc.c contains the inodes allocation and deallocation routines
 */

/*
 * The free inodes are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.
 */


/*
 * Read the inode allocation bitmap for a given block_group, reading
 * into the specified slot in the superblock's bitmap cache.
 *
 * Return buffer_head of bitmap on success or NULL.
 */
static struct buffer_head *
read_inode_bitmap(struct super_block * sb, unsigned long block_group)
{
    struct ext2_group_desc *desc;
    struct buffer_head *bh = NULL;

    desc = ext2_get_group_desc(sb, block_group, NULL);
    if (!desc)
        goto error_out;

    bh = sb_bread(sb, le32_to_cpu(desc->bg_inode_bitmap));
    if (!bh)
        ext2_error(sb, "read_inode_bitmap",
                "Cannot read inode bitmap - "
                "block_group = %lu, inode_bitmap = %u",
                block_group, le32_to_cpu(desc->bg_inode_bitmap));
error_out:
    return bh;
}

static void ext2_release_inode(struct super_block *sb, int group, int dir)
{
    struct ext2_group_desc * desc;
    struct buffer_head *bh;

    desc = ext2_get_group_desc(sb, group, &bh);
    if (!desc) {
        ext2_error(sb, "ext2_release_inode",
            "can't get descriptor for group %d", group);
        return;
    }

    spin_lock(sb_bgl_lock(EXT2_SB(sb), group));
    le16_add_cpu(&desc->bg_free_inodes_count, 1);
    if (dir)
        le16_add_cpu(&desc->bg_used_dirs_count, -1);
    spin_unlock(sb_bgl_lock(EXT2_SB(sb), group));
    if (dir)
        percpu_counter_dec(&EXT2_SB(sb)->s_dirs_counter);
    mark_buffer_dirty(bh);
}

/*
 * NOTE! When we get the inode, we're the only people
 * that have access to it, and as such there are no
 * race conditions we have to worry about. The inode
 * is not on the hash-lists, and it cannot be reached
 * through the filesystem because the directory entry
 * has been deleted earlier.
 *
 * HOWEVER: we must make sure that we get no aliases,
 * which means that we have to call "clear_inode()"
 * _before_ we mark the inode not in use in the inode
 * bitmaps. Otherwise a newly created file might use
 * the same inode number (not actually the same pointer
 * though), and then we'd have two inodes sharing the
 * same inode number and space on the harddisk.
 */
void ext2_free_inode (struct inode * inode)
{
    struct super_block * sb = inode->i_sb;
    int is_directory;
    unsigned long ino;
    struct buffer_head *bitmap_bh;
    unsigned long block_group;
    unsigned long bit;
    struct ext2_super_block * es;

    ino = inode->i_ino;
    ext2_debug ("freeing inode %lu\n", ino);

    /*
     * Note: we must free any quota before locking the superblock,
     * as writing the quota to disk may need the lock as well.
     */
    /* Quota is already initialized in iput() */
    ext2_xattr_delete_inode(inode);
    dquot_free_inode(inode);
    dquot_drop(inode);

    es = EXT2_SB(sb)->s_es;
    is_directory = S_ISDIR(inode->i_mode);

    if (ino < EXT2_FIRST_INO(sb) ||
        ino > le32_to_cpu(es->s_inodes_count)) {
        ext2_error (sb, "ext2_free_inode",
                "reserved or nonexistent inode %lu", ino);
        return;
    }
    block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
    bit = (ino - 1) % EXT2_INODES_PER_GROUP(sb);
    bitmap_bh = read_inode_bitmap(sb, block_group);
    if (!bitmap_bh)
        return;

