/*
 * Copyright IBM Corporation, 2007
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

#include <linux/slab.h>
#include "ext4_jbd2.h"

/*
 * The contiguous blocks details which can be
 * represented by a single extent
 */
struct migrate_struct {
        ext4_lblk_t first_block, last_block, curr_block;
        ext4_fsblk_t first_pblock, last_pblock;
};

static int finish_range(handle_t *handle, struct inode *inode,
                                struct migrate_struct *lb)

{
        int retval = 0, needed;
        struct ext4_extent newext;
        struct ext4_ext_path *path;
        if (lb->first_pblock == 0)
                return 0;

        /* Add the extent to temp inode*/
        newext.ee_block = cpu_to_le32(lb->first_block);
        newext.ee_len   = cpu_to_le16(lb->last_block - lb->first_block + 1);
        ext4_ext_store_pblock(&newext, lb->first_pblock);
        path = ext4_ext_find_extent(inode, lb->first_block, NULL);

        if (IS_ERR(path)) {
                retval = PTR_ERR(path);
                path = NULL;
                goto err_out;
        }

        /*
         * Calculate the credit needed to inserting this extent
         * Since we are doing this in loop we may accumalate extra
         * credit. But below we try to not accumalate too much
         * of them by restarting the journal.
         */
        needed = ext4_ext_calc_credits_for_single_extent(inode,
                    lb->last_block - lb->first_block + 1, path);

        /*
         * Make sure the credit we accumalated is not really high
         */
        if (needed && ext4_handle_has_enough_credits(handle,
                                                EXT4_RESERVE_TRANS_BLOCKS)) {
                retval = ext4_journal_restart(handle, needed);
                if (retval)
                        goto err_out;
        } else if (needed) {
                retval = ext4_journal_extend(handle, needed);
                if (retval) {
                        /*
                         * IF not able to extend the journal restart the journal
                         */
                        retval = ext4_journal_restart(handle, needed);
                        if (retval)
                                goto err_out;
                }
        }
        retval = ext4_ext_insert_extent(handle, inode, path, &newext, 0);
err_out:
        if (path) {
                ext4_ext_drop_refs(path);
                kfree(path);
        }
        lb->first_pblock = 0;
        return retval;
}

static int update_extent_range(handle_t *handle, struct inode *inode,
                               ext4_fsblk_t pblock, struct migrate_struct *lb)
{
        int retval;
        /*
         * See if we can add on to the existing range (if it exists)
         */
        if (lb->first_pblock &&
                (lb->last_pblock+1 == pblock) &&
                (lb->last_block+1 == lb->curr_block)) {
                lb->last_pblock = pblock;
                lb->last_block = lb->curr_block;
                lb->curr_block++;
                return 0;
        }
        /*
         * Start a new range.
         */
        retval = finish_range(handle, inode, lb);
        lb->first_pblock = lb->last_pblock = pblock;
        lb->first_block = lb->last_block = lb->curr_block;
        lb->curr_block++;
        return retval;
}

static int update_ind_extent_range(handle_t *handle, struct inode *inode,
                                   ext4_fsblk_t pblock,
                                   struct migrate_struct *lb)
{
        struct buffer_head *bh;
        __le32 *i_data;
        int i, retval = 0;
        unsigned long max_entries = inode->i_sb->s_blocksize >> 2;

        bh = sb_bread(inode->i_sb, pblock);
        if (!bh)
                return -EIO;

        i_data = (__le32 *)bh->b_data;
        for (i = 0; i < max_entries; i++) {
                if (i_data[i]) {
                        retval = update_extent_range(handle, inode,
                                                le32_to_cpu(i_data[i]), lb);
                        if (retval)
                                break;
                } else {
                        lb->curr_block++;
                }
        }
        put_bh(bh);
        return retval;

}

static int update_dind_extent_range(handle_t *handle, struct inode *inode,
                                    ext4_fsblk_t pblock,
                                    struct migrate_struct *lb)
{
        struct buffer_head *bh;
        __le32 *i_data;
        int i, retval = 0;
        unsigned long max_entries = inode->i_sb->s_blocksize >> 2;

        bh = sb_bread(inode->i_sb, pblock);
        if (!bh)
                return -EIO;

        i_data = (__le32 *)bh->b_data;
        for (i = 0; i < max_entries; i++) {
                if (i_data[i]) {
                        retval = update_ind_extent_range(handle, inode,
                                                le32_to_cpu(i_data[i]), lb);
                        if (retval)
                                break;
                } else {
                        /* Only update the file block number */
                        lb->curr_block += max_entries;
                }
        }
        put_bh(bh);
        return retval;

