resize.c

Go to the documentation of this file.

/*
 *  linux/fs/ext3/resize.c
 *
 * Support for resizing an ext3 filesystem while it is mounted.
 *
 * Copyright (C) 2001, 2002 Andreas Dilger <[email protected]>
 *
 * This could probably be made into a module, because it is not often in use.
 */


#define EXT3FS_DEBUG

#include "ext3.h"


#define outside(b, first, last) ((b) < (first) || (b) >= (last))
#define inside(b, first, last)  ((b) >= (first) && (b) < (last))

static int verify_group_input(struct super_block *sb,
                  struct ext3_new_group_data *input)
{
    struct ext3_sb_info *sbi = EXT3_SB(sb);
    struct ext3_super_block *es = sbi->s_es;
    ext3_fsblk_t start = le32_to_cpu(es->s_blocks_count);
    ext3_fsblk_t end = start + input->blocks_count;
    unsigned group = input->group;
    ext3_fsblk_t itend = input->inode_table + sbi->s_itb_per_group;
    unsigned overhead = ext3_bg_has_super(sb, group) ?
        (1 + ext3_bg_num_gdb(sb, group) +
         le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;
    ext3_fsblk_t metaend = start + overhead;
    struct buffer_head *bh = NULL;
    ext3_grpblk_t free_blocks_count;
    int err = -EINVAL;

    input->free_blocks_count = free_blocks_count =
        input->blocks_count - 2 - overhead - sbi->s_itb_per_group;

    if (test_opt(sb, DEBUG))
        printk(KERN_DEBUG "EXT3-fs: adding %s group %u: %u blocks "
               "(%d free, %u reserved)\n",
               ext3_bg_has_super(sb, input->group) ? "normal" :
               "no-super", input->group, input->blocks_count,
               free_blocks_count, input->reserved_blocks);

    if (group != sbi->s_groups_count)
        ext3_warning(sb, __func__,
                 "Cannot add at group %u (only %lu groups)",
                 input->group, sbi->s_groups_count);
    else if ((start - le32_to_cpu(es->s_first_data_block)) %
         EXT3_BLOCKS_PER_GROUP(sb))
        ext3_warning(sb, __func__, "Last group not full");
    else if (input->reserved_blocks > input->blocks_count / 5)
        ext3_warning(sb, __func__, "Reserved blocks too high (%u)",
                 input->reserved_blocks);
    else if (free_blocks_count < 0)
        ext3_warning(sb, __func__, "Bad blocks count %u",
                 input->blocks_count);
    else if (!(bh = sb_bread(sb, end - 1)))
        ext3_warning(sb, __func__,
                 "Cannot read last block ("E3FSBLK")",
                 end - 1);
    else if (outside(input->block_bitmap, start, end))
        ext3_warning(sb, __func__,
                 "Block bitmap not in group (block %u)",
                 input->block_bitmap);
    else if (outside(input->inode_bitmap, start, end))
        ext3_warning(sb, __func__,
                 "Inode bitmap not in group (block %u)",
                 input->inode_bitmap);
    else if (outside(input->inode_table, start, end) ||
             outside(itend - 1, start, end))
        ext3_warning(sb, __func__,
                 "Inode table not in group (blocks %u-"E3FSBLK")",
                 input->inode_table, itend - 1);
    else if (input->inode_bitmap == input->block_bitmap)
        ext3_warning(sb, __func__,
                 "Block bitmap same as inode bitmap (%u)",
                 input->block_bitmap);
    else if (inside(input->block_bitmap, input->inode_table, itend))
        ext3_warning(sb, __func__,
                 "Block bitmap (%u) in inode table (%u-"E3FSBLK")",
                 input->block_bitmap, input->inode_table, itend-1);
    else if (inside(input->inode_bitmap, input->inode_table, itend))
        ext3_warning(sb, __func__,
                 "Inode bitmap (%u) in inode table (%u-"E3FSBLK")",
                 input->inode_bitmap, input->inode_table, itend-1);
    else if (inside(input->block_bitmap, start, metaend))
        ext3_warning(sb, __func__,
                 "Block bitmap (%u) in GDT table"
                 " ("E3FSBLK"-"E3FSBLK")",
                 input->block_bitmap, start, metaend - 1);
    else if (inside(input->inode_bitmap, start, metaend))
        ext3_warning(sb, __func__,
                 "Inode bitmap (%u) in GDT table"
                 " ("E3FSBLK"-"E3FSBLK")",
                 input->inode_bitmap, start, metaend - 1);
    else if (inside(input->inode_table, start, metaend) ||
             inside(itend - 1, start, metaend))
        ext3_warning(sb, __func__,
                 "Inode table (%u-"E3FSBLK") overlaps"
                 "GDT table ("E3FSBLK"-"E3FSBLK")",
                 input->inode_table, itend - 1, start, metaend - 1);
    else
        err = 0;
    brelse(bh);

    return err;
}

static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,
                  ext3_fsblk_t blk)
{
    struct buffer_head *bh;
    int err;

