move_extent.c

Go to the documentation of this file.

/*
 * Copyright (c) 2008,2009 NEC Software Tohoku, Ltd.
 * Written by Takashi Sato <[email protected]>
 *            Akira Fujita <[email protected]>
 *
 * 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 will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/fs.h>
#include <linux/quotaops.h>
#include <linux/slab.h>
#include "ext4_jbd2.h"
#include "ext4.h"

static inline int
get_ext_path(struct inode *inode, ext4_lblk_t lblock,
        struct ext4_ext_path **path)
{
    int ret = 0;

    *path = ext4_ext_find_extent(inode, lblock, *path);
    if (IS_ERR(*path)) {
        ret = PTR_ERR(*path);
        *path = NULL;
    } else if ((*path)[ext_depth(inode)].p_ext == NULL)
        ret = -ENODATA;

    return ret;
}

static void
copy_extent_status(struct ext4_extent *src, struct ext4_extent *dest)
{
    if (ext4_ext_is_uninitialized(src))
        ext4_ext_mark_uninitialized(dest);
    else
        dest->ee_len = cpu_to_le16(ext4_ext_get_actual_len(dest));
}

static int
mext_next_extent(struct inode *inode, struct ext4_ext_path *path,
              struct ext4_extent **extent)
{
    struct ext4_extent_header *eh;
    int ppos, leaf_ppos = path->p_depth;

    ppos = leaf_ppos;
    if (EXT_LAST_EXTENT(path[ppos].p_hdr) > path[ppos].p_ext) {
        /* leaf block */
        *extent = ++path[ppos].p_ext;
        path[ppos].p_block = ext4_ext_pblock(path[ppos].p_ext);
        return 0;
    }

    while (--ppos >= 0) {
        if (EXT_LAST_INDEX(path[ppos].p_hdr) >
            path[ppos].p_idx) {
            int cur_ppos = ppos;

            /* index block */
            path[ppos].p_idx++;
            path[ppos].p_block = ext4_idx_pblock(path[ppos].p_idx);
            if (path[ppos+1].p_bh)
                brelse(path[ppos+1].p_bh);
            path[ppos+1].p_bh =
                sb_bread(inode->i_sb, path[ppos].p_block);
            if (!path[ppos+1].p_bh)
                return -EIO;
            path[ppos+1].p_hdr =
                ext_block_hdr(path[ppos+1].p_bh);

            /* Halfway index block */
            while (++cur_ppos < leaf_ppos) {
                path[cur_ppos].p_idx =
                    EXT_FIRST_INDEX(path[cur_ppos].p_hdr);
                path[cur_ppos].p_block =
                    ext4_idx_pblock(path[cur_ppos].p_idx);
                if (path[cur_ppos+1].p_bh)
                    brelse(path[cur_ppos+1].p_bh);
                path[cur_ppos+1].p_bh = sb_bread(inode->i_sb,
                    path[cur_ppos].p_block);
                if (!path[cur_ppos+1].p_bh)
                    return -EIO;
                path[cur_ppos+1].p_hdr =
                    ext_block_hdr(path[cur_ppos+1].p_bh);
            }

            path[leaf_ppos].p_ext = *extent = NULL;

            eh = path[leaf_ppos].p_hdr;
            if (le16_to_cpu(eh->eh_entries) == 0)
                /* empty leaf is found */
                return -ENODATA;

            /* leaf block */
            path[leaf_ppos].p_ext = *extent =
                EXT_FIRST_EXTENT(path[leaf_ppos].p_hdr);
            path[leaf_ppos].p_block =
                    ext4_ext_pblock(path[leaf_ppos].p_ext);
            return 0;
        }
    }
    /* We found the last extent */
    return 1;
}

static void
double_down_write_data_sem(struct inode *first, struct inode *second)
{
    if (first < second) {
        down_write(&EXT4_I(first)->i_data_sem);
        down_write_nested(&EXT4_I(second)->i_data_sem, SINGLE_DEPTH_NESTING);
    } else {
        down_write(&EXT4_I(second)->i_data_sem);
        down_write_nested(&EXT4_I(first)->i_data_sem, SINGLE_DEPTH_NESTING);