}

static int update_tind_extent_range(handle_t *handle, struct inode *inode,
                                    ext4_fsblk_t pblock,
                                    struct migrate_struct *lb)
{
        struct buffer_head *bh;
        __le32 *i_data;
        int i, retval = 0;
        unsigned long max_entries = inode->i_sb->s_blocksize >> 2;

        bh = sb_bread(inode->i_sb, pblock);
        if (!bh)
                return -EIO;

        i_data = (__le32 *)bh->b_data;
        for (i = 0; i < max_entries; i++) {
                if (i_data[i]) {
                        retval = update_dind_extent_range(handle, inode,
                                                le32_to_cpu(i_data[i]), lb);
                        if (retval)
                                break;
                } else {
                        /* Only update the file block number */
                        lb->curr_block += max_entries * max_entries;
                }
        }
        put_bh(bh);
        return retval;

}

static int extend_credit_for_blkdel(handle_t *handle, struct inode *inode)
{
        int retval = 0, needed;

        if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
                return 0;
        /*
         * We are freeing a blocks. During this we touch
         * superblock, group descriptor and block bitmap.
         * So allocate a credit of 3. We may update
         * quota (user and group).
         */
        needed = 3 + EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb);

        if (ext4_journal_extend(handle, needed) != 0)
                retval = ext4_journal_restart(handle, needed);

        return retval;
}

static int free_dind_blocks(handle_t *handle,
                                struct inode *inode, __le32 i_data)
{
        int i;
        __le32 *tmp_idata;
        struct buffer_head *bh;
        unsigned long max_entries = inode->i_sb->s_blocksize >> 2;

        bh = sb_bread(inode->i_sb, le32_to_cpu(i_data));
        if (!bh)
                return -EIO;

        tmp_idata = (__le32 *)bh->b_data;
        for (i = 0; i < max_entries; i++) {
                if (tmp_idata[i]) {
                        extend_credit_for_blkdel(handle, inode);
                        ext4_free_blocks(handle, inode, NULL,
                                         le32_to_cpu(tmp_idata[i]), 1,
                                         EXT4_FREE_BLOCKS_METADATA |
                                         EXT4_FREE_BLOCKS_FORGET);
                }
        }
        put_bh(bh);
        extend_credit_for_blkdel(handle, inode);
        ext4_free_blocks(handle, inode, NULL, le32_to_cpu(i_data), 1,
                         EXT4_FREE_BLOCKS_METADATA |
                         EXT4_FREE_BLOCKS_FORGET);
        return 0;
}

static int free_tind_blocks(handle_t *handle,
                                struct inode *inode, __le32 i_data)
{
        int i, retval = 0;
        __le32 *tmp_idata;
        struct buffer_head *bh;
        unsigned long max_entries = inode->i_sb->s_blocksize >> 2;

        bh = sb_bread(inode->i_sb, le32_to_cpu(i_data));
        if (!bh)
                return -EIO;

        tmp_idata = (__le32 *)bh->b_data;
        for (i = 0; i < max_entries; i++) {
                if (tmp_idata[i]) {
                        retval = free_dind_blocks(handle,
                                        inode, tmp_idata[i]);
                        if (retval) {
                                put_bh(bh);
                                return retval;
                        }
                }
        }
        put_bh(bh);
        extend_credit_for_blkdel(handle, inode);
        ext4_free_blocks(handle, inode, NULL, le32_to_cpu(i_data), 1,
                         EXT4_FREE_BLOCKS_METADATA |
                         EXT4_FREE_BLOCKS_FORGET);
        return 0;
}

static int free_ind_block(handle_t *handle, struct inode *inode, __le32 *i_data)
{
        int retval;

        /* ei->i_data[EXT4_IND_BLOCK] */
        if (i_data[0]) {
                extend_credit_for_blkdel(handle, inode);
                ext4_free_blocks(handle, inode, NULL,
                                le32_to_cpu(i_data[0]), 1,
                                 EXT4_FREE_BLOCKS_METADATA |
                                 EXT4_FREE_BLOCKS_FORGET);
        }

        /* ei->i_data[EXT4_DIND_BLOCK] */
        if (i_data[1]) {
                retval = free_dind_blocks(handle, inode, i_data[1]);
                if (retval)
                        return retval;
        }

        /* ei->i_data[EXT4_TIND_BLOCK] */
        if (i_data[2]) {
                retval = free_tind_blocks(handle, inode, i_data[2]);
                if (retval)
                        return retval;
        }
        return 0;
}

static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
                                                struct inode *tmp_inode)
{
        int retval;
        __le32  i_data[3];
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct ext4_inode_info *tmp_ei = EXT4_I(tmp_inode);