    bh = sb_getblk(sb, blk);
    if (!bh)
        return ERR_PTR(-EIO);
    if ((err = ext3_journal_get_write_access(handle, bh))) {
        brelse(bh);
        bh = ERR_PTR(err);
    } else {
        lock_buffer(bh);
        memset(bh->b_data, 0, sb->s_blocksize);
        set_buffer_uptodate(bh);
        unlock_buffer(bh);
    }

    return bh;
}

/*
 * To avoid calling the atomic setbit hundreds or thousands of times, we only
 * need to use it within a single byte (to ensure we get endianness right).
 * We can use memset for the rest of the bitmap as there are no other users.
 */
static void mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
{
    int i;

    if (start_bit >= end_bit)
        return;

    ext3_debug("mark end bits +%d through +%d used\n", start_bit, end_bit);
    for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
        ext3_set_bit(i, bitmap);
    if (i < end_bit)
        memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
}

/*
 * If we have fewer than thresh credits, extend by EXT3_MAX_TRANS_DATA.
 * If that fails, restart the transaction & regain write access for the
 * buffer head which is used for block_bitmap modifications.
 */
static int extend_or_restart_transaction(handle_t *handle, int thresh,
                     struct buffer_head *bh)
{
    int err;

    if (handle->h_buffer_credits >= thresh)
        return 0;

    err = ext3_journal_extend(handle, EXT3_MAX_TRANS_DATA);
    if (err < 0)
        return err;
    if (err) {
        err = ext3_journal_restart(handle, EXT3_MAX_TRANS_DATA);
        if (err)
            return err;
        err = ext3_journal_get_write_access(handle, bh);
        if (err)
            return err;
    }

    return 0;
}

/*
 * Set up the block and inode bitmaps, and the inode table for the new group.
 * This doesn't need to be part of the main transaction, since we are only
 * changing blocks outside the actual filesystem.  We still do journaling to
 * ensure the recovery is correct in case of a failure just after resize.
 * If any part of this fails, we simply abort the resize.
 */
static int setup_new_group_blocks(struct super_block *sb,
                  struct ext3_new_group_data *input)
{
    struct ext3_sb_info *sbi = EXT3_SB(sb);
    ext3_fsblk_t start = ext3_group_first_block_no(sb, input->group);
    int reserved_gdb = ext3_bg_has_super(sb, input->group) ?
        le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) : 0;
    unsigned long gdblocks = ext3_bg_num_gdb(sb, input->group);
    struct buffer_head *bh;
    handle_t *handle;
    ext3_fsblk_t block;
    ext3_grpblk_t bit;
    int i;
    int err = 0, err2;

    /* This transaction may be extended/restarted along the way */
    handle = ext3_journal_start_sb(sb, EXT3_MAX_TRANS_DATA);

    if (IS_ERR(handle))
        return PTR_ERR(handle);

    mutex_lock(&sbi->s_resize_lock);
    if (input->group != sbi->s_groups_count) {
        err = -EBUSY;
        goto exit_journal;
    }

    if (IS_ERR(bh = bclean(handle, sb, input->block_bitmap))) {
        err = PTR_ERR(bh);
        goto exit_journal;
    }

    if (ext3_bg_has_super(sb, input->group)) {
        ext3_debug("mark backup superblock %#04lx (+0)\n", start);
        ext3_set_bit(0, bh->b_data);
    }

    /* Copy all of the GDT blocks into the backup in this group */
    for (i = 0, bit = 1, block = start + 1;
         i < gdblocks; i++, block++, bit++) {
        struct buffer_head *gdb;

        ext3_debug("update backup group %#04lx (+%d)\n", block, bit);

        err = extend_or_restart_transaction(handle, 1, bh);
        if (err)
            goto exit_bh;

        gdb = sb_getblk(sb, block);
        if (!gdb) {
            err = -EIO;
            goto exit_bh;
        }
        if ((err = ext3_journal_get_write_access(handle, gdb))) {
            brelse(gdb);
            goto exit_bh;
        }
        lock_buffer(gdb);
        memcpy(gdb->b_data, sbi->s_group_desc[i]->b_data, gdb->b_size);
        set_buffer_uptodate(gdb);
        unlock_buffer(gdb);
        err = ext3_journal_dirty_metadata(handle, gdb);
        if (err) {
            brelse(gdb);
            goto exit_bh;
        }
        ext3_set_bit(bit, bh->b_data);
        brelse(gdb);
    }

    /* Zero out all of the reserved backup group descriptor table blocks */
    for (i = 0, bit = gdblocks + 1, block = start + bit;
         i < reserved_gdb; i++, block++, bit++) {
        struct buffer_head *gdb;

        ext3_debug("clear reserved block %#04lx (+%d)\n", block, bit);

        err = extend_or_restart_transaction(handle, 1, bh);
        if (err)
            goto exit_bh;

        if (IS_ERR(gdb = bclean(handle, sb, block))) {
            err = PTR_ERR(gdb);
            goto exit_bh;
        }
        err = ext3_journal_dirty_metadata(handle, gdb);
        if (err) {
            brelse(gdb);
            goto exit_bh;
        }
        ext3_set_bit(bit, bh->b_data);
        brelse(gdb);
    }
    ext3_debug("mark block bitmap %#04x (+%ld)\n", input->block_bitmap,
           input->block_bitmap - start);
    ext3_set_bit(input->block_bitmap - start, bh->b_data);
    ext3_debug("mark inode bitmap %#04x (+%ld)\n", input->inode_bitmap,
           input->inode_bitmap - start);
    ext3_set_bit(input->inode_bitmap - start, bh->b_data);