    /* Ok, now we can actually update the inode bitmaps.. */
    if (!ext2_clear_bit_atomic(sb_bgl_lock(EXT2_SB(sb), block_group),
                bit, (void *) bitmap_bh->b_data))
        ext2_error (sb, "ext2_free_inode",
                  "bit already cleared for inode %lu", ino);
    else
        ext2_release_inode(sb, block_group, is_directory);
    mark_buffer_dirty(bitmap_bh);
    if (sb->s_flags & MS_SYNCHRONOUS)
        sync_dirty_buffer(bitmap_bh);

    brelse(bitmap_bh);
}

/*
 * We perform asynchronous prereading of the new inode's inode block when
 * we create the inode, in the expectation that the inode will be written
 * back soon.  There are two reasons:
 *
 * - When creating a large number of files, the async prereads will be
 *   nicely merged into large reads
 * - When writing out a large number of inodes, we don't need to keep on
 *   stalling the writes while we read the inode block.
 *
 * FIXME: ext2_get_group_desc() needs to be simplified.
 */
static void ext2_preread_inode(struct inode *inode)
{
    unsigned long block_group;
    unsigned long offset;
    unsigned long block;
    struct ext2_group_desc * gdp;
    struct backing_dev_info *bdi;

    bdi = inode->i_mapping->backing_dev_info;
    if (bdi_read_congested(bdi))
        return;
    if (bdi_write_congested(bdi))
        return;

    block_group = (inode->i_ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
    gdp = ext2_get_group_desc(inode->i_sb, block_group, NULL);
    if (gdp == NULL)
        return;

    /*
     * Figure out the offset within the block group inode table
     */
    offset = ((inode->i_ino - 1) % EXT2_INODES_PER_GROUP(inode->i_sb)) *
                EXT2_INODE_SIZE(inode->i_sb);
    block = le32_to_cpu(gdp->bg_inode_table) +
                (offset >> EXT2_BLOCK_SIZE_BITS(inode->i_sb));
    sb_breadahead(inode->i_sb, block);
}

/*
 * There are two policies for allocating an inode.  If the new inode is
 * a directory, then a forward search is made for a block group with both
 * free space and a low directory-to-inode ratio; if that fails, then of
 * the groups with above-average free space, that group with the fewest
 * directories already is chosen.
 *
 * For other inodes, search forward from the parent directory\'s block
 * group to find a free inode.
 */
static int find_group_dir(struct super_block *sb, struct inode *parent)
{
    int ngroups = EXT2_SB(sb)->s_groups_count;
    int avefreei = ext2_count_free_inodes(sb) / ngroups;
    struct ext2_group_desc *desc, *best_desc = NULL;
    int group, best_group = -1;

    for (group = 0; group < ngroups; group++) {
        desc = ext2_get_group_desc (sb, group, NULL);
        if (!desc || !desc->bg_free_inodes_count)
            continue;
        if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
            continue;
        if (!best_desc || 
            (le16_to_cpu(desc->bg_free_blocks_count) >
             le16_to_cpu(best_desc->bg_free_blocks_count))) {
            best_group = group;
            best_desc = desc;
        }
    }
    if (!best_desc)
        return -1;

    return best_group;
}

/* 
 * Orlov's allocator for directories. 
 * 
 * We always try to spread first-level directories.
 *
 * If there are blockgroups with both free inodes and free blocks counts 
 * not worse than average we return one with smallest directory count. 
 * Otherwise we simply return a random group. 
 * 
 * For the rest rules look so: 
 * 
 * It's OK to put directory into a group unless 
 * it has too many directories already (max_dirs) or 
 * it has too few free inodes left (min_inodes) or 
 * it has too few free blocks left (min_blocks) or 
 * it's already running too large debt (max_debt). 
 * Parent's group is preferred, if it doesn't satisfy these 
 * conditions we search cyclically through the rest. If none 
 * of the groups look good we just look for a group with more 
 * free inodes than average (starting at parent's group). 
 * 
 * Debt is incremented each time we allocate a directory and decremented 
 * when we allocate an inode, within 0--255. 
 */ 

#define INODE_COST 64
#define BLOCK_COST 256

static int find_group_orlov(struct super_block *sb, struct inode *parent)
{
    int parent_group = EXT2_I(parent)->i_block_group;
    struct ext2_sb_info *sbi = EXT2_SB(sb);
    struct ext2_super_block *es = sbi->s_es;
    int ngroups = sbi->s_groups_count;
    int inodes_per_group = EXT2_INODES_PER_GROUP(sb);
    int freei;
    int avefreei;
    int free_blocks;
    int avefreeb;
    int blocks_per_dir;
    int ndirs;
    int max_debt, max_dirs, min_blocks, min_inodes;
    int group = -1, i;
    struct ext2_group_desc *desc;

    freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
    avefreei = freei / ngroups;
    free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
    avefreeb = free_blocks / ngroups;
    ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);

    if ((parent == sb->s_root->d_inode) ||
        (EXT2_I(parent)->i_flags & EXT2_TOPDIR_FL)) {
        struct ext2_group_desc *best_desc = NULL;
        int best_ndir = inodes_per_group;
        int best_group = -1;

        get_random_bytes(&group, sizeof(group));
        parent_group = (unsigned)group % ngroups;
        for (i = 0; i < ngroups; i++) {
            group = (parent_group + i) % ngroups;
            desc = ext2_get_group_desc (sb, group, NULL);
            if (!desc || !desc->bg_free_inodes_count)
                continue;
            if (le16_to_cpu(desc->bg_used_dirs_count) >= best_ndir)
                continue;
            if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
                continue;
            if (le16_to_cpu(desc->bg_free_blocks_count) < avefreeb)
                continue;
            best_group = group;
            best_ndir = le16_to_cpu(desc->bg_used_dirs_count);
            best_desc = desc;
        }
        if (best_group >= 0) {
            desc = best_desc;
            group = best_group;
            goto found;
        }
        goto fallback;
    }

    if (ndirs == 0)
        ndirs = 1;  /* percpu_counters are approximate... */

    blocks_per_dir = (le32_to_cpu(es->s_blocks_count)-free_blocks) / ndirs;

    max_dirs = ndirs / ngroups + inodes_per_group / 16;
    min_inodes = avefreei - inodes_per_group / 4;
    min_blocks = avefreeb - EXT2_BLOCKS_PER_GROUP(sb) / 4;

    max_debt = EXT2_BLOCKS_PER_GROUP(sb) / max(blocks_per_dir, BLOCK_COST);
    if (max_debt * INODE_COST > inodes_per_group)
        max_debt = inodes_per_group / INODE_COST;
    if (max_debt > 255)
        max_debt = 255;
    if (max_debt == 0)
        max_debt = 1;

    for (i = 0; i < ngroups; i++) {
        group = (parent_group + i) % ngroups;
        desc = ext2_get_group_desc (sb, group, NULL);
        if (!desc || !desc->bg_free_inodes_count)
            continue;
        if (sbi->s_debts[group] >= max_debt)
            continue;
        if (le16_to_cpu(desc->bg_used_dirs_count) >= max_dirs)
            continue;
        if (le16_to_cpu(desc->bg_free_inodes_count) < min_inodes)
            continue;
        if (le16_to_cpu(desc->bg_free_blocks_count) < min_blocks)
            continue;
        goto found;
    }

fallback:
    for (i = 0; i < ngroups; i++) {
        group = (parent_group + i) % ngroups;
        desc = ext2_get_group_desc (sb, group, NULL);
        if (!desc || !desc->bg_free_inodes_count)
            continue;
        if (le16_to_cpu(desc->bg_free_inodes_count) >= avefreei)
            goto found;
    }

    if (avefreei) {
        /*
         * The free-inodes counter is approximate, and for really small
         * filesystems the above test can fail to find any blockgroups
         */
        avefreei = 0;
        goto fallback;
    }

    return -1;

found:
    return group;
}

static int find_group_other(struct super_block *sb, struct inode *parent)
{
    int parent_group = EXT2_I(parent)->i_block_group;
    int ngroups = EXT2_SB(sb)->s_groups_count;
    struct ext2_group_desc *desc;
    int group, i;

    /*
     * Try to place the inode in its parent directory
     */
    group = parent_group;
    desc = ext2_get_group_desc (sb, group, NULL);
    if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&
            le16_to_cpu(desc->bg_free_blocks_count))
        goto found;

    /*
     * We're going to place this inode in a different blockgroup from its
     * parent.  We want to cause files in a common directory to all land in
     * the same blockgroup.  But we want files which are in a different
     * directory which shares a blockgroup with our parent to land in a
     * different blockgroup.
     *
     * So add our directory's i_ino into the starting point for the hash.
     */
    group = (group + parent->i_ino) % ngroups;