        /*
         * One credit accounted for writing the
         * i_data field of the original inode
         */
        retval = ext4_journal_extend(handle, 1);
        if (retval) {
                retval = ext4_journal_restart(handle, 1);
                if (retval)
                        goto err_out;
        }

        i_data[0] = ei->i_data[EXT4_IND_BLOCK];
        i_data[1] = ei->i_data[EXT4_DIND_BLOCK];
        i_data[2] = ei->i_data[EXT4_TIND_BLOCK];

        down_write(&EXT4_I(inode)->i_data_sem);
        /*
         * if EXT4_STATE_EXT_MIGRATE is cleared a block allocation
         * happened after we started the migrate. We need to
         * fail the migrate
         */
        if (!ext4_test_inode_state(inode, EXT4_STATE_EXT_MIGRATE)) {
                retval = -EAGAIN;
                up_write(&EXT4_I(inode)->i_data_sem);
                goto err_out;
        } else
                ext4_clear_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
        /*
         * We have the extent map build with the tmp inode.
         * Now copy the i_data across
         */
        ext4_set_inode_flag(inode, EXT4_INODE_EXTENTS);
        memcpy(ei->i_data, tmp_ei->i_data, sizeof(ei->i_data));

        /*
         * Update i_blocks with the new blocks that got
         * allocated while adding extents for extent index
         * blocks.
         *
         * While converting to extents we need not
         * update the orignal inode i_blocks for extent blocks
         * via quota APIs. The quota update happened via tmp_inode already.
         */
        spin_lock(&inode->i_lock);
        inode->i_blocks += tmp_inode->i_blocks;
        spin_unlock(&inode->i_lock);
        up_write(&EXT4_I(inode)->i_data_sem);

        /*
         * We mark the inode dirty after, because we decrement the
         * i_blocks when freeing the indirect meta-data blocks
         */
        retval = free_ind_block(handle, inode, i_data);
        ext4_mark_inode_dirty(handle, inode);

err_out:
        return retval;
}

static int free_ext_idx(handle_t *handle, struct inode *inode,
                                        struct ext4_extent_idx *ix)
{
        int i, retval = 0;
        ext4_fsblk_t block;
        struct buffer_head *bh;
        struct ext4_extent_header *eh;

        block = ext4_idx_pblock(ix);
        bh = sb_bread(inode->i_sb, block);
        if (!bh)
                return -EIO;

        eh = (struct ext4_extent_header *)bh->b_data;
        if (eh->eh_depth != 0) {
                ix = EXT_FIRST_INDEX(eh);
                for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ix++) {
                        retval = free_ext_idx(handle, inode, ix);
                        if (retval)
                                break;
                }
        }
        put_bh(bh);
        extend_credit_for_blkdel(handle, inode);
        ext4_free_blocks(handle, inode, NULL, block, 1,
                         EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
        return retval;
}

/*
 * Free the extent meta data blocks only
 */
static int free_ext_block(handle_t *handle, struct inode *inode)
{
        int i, retval = 0;
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct ext4_extent_header *eh = (struct ext4_extent_header *)ei->i_data;
        struct ext4_extent_idx *ix;
        if (eh->eh_depth == 0)
                /*
                 * No extra blocks allocated for extent meta data
                 */
                return 0;
        ix = EXT_FIRST_INDEX(eh);
        for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ix++) {
                retval = free_ext_idx(handle, inode, ix);
                if (retval)
                        return retval;
        }
        return retval;

}

int ext4_ext_migrate(struct inode *inode)
{
        handle_t *handle;
        int retval = 0, i;
        __le32 *i_data;
        struct ext4_inode_info *ei;
        struct inode *tmp_inode = NULL;
        struct migrate_struct lb;
        unsigned long max_entries;
        __u32 goal;
        uid_t owner[2];

        /*
         * If the filesystem does not support extents, or the inode
         * already is extent-based, error out.
         */
        if (!EXT4_HAS_INCOMPAT_FEATURE(inode->i_sb,
                                       EXT4_FEATURE_INCOMPAT_EXTENTS) ||
            (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
                return -EINVAL;

        if (S_ISLNK(inode->i_mode) && inode->i_blocks == 0)
                /*
                 * don't migrate fast symlink
                 */
                return retval;