    /* Zero out all of the inode table blocks */
    for (i = 0, block = input->inode_table, bit = block - start;
         i < sbi->s_itb_per_group; i++, bit++, block++) {
        struct buffer_head *it;

        ext3_debug("clear inode block %#04lx (+%d)\n", block, bit);

        err = extend_or_restart_transaction(handle, 1, bh);
        if (err)
            goto exit_bh;

        if (IS_ERR(it = bclean(handle, sb, block))) {
            err = PTR_ERR(it);
            goto exit_bh;
        }
        err = ext3_journal_dirty_metadata(handle, it);
        if (err) {
            brelse(it);
            goto exit_bh;
        }
        brelse(it);
        ext3_set_bit(bit, bh->b_data);
    }

    err = extend_or_restart_transaction(handle, 2, bh);
    if (err)
        goto exit_bh;

    mark_bitmap_end(input->blocks_count, EXT3_BLOCKS_PER_GROUP(sb),
            bh->b_data);
    err = ext3_journal_dirty_metadata(handle, bh);
    if (err)
        goto exit_bh;
    brelse(bh);

    /* Mark unused entries in inode bitmap used */
    ext3_debug("clear inode bitmap %#04x (+%ld)\n",
           input->inode_bitmap, input->inode_bitmap - start);
    if (IS_ERR(bh = bclean(handle, sb, input->inode_bitmap))) {
        err = PTR_ERR(bh);
        goto exit_journal;
    }

    mark_bitmap_end(EXT3_INODES_PER_GROUP(sb), EXT3_BLOCKS_PER_GROUP(sb),
            bh->b_data);
    err = ext3_journal_dirty_metadata(handle, bh);
exit_bh:
    brelse(bh);

exit_journal:
    mutex_unlock(&sbi->s_resize_lock);
    if ((err2 = ext3_journal_stop(handle)) && !err)
        err = err2;

    return err;
}

/*
 * Iterate through the groups which hold BACKUP superblock/GDT copies in an
 * ext3 filesystem.  The counters should be initialized to 1, 5, and 7 before
 * calling this for the first time.  In a sparse filesystem it will be the
 * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
 * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
 */
static unsigned ext3_list_backups(struct super_block *sb, unsigned *three,
                  unsigned *five, unsigned *seven)
{
    unsigned *min = three;
    int mult = 3;
    unsigned ret;

    if (!EXT3_HAS_RO_COMPAT_FEATURE(sb,
                    EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
        ret = *min;
        *min += 1;
        return ret;
    }

    if (*five < *min) {
        min = five;
        mult = 5;
    }
    if (*seven < *min) {
        min = seven;
        mult = 7;
    }

    ret = *min;
    *min *= mult;

    return ret;
}

/*
 * Check that all of the backup GDT blocks are held in the primary GDT block.
 * It is assumed that they are stored in group order.  Returns the number of
 * groups in current filesystem that have BACKUPS, or -ve error code.
 */
static int verify_reserved_gdb(struct super_block *sb,
                   struct buffer_head *primary)
{
    const ext3_fsblk_t blk = primary->b_blocknr;
    const unsigned long end = EXT3_SB(sb)->s_groups_count;
    unsigned three = 1;
    unsigned five = 5;
    unsigned seven = 7;
    unsigned grp;
    __le32 *p = (__le32 *)primary->b_data;
    int gdbackups = 0;

    while ((grp = ext3_list_backups(sb, &three, &five, &seven)) < end) {
        if (le32_to_cpu(*p++) != grp * EXT3_BLOCKS_PER_GROUP(sb) + blk){
            ext3_warning(sb, __func__,
                     "reserved GDT "E3FSBLK
                     " missing grp %d ("E3FSBLK")",
                     blk, grp,
                     grp * EXT3_BLOCKS_PER_GROUP(sb) + blk);
            return -EINVAL;
        }
        if (++gdbackups > EXT3_ADDR_PER_BLOCK(sb))
            return -EFBIG;
    }

    return gdbackups;
}

/*
 * Called when we need to bring a reserved group descriptor table block into
 * use from the resize inode.  The primary copy of the new GDT block currently
 * is an indirect block (under the double indirect block in the resize inode).
 * The new backup GDT blocks will be stored as leaf blocks in this indirect
 * block, in group order.  Even though we know all the block numbers we need,
 * we check to ensure that the resize inode has actually reserved these blocks.
 *
 * Don't need to update the block bitmaps because the blocks are still in use.
 *
 * We get all of the error cases out of the way, so that we are sure to not
 * fail once we start modifying the data on disk, because JBD has no rollback.
 */
static int add_new_gdb(handle_t *handle, struct inode *inode,
               struct ext3_new_group_data *input,
               struct buffer_head **primary)
{
    struct super_block *sb = inode->i_sb;
    struct ext3_super_block *es = EXT3_SB(sb)->s_es;
    unsigned long gdb_num = input->group / EXT3_DESC_PER_BLOCK(sb);
    ext3_fsblk_t gdblock = EXT3_SB(sb)->s_sbh->b_blocknr + 1 + gdb_num;
    struct buffer_head **o_group_desc, **n_group_desc;
    struct buffer_head *dind;
    int gdbackups;
    struct ext3_iloc iloc;
    __le32 *data;
    int err;

    if (test_opt(sb, DEBUG))
        printk(KERN_DEBUG
               "EXT3-fs: ext3_add_new_gdb: adding group block %lu\n",
               gdb_num);