    /*
     * Use a quadratic hash to find a group with a free inode and some
     * free blocks.
     */
    for (i = 1; i < ngroups; i <<= 1) {
        group += i;
        if (group >= ngroups)
            group -= ngroups;
        desc = ext2_get_group_desc (sb, group, NULL);
        if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&
                le16_to_cpu(desc->bg_free_blocks_count))
            goto found;
    }

    /*
     * That failed: try linear search for a free inode, even if that group
     * has no free blocks.
     */
    group = parent_group;
    for (i = 0; i < ngroups; i++) {
        if (++group >= ngroups)
            group = 0;
        desc = ext2_get_group_desc (sb, group, NULL);
        if (desc && le16_to_cpu(desc->bg_free_inodes_count))
            goto found;
    }

    return -1;

found:
    return group;
}

struct inode *ext2_new_inode(struct inode *dir, umode_t mode,
                 const struct qstr *qstr)
{
    struct super_block *sb;
    struct buffer_head *bitmap_bh = NULL;
    struct buffer_head *bh2;
    int group, i;
    ino_t ino = 0;
    struct inode * inode;
    struct ext2_group_desc *gdp;
    struct ext2_super_block *es;
    struct ext2_inode_info *ei;
    struct ext2_sb_info *sbi;
    int err;

    sb = dir->i_sb;
    inode = new_inode(sb);
    if (!inode)
        return ERR_PTR(-ENOMEM);

    ei = EXT2_I(inode);
    sbi = EXT2_SB(sb);
    es = sbi->s_es;
    if (S_ISDIR(mode)) {
        if (test_opt(sb, OLDALLOC))
            group = find_group_dir(sb, dir);
        else
            group = find_group_orlov(sb, dir);
    } else 
        group = find_group_other(sb, dir);

    if (group == -1) {
        err = -ENOSPC;
        goto fail;
    }

    for (i = 0; i < sbi->s_groups_count; i++) {
        gdp = ext2_get_group_desc(sb, group, &bh2);
        brelse(bitmap_bh);
        bitmap_bh = read_inode_bitmap(sb, group);
        if (!bitmap_bh) {
            err = -EIO;
            goto fail;
        }
        ino = 0;

repeat_in_this_group:
        ino = ext2_find_next_zero_bit((unsigned long *)bitmap_bh->b_data,
                          EXT2_INODES_PER_GROUP(sb), ino);
        if (ino >= EXT2_INODES_PER_GROUP(sb)) {
            /*
             * Rare race: find_group_xx() decided that there were
             * free inodes in this group, but by the time we tried
             * to allocate one, they're all gone.  This can also
             * occur because the counters which find_group_orlov()
             * uses are approximate.  So just go and search the
             * next block group.
             */
            if (++group == sbi->s_groups_count)
                group = 0;
            continue;
        }
        if (ext2_set_bit_atomic(sb_bgl_lock(sbi, group),
                        ino, bitmap_bh->b_data)) {
            /* we lost this inode */
            if (++ino >= EXT2_INODES_PER_GROUP(sb)) {
                /* this group is exhausted, try next group */
                if (++group == sbi->s_groups_count)
                    group = 0;
                continue;
            }
            /* try to find free inode in the same group */
            goto repeat_in_this_group;
        }
        goto got;
    }

    /*
     * Scanned all blockgroups.
     */
    err = -ENOSPC;
    goto fail;
got:
    mark_buffer_dirty(bitmap_bh);
    if (sb->s_flags & MS_SYNCHRONOUS)
        sync_dirty_buffer(bitmap_bh);
    brelse(bitmap_bh);

    ino += group * EXT2_INODES_PER_GROUP(sb) + 1;
    if (ino < EXT2_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {
        ext2_error (sb, "ext2_new_inode",
                "reserved inode or inode > inodes count - "
                "block_group = %d,inode=%lu", group,
                (unsigned long) ino);
        err = -EIO;
        goto fail;
    }

    percpu_counter_add(&sbi->s_freeinodes_counter, -1);
    if (S_ISDIR(mode))
        percpu_counter_inc(&sbi->s_dirs_counter);

    spin_lock(sb_bgl_lock(sbi, group));
    le16_add_cpu(&gdp->bg_free_inodes_count, -1);
    if (S_ISDIR(mode)) {
        if (sbi->s_debts[group] < 255)
            sbi->s_debts[group]++;
        le16_add_cpu(&gdp->bg_used_dirs_count, 1);
    } else {
        if (sbi->s_debts[group])
            sbi->s_debts[group]--;
    }
    spin_unlock(sb_bgl_lock(sbi, group));