    }
}

static void
double_up_write_data_sem(struct inode *orig_inode, struct inode *donor_inode)
{
    up_write(&EXT4_I(orig_inode)->i_data_sem);
    up_write(&EXT4_I(donor_inode)->i_data_sem);
}

static int
mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
        struct ext4_extent *o_start, struct ext4_extent *o_end,
        struct ext4_extent *start_ext, struct ext4_extent *new_ext,
        struct ext4_extent *end_ext)
{
    struct ext4_ext_path *orig_path = NULL;
    ext4_lblk_t eblock = 0;
    int new_flag = 0;
    int end_flag = 0;
    int err = 0;

    if (start_ext->ee_len && new_ext->ee_len && end_ext->ee_len) {
        if (o_start == o_end) {

            /*       start_ext   new_ext    end_ext
             * donor |---------|-----------|--------|
             * orig  |------------------------------|
             */
            end_flag = 1;
        } else {

            /*       start_ext   new_ext   end_ext
             * donor |---------|----------|---------|
             * orig  |---------------|--------------|
             */
            o_end->ee_block = end_ext->ee_block;
            o_end->ee_len = end_ext->ee_len;
            ext4_ext_store_pblock(o_end, ext4_ext_pblock(end_ext));
        }

        o_start->ee_len = start_ext->ee_len;
        eblock = le32_to_cpu(start_ext->ee_block);
        new_flag = 1;

    } else if (start_ext->ee_len && new_ext->ee_len &&
           !end_ext->ee_len && o_start == o_end) {

        /*   start_ext  new_ext
         * donor |--------------|---------------|
         * orig  |------------------------------|
         */
        o_start->ee_len = start_ext->ee_len;
        eblock = le32_to_cpu(start_ext->ee_block);
        new_flag = 1;

    } else if (!start_ext->ee_len && new_ext->ee_len &&
           end_ext->ee_len && o_start == o_end) {

        /*    new_ext   end_ext
         * donor |--------------|---------------|
         * orig  |------------------------------|
         */
        o_end->ee_block = end_ext->ee_block;
        o_end->ee_len = end_ext->ee_len;
        ext4_ext_store_pblock(o_end, ext4_ext_pblock(end_ext));

        /*
         * Set 0 to the extent block if new_ext was
         * the first block.
         */
        if (new_ext->ee_block)
            eblock = le32_to_cpu(new_ext->ee_block);

        new_flag = 1;
    } else {
        ext4_debug("ext4 move extent: Unexpected insert case\n");
        return -EIO;
    }

    if (new_flag) {
        err = get_ext_path(orig_inode, eblock, &orig_path);
        if (err)
            goto out;

        if (ext4_ext_insert_extent(handle, orig_inode,
                    orig_path, new_ext, 0))
            goto out;
    }

    if (end_flag) {
        err = get_ext_path(orig_inode,
                le32_to_cpu(end_ext->ee_block) - 1, &orig_path);
        if (err)
            goto out;

        if (ext4_ext_insert_extent(handle, orig_inode,
                       orig_path, end_ext, 0))
            goto out;
    }
out:
    if (orig_path) {
        ext4_ext_drop_refs(orig_path);
        kfree(orig_path);
    }

    return err;

}

static void
mext_insert_inside_block(struct ext4_extent *o_start,
                  struct ext4_extent *o_end,
                  struct ext4_extent *start_ext,
                  struct ext4_extent *new_ext,
                  struct ext4_extent *end_ext,
                  struct ext4_extent_header *eh,
                  int range_to_move)
{
    int i = 0;
    unsigned long len;

    /* Move the existing extents */
    if (range_to_move && o_end < EXT_LAST_EXTENT(eh)) {
        len = (unsigned long)(EXT_LAST_EXTENT(eh) + 1) -
            (unsigned long)(o_end + 1);
        memmove(o_end + 1 + range_to_move, o_end + 1, len);
    }

    /* Insert start entry */
    if (start_ext->ee_len)
        o_start[i++].ee_len = start_ext->ee_len;

    /* Insert new entry */
    if (new_ext->ee_len) {
        o_start[i] = *new_ext;
        ext4_ext_store_pblock(&o_start[i++], ext4_ext_pblock(new_ext));
    }

    /* Insert end entry */
    if (end_ext->ee_len)
        o_start[i] = *end_ext;

    /* Increment the total entries counter on the extent block */
    le16_add_cpu(&eh->eh_entries, range_to_move);
}

static int
mext_insert_extents(handle_t *handle, struct inode *orig_inode,
             struct ext4_ext_path *orig_path,
             struct ext4_extent *o_start,
             struct ext4_extent *o_end,
             struct ext4_extent *start_ext,
             struct ext4_extent *new_ext,
             struct ext4_extent *end_ext)
{
    struct  ext4_extent_header *eh;
    unsigned long need_slots, slots_range;
    int range_to_move, depth, ret;