    /*
     * If we are not using the primary superblock/GDT copy don't resize,
     * because the user tools have no way of handling this.  Probably a
     * bad time to do it anyways.
     */
    if (EXT3_SB(sb)->s_sbh->b_blocknr !=
        le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block)) {
        ext3_warning(sb, __func__,
            "won't resize using backup superblock at %llu",
            (unsigned long long)EXT3_SB(sb)->s_sbh->b_blocknr);
        return -EPERM;
    }

    *primary = sb_bread(sb, gdblock);
    if (!*primary)
        return -EIO;

    if ((gdbackups = verify_reserved_gdb(sb, *primary)) < 0) {
        err = gdbackups;
        goto exit_bh;
    }

    data = EXT3_I(inode)->i_data + EXT3_DIND_BLOCK;
    dind = sb_bread(sb, le32_to_cpu(*data));
    if (!dind) {
        err = -EIO;
        goto exit_bh;
    }

    data = (__le32 *)dind->b_data;
    if (le32_to_cpu(data[gdb_num % EXT3_ADDR_PER_BLOCK(sb)]) != gdblock) {
        ext3_warning(sb, __func__,
                 "new group %u GDT block "E3FSBLK" not reserved",
                 input->group, gdblock);
        err = -EINVAL;
        goto exit_dind;
    }

    if ((err = ext3_journal_get_write_access(handle, EXT3_SB(sb)->s_sbh)))
        goto exit_dind;

    if ((err = ext3_journal_get_write_access(handle, *primary)))
        goto exit_sbh;

    if ((err = ext3_journal_get_write_access(handle, dind)))
        goto exit_primary;

    /* ext3_reserve_inode_write() gets a reference on the iloc */
    if ((err = ext3_reserve_inode_write(handle, inode, &iloc)))
        goto exit_dindj;

    n_group_desc = kmalloc((gdb_num + 1) * sizeof(struct buffer_head *),
            GFP_NOFS);
    if (!n_group_desc) {
        err = -ENOMEM;
        ext3_warning (sb, __func__,
                  "not enough memory for %lu groups", gdb_num + 1);
        goto exit_inode;
    }

    /*
     * Finally, we have all of the possible failures behind us...
     *
     * Remove new GDT block from inode double-indirect block and clear out
     * the new GDT block for use (which also "frees" the backup GDT blocks
     * from the reserved inode).  We don't need to change the bitmaps for
     * these blocks, because they are marked as in-use from being in the
     * reserved inode, and will become GDT blocks (primary and backup).
     */
    data[gdb_num % EXT3_ADDR_PER_BLOCK(sb)] = 0;
    err = ext3_journal_dirty_metadata(handle, dind);
    if (err)
        goto exit_group_desc;
    brelse(dind);
    dind = NULL;
    inode->i_blocks -= (gdbackups + 1) * sb->s_blocksize >> 9;
    err = ext3_mark_iloc_dirty(handle, inode, &iloc);
    if (err)
        goto exit_group_desc;
    memset((*primary)->b_data, 0, sb->s_blocksize);
    err = ext3_journal_dirty_metadata(handle, *primary);
    if (err)
        goto exit_group_desc;

    o_group_desc = EXT3_SB(sb)->s_group_desc;
    memcpy(n_group_desc, o_group_desc,
           EXT3_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
    n_group_desc[gdb_num] = *primary;
    EXT3_SB(sb)->s_group_desc = n_group_desc;
    EXT3_SB(sb)->s_gdb_count++;
    kfree(o_group_desc);

    le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
    err = ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);
    if (err)
        goto exit_inode;

    return 0;

exit_group_desc:
    kfree(n_group_desc);
exit_inode:
    //ext3_journal_release_buffer(handle, iloc.bh);
    brelse(iloc.bh);
exit_dindj:
    //ext3_journal_release_buffer(handle, dind);
exit_primary:
    //ext3_journal_release_buffer(handle, *primary);
exit_sbh:
    //ext3_journal_release_buffer(handle, *primary);
exit_dind:
    brelse(dind);
exit_bh:
    brelse(*primary);