    mark_buffer_dirty(bh2);
    if (test_opt(sb, GRPID)) {
        inode->i_mode = mode;
        inode->i_uid = current_fsuid();
        inode->i_gid = dir->i_gid;
    } else
        inode_init_owner(inode, dir, mode);

    inode->i_ino = ino;
    inode->i_blocks = 0;
    inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
    memset(ei->i_data, 0, sizeof(ei->i_data));
    ei->i_flags =
        ext2_mask_flags(mode, EXT2_I(dir)->i_flags & EXT2_FL_INHERITED);
    ei->i_faddr = 0;
    ei->i_frag_no = 0;
    ei->i_frag_size = 0;
    ei->i_file_acl = 0;
    ei->i_dir_acl = 0;
    ei->i_dtime = 0;
    ei->i_block_alloc_info = NULL;
    ei->i_block_group = group;
    ei->i_dir_start_lookup = 0;
    ei->i_state = EXT2_STATE_NEW;
    ext2_set_inode_flags(inode);
    spin_lock(&sbi->s_next_gen_lock);
    inode->i_generation = sbi->s_next_generation++;
    spin_unlock(&sbi->s_next_gen_lock);
    if (insert_inode_locked(inode) < 0) {
        ext2_error(sb, "ext2_new_inode",
               "inode number already in use - inode=%lu",
               (unsigned long) ino);
        err = -EIO;
        goto fail;
    }

    dquot_initialize(inode);
    err = dquot_alloc_inode(inode);
    if (err)
        goto fail_drop;

    err = ext2_init_acl(inode, dir);
    if (err)
        goto fail_free_drop;

    err = ext2_init_security(inode, dir, qstr);
    if (err)
        goto fail_free_drop;

    mark_inode_dirty(inode);
    ext2_debug("allocating inode %lu\n", inode->i_ino);
    ext2_preread_inode(inode);
    return inode;

fail_free_drop:
    dquot_free_inode(inode);

fail_drop:
    dquot_drop(inode);
    inode->i_flags |= S_NOQUOTA;
    clear_nlink(inode);
    unlock_new_inode(inode);
    iput(inode);
    return ERR_PTR(err);

fail:
    make_bad_inode(inode);
    iput(inode);
    return ERR_PTR(err);
}

unsigned long ext2_count_free_inodes (struct super_block * sb)
{
    struct ext2_group_desc *desc;
    unsigned long desc_count = 0;
    int i;  

#ifdef EXT2FS_DEBUG
    struct ext2_super_block *es;
    unsigned long bitmap_count = 0;
    struct buffer_head *bitmap_bh = NULL;

    es = EXT2_SB(sb)->s_es;
    for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
        unsigned x;

        desc = ext2_get_group_desc (sb, i, NULL);
        if (!desc)
            continue;
        desc_count += le16_to_cpu(desc->bg_free_inodes_count);
        brelse(bitmap_bh);
        bitmap_bh = read_inode_bitmap(sb, i);
        if (!bitmap_bh)
            continue;

        x = ext2_count_free(bitmap_bh, EXT2_INODES_PER_GROUP(sb) / 8);
        printk("group %d: stored = %d, counted = %u\n",
            i, le16_to_cpu(desc->bg_free_inodes_count), x);
        bitmap_count += x;
    }
    brelse(bitmap_bh);
    printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
        (unsigned long)
        percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
        desc_count, bitmap_count);
    return desc_count;
#else
    for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
        desc = ext2_get_group_desc (sb, i, NULL);
        if (!desc)
            continue;
        desc_count += le16_to_cpu(desc->bg_free_inodes_count);
    }
    return desc_count;
#endif
}

/* Called at mount-time, super-block is locked */
unsigned long ext2_count_dirs (struct super_block * sb)
{
    unsigned long count = 0;
    int i;

    for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
        struct ext2_group_desc *gdp = ext2_get_group_desc (sb, i, NULL);
        if (!gdp)
            continue;
        count += le16_to_cpu(gdp->bg_used_dirs_count);
    }
    return count;
}