        handle = ext4_journal_start(inode,
                                        EXT4_DATA_TRANS_BLOCKS(inode->i_sb) +
                                        EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                                        EXT4_MAXQUOTAS_INIT_BLOCKS(inode->i_sb)
                                        + 1);
        if (IS_ERR(handle)) {
                retval = PTR_ERR(handle);
                return retval;
        }
        goal = (((inode->i_ino - 1) / EXT4_INODES_PER_GROUP(inode->i_sb)) *
                EXT4_INODES_PER_GROUP(inode->i_sb)) + 1;
        owner[0] = i_uid_read(inode);
        owner[1] = i_gid_read(inode);
        tmp_inode = ext4_new_inode(handle, inode->i_sb->s_root->d_inode,
                                   S_IFREG, NULL, goal, owner);
        if (IS_ERR(tmp_inode)) {
                retval = PTR_ERR(tmp_inode);
                ext4_journal_stop(handle);
                return retval;
        }
        i_size_write(tmp_inode, i_size_read(inode));
        /*
         * Set the i_nlink to zero so it will be deleted later
         * when we drop inode reference.
         */
        clear_nlink(tmp_inode);

        ext4_ext_tree_init(handle, tmp_inode);
        ext4_orphan_add(handle, tmp_inode);
        ext4_journal_stop(handle);

        /*
         * start with one credit accounted for
         * superblock modification.
         *
         * For the tmp_inode we already have committed the
         * trascation that created the inode. Later as and
         * when we add extents we extent the journal
         */
        /*
         * Even though we take i_mutex we can still cause block
         * allocation via mmap write to holes. If we have allocated
         * new blocks we fail migrate.  New block allocation will
         * clear EXT4_STATE_EXT_MIGRATE flag.  The flag is updated
         * with i_data_sem held to prevent racing with block
         * allocation.
         */
        down_read((&EXT4_I(inode)->i_data_sem));
        ext4_set_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
        up_read((&EXT4_I(inode)->i_data_sem));

        handle = ext4_journal_start(inode, 1);
        if (IS_ERR(handle)) {
                /*
                 * It is impossible to update on-disk structures without
                 * a handle, so just rollback in-core changes and live other
                 * work to orphan_list_cleanup()
                 */
                ext4_orphan_del(NULL, tmp_inode);
                retval = PTR_ERR(handle);
                goto out;
        }

        ei = EXT4_I(inode);
        i_data = ei->i_data;
        memset(&lb, 0, sizeof(lb));

        /* 32 bit block address 4 bytes */
        max_entries = inode->i_sb->s_blocksize >> 2;
        for (i = 0; i < EXT4_NDIR_BLOCKS; i++) {
                if (i_data[i]) {
                        retval = update_extent_range(handle, tmp_inode,
                                                le32_to_cpu(i_data[i]), &lb);
                        if (retval)
                                goto err_out;
                } else
                        lb.curr_block++;
        }
        if (i_data[EXT4_IND_BLOCK]) {
                retval = update_ind_extent_range(handle, tmp_inode,
                                le32_to_cpu(i_data[EXT4_IND_BLOCK]), &lb);
                        if (retval)
                                goto err_out;
        } else
                lb.curr_block += max_entries;
        if (i_data[EXT4_DIND_BLOCK]) {
                retval = update_dind_extent_range(handle, tmp_inode,
                                le32_to_cpu(i_data[EXT4_DIND_BLOCK]), &lb);
                        if (retval)
                                goto err_out;
        } else
                lb.curr_block += max_entries * max_entries;
        if (i_data[EXT4_TIND_BLOCK]) {
                retval = update_tind_extent_range(handle, tmp_inode,
                                le32_to_cpu(i_data[EXT4_TIND_BLOCK]), &lb);
                        if (retval)
                                goto err_out;
        }
        /*
         * Build the last extent
         */
        retval = finish_range(handle, tmp_inode, &lb);
err_out:
        if (retval)
                /*
                 * Failure case delete the extent information with the
                 * tmp_inode
                 */
                free_ext_block(handle, tmp_inode);
        else {
                retval = ext4_ext_swap_inode_data(handle, inode, tmp_inode);
                if (retval)
                        /*
                         * if we fail to swap inode data free the extent
                         * details of the tmp inode
                         */
                        free_ext_block(handle, tmp_inode);
        }

        /* We mark the tmp_inode dirty via ext4_ext_tree_init. */
        if (ext4_journal_extend(handle, 1) != 0)
                ext4_journal_restart(handle, 1);

        /*
         * Mark the tmp_inode as of size zero
         */
        i_size_write(tmp_inode, 0);

        /*
         * set the  i_blocks count to zero
         * so that the ext4_delete_inode does the
         * right job
         *
         * We don't need to take the i_lock because
         * the inode is not visible to user space.
         */
        tmp_inode->i_blocks = 0;

        /* Reset the extent details */
        ext4_ext_tree_init(handle, tmp_inode);
        ext4_journal_stop(handle);
out:
        unlock_new_inode(tmp_inode);
        iput(tmp_inode);

        return retval;
}