    ext3_debug("leaving with error %d\n", err);
    return err;
}

/*
 * Called when we are adding a new group which has a backup copy of each of
 * the GDT blocks (i.e. sparse group) and there are reserved GDT blocks.
 * We need to add these reserved backup GDT blocks to the resize inode, so
 * that they are kept for future resizing and not allocated to files.
 *
 * Each reserved backup GDT block will go into a different indirect block.
 * The indirect blocks are actually the primary reserved GDT blocks,
 * so we know in advance what their block numbers are.  We only get the
 * double-indirect block to verify it is pointing to the primary reserved
 * GDT blocks so we don't overwrite a data block by accident.  The reserved
 * backup GDT blocks are stored in their reserved primary GDT block.
 */
static int reserve_backup_gdb(handle_t *handle, struct inode *inode,
                  struct ext3_new_group_data *input)
{
    struct super_block *sb = inode->i_sb;
    int reserved_gdb =le16_to_cpu(EXT3_SB(sb)->s_es->s_reserved_gdt_blocks);
    struct buffer_head **primary;
    struct buffer_head *dind;
    struct ext3_iloc iloc;
    ext3_fsblk_t blk;
    __le32 *data, *end;
    int gdbackups = 0;
    int res, i;
    int err;

    primary = kmalloc(reserved_gdb * sizeof(*primary), GFP_NOFS);
    if (!primary)
        return -ENOMEM;

    data = EXT3_I(inode)->i_data + EXT3_DIND_BLOCK;
    dind = sb_bread(sb, le32_to_cpu(*data));
    if (!dind) {
        err = -EIO;
        goto exit_free;
    }

    blk = EXT3_SB(sb)->s_sbh->b_blocknr + 1 + EXT3_SB(sb)->s_gdb_count;
    data = (__le32 *)dind->b_data + (EXT3_SB(sb)->s_gdb_count %
                     EXT3_ADDR_PER_BLOCK(sb));
    end = (__le32 *)dind->b_data + EXT3_ADDR_PER_BLOCK(sb);

    /* Get each reserved primary GDT block and verify it holds backups */
    for (res = 0; res < reserved_gdb; res++, blk++) {
        if (le32_to_cpu(*data) != blk) {
            ext3_warning(sb, __func__,
                     "reserved block "E3FSBLK
                     " not at offset %ld",
                     blk,
                     (long)(data - (__le32 *)dind->b_data));
            err = -EINVAL;
            goto exit_bh;
        }
        primary[res] = sb_bread(sb, blk);
        if (!primary[res]) {
            err = -EIO;
            goto exit_bh;
        }
        if ((gdbackups = verify_reserved_gdb(sb, primary[res])) < 0) {
            brelse(primary[res]);
            err = gdbackups;
            goto exit_bh;
        }
        if (++data >= end)
            data = (__le32 *)dind->b_data;
    }

    for (i = 0; i < reserved_gdb; i++) {
        if ((err = ext3_journal_get_write_access(handle, primary[i]))) {
            /*
            int j;
            for (j = 0; j < i; j++)
                ext3_journal_release_buffer(handle, primary[j]);
             */
            goto exit_bh;
        }
    }

    if ((err = ext3_reserve_inode_write(handle, inode, &iloc)))
        goto exit_bh;

    /*
     * Finally we can add each of the reserved backup GDT blocks from
     * the new group to its reserved primary GDT block.
     */
    blk = input->group * EXT3_BLOCKS_PER_GROUP(sb);
    for (i = 0; i < reserved_gdb; i++) {
        int err2;
        data = (__le32 *)primary[i]->b_data;
        /* printk("reserving backup %lu[%u] = %lu\n",
               primary[i]->b_blocknr, gdbackups,
               blk + primary[i]->b_blocknr); */
        data[gdbackups] = cpu_to_le32(blk + primary[i]->b_blocknr);
        err2 = ext3_journal_dirty_metadata(handle, primary[i]);
        if (!err)
            err = err2;
    }
    inode->i_blocks += reserved_gdb * sb->s_blocksize >> 9;
    ext3_mark_iloc_dirty(handle, inode, &iloc);

exit_bh:
    while (--res >= 0)
        brelse(primary[res]);
    brelse(dind);

exit_free:
    kfree(primary);

    return err;
}

/*
 * Update the backup copies of the ext3 metadata.  These don't need to be part
 * of the main resize transaction, because e2fsck will re-write them if there
 * is a problem (basically only OOM will cause a problem).  However, we
 * _should_ update the backups if possible, in case the primary gets trashed
 * for some reason and we need to run e2fsck from a backup superblock.  The
 * important part is that the new block and inode counts are in the backup
 * superblocks, and the location of the new group metadata in the GDT backups.
 *
 * We do not need take the s_resize_lock for this, because these
 * blocks are not otherwise touched by the filesystem code when it is
 * mounted.  We don't need to worry about last changing from
 * sbi->s_groups_count, because the worst that can happen is that we
 * do not copy the full number of backups at this time.  The resize
 * which changed s_groups_count will backup again.
 */
static void update_backups(struct super_block *sb,
               int blk_off, char *data, int size)
{
    struct ext3_sb_info *sbi = EXT3_SB(sb);
    const unsigned long last = sbi->s_groups_count;
    const int bpg = EXT3_BLOCKS_PER_GROUP(sb);
    unsigned three = 1;
    unsigned five = 5;
    unsigned seven = 7;
    unsigned group;
    int rest = sb->s_blocksize - size;
    handle_t *handle;
    int err = 0, err2;

    handle = ext3_journal_start_sb(sb, EXT3_MAX_TRANS_DATA);
    if (IS_ERR(handle)) {
        group = 1;
        err = PTR_ERR(handle);
        goto exit_err;
    }

    while ((group = ext3_list_backups(sb, &three, &five, &seven)) < last) {
        struct buffer_head *bh;