    /*
     * The extents need to be inserted
     * start_extent + new_extent + end_extent.
     */
    need_slots = (start_ext->ee_len ? 1 : 0) + (end_ext->ee_len ? 1 : 0) +
        (new_ext->ee_len ? 1 : 0);

    /* The number of slots between start and end */
    slots_range = ((unsigned long)(o_end + 1) - (unsigned long)o_start + 1)
        / sizeof(struct ext4_extent);

    /* Range to move the end of extent */
    range_to_move = need_slots - slots_range;
    depth = orig_path->p_depth;
    orig_path += depth;
    eh = orig_path->p_hdr;

    if (depth) {
        /* Register to journal */
        ret = ext4_journal_get_write_access(handle, orig_path->p_bh);
        if (ret)
            return ret;
    }

    /* Expansion */
    if (range_to_move > 0 &&
        (range_to_move > le16_to_cpu(eh->eh_max)
            - le16_to_cpu(eh->eh_entries))) {

        ret = mext_insert_across_blocks(handle, orig_inode, o_start,
                    o_end, start_ext, new_ext, end_ext);
        if (ret < 0)
            return ret;
    } else
        mext_insert_inside_block(o_start, o_end, start_ext, new_ext,
                        end_ext, eh, range_to_move);

    if (depth) {
        ret = ext4_handle_dirty_metadata(handle, orig_inode,
                         orig_path->p_bh);
        if (ret)
            return ret;
    } else {
        ret = ext4_mark_inode_dirty(handle, orig_inode);
        if (ret < 0)
            return ret;
    }

    return 0;
}

static int
mext_leaf_block(handle_t *handle, struct inode *orig_inode,
             struct ext4_ext_path *orig_path, struct ext4_extent *dext,
             ext4_lblk_t *from)
{
    struct ext4_extent *oext, *o_start, *o_end, *prev_ext;
    struct ext4_extent new_ext, start_ext, end_ext;
    ext4_lblk_t new_ext_end;
    int oext_alen, new_ext_alen, end_ext_alen;
    int depth = ext_depth(orig_inode);
    int ret;

    start_ext.ee_block = end_ext.ee_block = 0;
    o_start = o_end = oext = orig_path[depth].p_ext;
    oext_alen = ext4_ext_get_actual_len(oext);
    start_ext.ee_len = end_ext.ee_len = 0;

    new_ext.ee_block = cpu_to_le32(*from);
    ext4_ext_store_pblock(&new_ext, ext4_ext_pblock(dext));
    new_ext.ee_len = dext->ee_len;
    new_ext_alen = ext4_ext_get_actual_len(&new_ext);
    new_ext_end = le32_to_cpu(new_ext.ee_block) + new_ext_alen - 1;

    /*
     * Case: original extent is first
     * oext      |--------|
     * new_ext      |--|
     * start_ext |--|
     */
    if (le32_to_cpu(oext->ee_block) < le32_to_cpu(new_ext.ee_block) &&
        le32_to_cpu(new_ext.ee_block) <
        le32_to_cpu(oext->ee_block) + oext_alen) {
        start_ext.ee_len = cpu_to_le16(le32_to_cpu(new_ext.ee_block) -
                           le32_to_cpu(oext->ee_block));
        start_ext.ee_block = oext->ee_block;
        copy_extent_status(oext, &start_ext);
    } else if (oext > EXT_FIRST_EXTENT(orig_path[depth].p_hdr)) {
        prev_ext = oext - 1;
        /*
         * We can merge new_ext into previous extent,
         * if these are contiguous and same extent type.
         */
        if (ext4_can_extents_be_merged(orig_inode, prev_ext,
                           &new_ext)) {
            o_start = prev_ext;
            start_ext.ee_len = cpu_to_le16(
                ext4_ext_get_actual_len(prev_ext) +
                new_ext_alen);
            start_ext.ee_block = oext->ee_block;
            copy_extent_status(prev_ext, &start_ext);
            new_ext.ee_len = 0;
        }
    }

    /*
     * Case: new_ext_end must be less than oext
     * oext      |-----------|
     * new_ext       |-------|
     */
    if (le32_to_cpu(oext->ee_block) + oext_alen - 1 < new_ext_end) {
        EXT4_ERROR_INODE(orig_inode,
            "new_ext_end(%u) should be less than or equal to "
            "oext->ee_block(%u) + oext_alen(%d) - 1",
            new_ext_end, le32_to_cpu(oext->ee_block),
            oext_alen);
        ret = -EIO;
        goto out;
    }