        /* Out of journal space, and can't get more - abort - so sad */
        if (handle->h_buffer_credits == 0 &&
            ext3_journal_extend(handle, EXT3_MAX_TRANS_DATA) &&
            (err = ext3_journal_restart(handle, EXT3_MAX_TRANS_DATA)))
            break;

        bh = sb_getblk(sb, group * bpg + blk_off);
        if (!bh) {
            err = -EIO;
            break;
        }
        ext3_debug("update metadata backup %#04lx\n",
              (unsigned long)bh->b_blocknr);
        if ((err = ext3_journal_get_write_access(handle, bh))) {
            brelse(bh);
            break;
        }
        lock_buffer(bh);
        memcpy(bh->b_data, data, size);
        if (rest)
            memset(bh->b_data + size, 0, rest);
        set_buffer_uptodate(bh);
        unlock_buffer(bh);
        err = ext3_journal_dirty_metadata(handle, bh);
        brelse(bh);
        if (err)
            break;
    }
    if ((err2 = ext3_journal_stop(handle)) && !err)
        err = err2;

    /*
     * Ugh! Need to have e2fsck write the backup copies.  It is too
     * late to revert the resize, we shouldn't fail just because of
     * the backup copies (they are only needed in case of corruption).
     *
     * However, if we got here we have a journal problem too, so we
     * can't really start a transaction to mark the superblock.
     * Chicken out and just set the flag on the hope it will be written
     * to disk, and if not - we will simply wait until next fsck.
     */
exit_err:
    if (err) {
        ext3_warning(sb, __func__,
                 "can't update backup for group %d (err %d), "
                 "forcing fsck on next reboot", group, err);
        sbi->s_mount_state &= ~EXT3_VALID_FS;
        sbi->s_es->s_state &= cpu_to_le16(~EXT3_VALID_FS);
        mark_buffer_dirty(sbi->s_sbh);
    }
}

/* Add group descriptor data to an existing or new group descriptor block.
 * Ensure we handle all possible error conditions _before_ we start modifying
 * the filesystem, because we cannot abort the transaction and not have it
 * write the data to disk.
 *
 * If we are on a GDT block boundary, we need to get the reserved GDT block.
 * Otherwise, we may need to add backup GDT blocks for a sparse group.
 *
 * We only need to hold the superblock lock while we are actually adding
 * in the new group's counts to the superblock.  Prior to that we have
 * not really "added" the group at all.  We re-check that we are still
 * adding in the last group in case things have changed since verifying.
 */
int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input)
{
    struct ext3_sb_info *sbi = EXT3_SB(sb);
    struct ext3_super_block *es = sbi->s_es;
    int reserved_gdb = ext3_bg_has_super(sb, input->group) ?
        le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
    struct buffer_head *primary = NULL;
    struct ext3_group_desc *gdp;
    struct inode *inode = NULL;
    handle_t *handle;
    int gdb_off, gdb_num;
    int err, err2;

    gdb_num = input->group / EXT3_DESC_PER_BLOCK(sb);
    gdb_off = input->group % EXT3_DESC_PER_BLOCK(sb);

    if (gdb_off == 0 && !EXT3_HAS_RO_COMPAT_FEATURE(sb,
                    EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
        ext3_warning(sb, __func__,
                 "Can't resize non-sparse filesystem further");
        return -EPERM;
    }

    if (le32_to_cpu(es->s_blocks_count) + input->blocks_count <
        le32_to_cpu(es->s_blocks_count)) {
        ext3_warning(sb, __func__, "blocks_count overflow\n");
        return -EINVAL;
    }

    if (le32_to_cpu(es->s_inodes_count) + EXT3_INODES_PER_GROUP(sb) <
        le32_to_cpu(es->s_inodes_count)) {
        ext3_warning(sb, __func__, "inodes_count overflow\n");
        return -EINVAL;
    }

    if (reserved_gdb || gdb_off == 0) {
        if (!EXT3_HAS_COMPAT_FEATURE(sb,
                         EXT3_FEATURE_COMPAT_RESIZE_INODE)
            || !le16_to_cpu(es->s_reserved_gdt_blocks)) {
            ext3_warning(sb, __func__,
                     "No reserved GDT blocks, can't resize");
            return -EPERM;
        }
        inode = ext3_iget(sb, EXT3_RESIZE_INO);
        if (IS_ERR(inode)) {
            ext3_warning(sb, __func__,
                     "Error opening resize inode");
            return PTR_ERR(inode);
        }
    }

    if ((err = verify_group_input(sb, input)))
        goto exit_put;

    if ((err = setup_new_group_blocks(sb, input)))
        goto exit_put;

    /*
     * We will always be modifying at least the superblock and a GDT
     * block.  If we are adding a group past the last current GDT block,
     * we will also modify the inode and the dindirect block.  If we
     * are adding a group with superblock/GDT backups  we will also
     * modify each of the reserved GDT dindirect blocks.
     */
    handle = ext3_journal_start_sb(sb,
                       ext3_bg_has_super(sb, input->group) ?
                       3 + reserved_gdb : 4);
    if (IS_ERR(handle)) {
        err = PTR_ERR(handle);
        goto exit_put;
    }

    mutex_lock(&sbi->s_resize_lock);
    if (input->group != sbi->s_groups_count) {
        ext3_warning(sb, __func__,
                 "multiple resizers run on filesystem!");
        err = -EBUSY;
        goto exit_journal;
    }

    if ((err = ext3_journal_get_write_access(handle, sbi->s_sbh)))
        goto exit_journal;

    /*
     * We will only either add reserved group blocks to a backup group
     * or remove reserved blocks for the first group in a new group block.
     * Doing both would be mean more complex code, and sane people don't
     * use non-sparse filesystems anymore.  This is already checked above.
     */
    if (gdb_off) {
        primary = sbi->s_group_desc[gdb_num];
        if ((err = ext3_journal_get_write_access(handle, primary)))
            goto exit_journal;

        if (reserved_gdb && ext3_bg_num_gdb(sb, input->group) &&
            (err = reserve_backup_gdb(handle, inode, input)))
            goto exit_journal;
    } else if ((err = add_new_gdb(handle, inode, input, &primary)))
        goto exit_journal;

    /*
     * OK, now we've set up the new group.  Time to make it active.
     *
     * We do not lock all allocations via s_resize_lock
     * so we have to be safe wrt. concurrent accesses the group
     * data.  So we need to be careful to set all of the relevant
     * group descriptor data etc. *before* we enable the group.
     *
     * The key field here is sbi->s_groups_count: as long as
     * that retains its old value, nobody is going to access the new
     * group.
     *
     * So first we update all the descriptor metadata for the new
     * group; then we update the total disk blocks count; then we
     * update the groups count to enable the group; then finally we
     * update the free space counts so that the system can start
     * using the new disk blocks.
     */

    /* Update group descriptor block for new group */
    gdp = (struct ext3_group_desc *)primary->b_data + gdb_off;

    gdp->bg_block_bitmap = cpu_to_le32(input->block_bitmap);
    gdp->bg_inode_bitmap = cpu_to_le32(input->inode_bitmap);
    gdp->bg_inode_table = cpu_to_le32(input->inode_table);
    gdp->bg_free_blocks_count = cpu_to_le16(input->free_blocks_count);
    gdp->bg_free_inodes_count = cpu_to_le16(EXT3_INODES_PER_GROUP(sb));

    /*
     * Make the new blocks and inodes valid next.  We do this before
     * increasing the group count so that once the group is enabled,
     * all of its blocks and inodes are already valid.
     *
     * We always allocate group-by-group, then block-by-block or
     * inode-by-inode within a group, so enabling these
     * blocks/inodes before the group is live won't actually let us
     * allocate the new space yet.
     */
    le32_add_cpu(&es->s_blocks_count, input->blocks_count);
    le32_add_cpu(&es->s_inodes_count, EXT3_INODES_PER_GROUP(sb));

    /*
     * We need to protect s_groups_count against other CPUs seeing
     * inconsistent state in the superblock.
     *
     * The precise rules we use are:
     *
     * * Writers of s_groups_count *must* hold s_resize_lock
     * AND
     * * Writers must perform a smp_wmb() after updating all dependent
     *   data and before modifying the groups count
     *
     * * Readers must hold s_resize_lock over the access
     * OR
     * * Readers must perform an smp_rmb() after reading the groups count
     *   and before reading any dependent data.
     *
     * NB. These rules can be relaxed when checking the group count
     * while freeing data, as we can only allocate from a block
     * group after serialising against the group count, and we can
     * only then free after serialising in turn against that
     * allocation.
     */
    smp_wmb();

    /* Update the global fs size fields */
    sbi->s_groups_count++;

    err = ext3_journal_dirty_metadata(handle, primary);
    if (err)
        goto exit_journal;

    /* Update the reserved block counts only once the new group is
     * active. */
    le32_add_cpu(&es->s_r_blocks_count, input->reserved_blocks);

    /* Update the free space counts */
    percpu_counter_add(&sbi->s_freeblocks_counter,
               input->free_blocks_count);
    percpu_counter_add(&sbi->s_freeinodes_counter,
               EXT3_INODES_PER_GROUP(sb));

    err = ext3_journal_dirty_metadata(handle, sbi->s_sbh);

exit_journal:
    mutex_unlock(&sbi->s_resize_lock);
    if ((err2 = ext3_journal_stop(handle)) && !err)
        err = err2;
    if (!err) {
        update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
                   sizeof(struct ext3_super_block));
        update_backups(sb, primary->b_blocknr, primary->b_data,
                   primary->b_size);
    }
exit_put:
    iput(inode);
    return err;
} /* ext3_group_add */

/* Extend the filesystem to the new number of blocks specified.  This entry
 * point is only used to extend the current filesystem to the end of the last
 * existing group.  It can be accessed via ioctl, or by "remount,resize=<size>"
 * for emergencies (because it has no dependencies on reserved blocks).
 *
 * If we _really_ wanted, we could use default values to call ext3_group_add()
 * allow the "remount" trick to work for arbitrary resizing, assuming enough
 * GDT blocks are reserved to grow to the desired size.
 */
int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es,
              ext3_fsblk_t n_blocks_count)
{
    ext3_fsblk_t o_blocks_count;
    ext3_grpblk_t last;
    ext3_grpblk_t add;
    struct buffer_head * bh;
    handle_t *handle;
    int err;
    unsigned long freed_blocks;

    /* We don't need to worry about locking wrt other resizers just
     * yet: we're going to revalidate es->s_blocks_count after
     * taking the s_resize_lock below. */
    o_blocks_count = le32_to_cpu(es->s_blocks_count);

    if (test_opt(sb, DEBUG))
        printk(KERN_DEBUG "EXT3-fs: extending last group from "E3FSBLK
               " up to "E3FSBLK" blocks\n",
               o_blocks_count, n_blocks_count);

    if (n_blocks_count == 0 || n_blocks_count == o_blocks_count)
        return 0;

    if (n_blocks_count > (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
        printk(KERN_ERR "EXT3-fs: filesystem on %s:"
            " too large to resize to "E3FSBLK" blocks safely\n",
            sb->s_id, n_blocks_count);
        if (sizeof(sector_t) < 8)
            ext3_warning(sb, __func__,
            "CONFIG_LBDAF not enabled\n");
        return -EINVAL;
    }

    if (n_blocks_count < o_blocks_count) {
        ext3_warning(sb, __func__,
                 "can't shrink FS - resize aborted");
        return -EBUSY;
    }

    /* Handle the remaining blocks in the last group only. */
    last = (o_blocks_count - le32_to_cpu(es->s_first_data_block)) %
        EXT3_BLOCKS_PER_GROUP(sb);

    if (last == 0) {
        ext3_warning(sb, __func__,
                 "need to use ext2online to resize further");
        return -EPERM;
    }

    add = EXT3_BLOCKS_PER_GROUP(sb) - last;

    if (o_blocks_count + add < o_blocks_count) {
        ext3_warning(sb, __func__, "blocks_count overflow");
        return -EINVAL;
    }

    if (o_blocks_count + add > n_blocks_count)
        add = n_blocks_count - o_blocks_count;

    if (o_blocks_count + add < n_blocks_count)
        ext3_warning(sb, __func__,
                 "will only finish group ("E3FSBLK
                 " blocks, %u new)",
                 o_blocks_count + add, add);

    /* See if the device is actually as big as what was requested */
    bh = sb_bread(sb, o_blocks_count + add -1);
    if (!bh) {
        ext3_warning(sb, __func__,
                 "can't read last block, resize aborted");
        return -ENOSPC;
    }
    brelse(bh);

    /* We will update the superblock, one block bitmap, and
     * one group descriptor via ext3_free_blocks().
     */
    handle = ext3_journal_start_sb(sb, 3);
    if (IS_ERR(handle)) {
        err = PTR_ERR(handle);
        ext3_warning(sb, __func__, "error %d on journal start",err);
        goto exit_put;
    }

    mutex_lock(&EXT3_SB(sb)->s_resize_lock);
    if (o_blocks_count != le32_to_cpu(es->s_blocks_count)) {
        ext3_warning(sb, __func__,
                 "multiple resizers run on filesystem!");
        mutex_unlock(&EXT3_SB(sb)->s_resize_lock);
        ext3_journal_stop(handle);
        err = -EBUSY;
        goto exit_put;
    }

    if ((err = ext3_journal_get_write_access(handle,
                         EXT3_SB(sb)->s_sbh))) {
        ext3_warning(sb, __func__,
                 "error %d on journal write access", err);
        mutex_unlock(&EXT3_SB(sb)->s_resize_lock);
        ext3_journal_stop(handle);
        goto exit_put;
    }
    es->s_blocks_count = cpu_to_le32(o_blocks_count + add);
    err = ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);
    mutex_unlock(&EXT3_SB(sb)->s_resize_lock);
    if (err) {
        ext3_warning(sb, __func__,
                 "error %d on journal dirty metadata", err);
        ext3_journal_stop(handle);
        goto exit_put;
    }
    ext3_debug("freeing blocks "E3FSBLK" through "E3FSBLK"\n",
           o_blocks_count, o_blocks_count + add);
    ext3_free_blocks_sb(handle, sb, o_blocks_count, add, &freed_blocks);
    ext3_debug("freed blocks "E3FSBLK" through "E3FSBLK"\n",
           o_blocks_count, o_blocks_count + add);
    if ((err = ext3_journal_stop(handle)))
        goto exit_put;
    if (test_opt(sb, DEBUG))
        printk(KERN_DEBUG "EXT3-fs: extended group to %u blocks\n",
               le32_to_cpu(es->s_blocks_count));
    update_backups(sb, EXT3_SB(sb)->s_sbh->b_blocknr, (char *)es,
               sizeof(struct ext3_super_block));
exit_put:
    return err;
} /* ext3_group_extend */