    /*
     * Case: new_ext is smaller than original extent
     * oext    |---------------|
     * new_ext |-----------|
     * end_ext             |---|
     */
    if (le32_to_cpu(oext->ee_block) <= new_ext_end &&
        new_ext_end < le32_to_cpu(oext->ee_block) + oext_alen - 1) {
        end_ext.ee_len =
            cpu_to_le16(le32_to_cpu(oext->ee_block) +
            oext_alen - 1 - new_ext_end);
        copy_extent_status(oext, &end_ext);
        end_ext_alen = ext4_ext_get_actual_len(&end_ext);
        ext4_ext_store_pblock(&end_ext,
            (ext4_ext_pblock(o_end) + oext_alen - end_ext_alen));
        end_ext.ee_block =
            cpu_to_le32(le32_to_cpu(o_end->ee_block) +
            oext_alen - end_ext_alen);
    }

    ret = mext_insert_extents(handle, orig_inode, orig_path, o_start,
                o_end, &start_ext, &new_ext, &end_ext);
out:
    return ret;
}

static int
mext_calc_swap_extents(struct ext4_extent *tmp_dext,
                  struct ext4_extent *tmp_oext,
                  ext4_lblk_t orig_off, ext4_lblk_t donor_off,
                  ext4_lblk_t max_count)
{
    ext4_lblk_t diff, orig_diff;
    struct ext4_extent dext_old, oext_old;

    BUG_ON(orig_off != donor_off);

    /* original and donor extents have to cover the same block offset */
    if (orig_off < le32_to_cpu(tmp_oext->ee_block) ||
        le32_to_cpu(tmp_oext->ee_block) +
            ext4_ext_get_actual_len(tmp_oext) - 1 < orig_off)
        return -ENODATA;

    if (orig_off < le32_to_cpu(tmp_dext->ee_block) ||
        le32_to_cpu(tmp_dext->ee_block) +
            ext4_ext_get_actual_len(tmp_dext) - 1 < orig_off)
        return -ENODATA;

    dext_old = *tmp_dext;
    oext_old = *tmp_oext;

    /* When tmp_dext is too large, pick up the target range. */
    diff = donor_off - le32_to_cpu(tmp_dext->ee_block);

    ext4_ext_store_pblock(tmp_dext, ext4_ext_pblock(tmp_dext) + diff);
    le32_add_cpu(&tmp_dext->ee_block, diff);
    le16_add_cpu(&tmp_dext->ee_len, -diff);

    if (max_count < ext4_ext_get_actual_len(tmp_dext))
        tmp_dext->ee_len = cpu_to_le16(max_count);

    orig_diff = orig_off - le32_to_cpu(tmp_oext->ee_block);
    ext4_ext_store_pblock(tmp_oext, ext4_ext_pblock(tmp_oext) + orig_diff);

    /* Adjust extent length if donor extent is larger than orig */
    if (ext4_ext_get_actual_len(tmp_dext) >
        ext4_ext_get_actual_len(tmp_oext) - orig_diff)
        tmp_dext->ee_len = cpu_to_le16(le16_to_cpu(tmp_oext->ee_len) -
                        orig_diff);

    tmp_oext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(tmp_dext));

    copy_extent_status(&oext_old, tmp_dext);
    copy_extent_status(&dext_old, tmp_oext);

    return 0;
}

static int
mext_check_coverage(struct inode *inode, ext4_lblk_t from, ext4_lblk_t count,
              int uninit, int *err)
{
    struct ext4_ext_path *path = NULL;
    struct ext4_extent *ext;
    ext4_lblk_t last = from + count;
    while (from < last) {
        *err = get_ext_path(inode, from, &path);
        if (*err)
            return 0;
        ext = path[ext_depth(inode)].p_ext;
        if (!ext) {
            ext4_ext_drop_refs(path);
            return 0;
        }
        if (uninit != ext4_ext_is_uninitialized(ext)) {
            ext4_ext_drop_refs(path);
            return 0;
        }
        from += ext4_ext_get_actual_len(ext);
        ext4_ext_drop_refs(path);
    }
    return 1;
}

static int
mext_replace_branches(handle_t *handle, struct inode *orig_inode,
               struct inode *donor_inode, ext4_lblk_t from,
               ext4_lblk_t count, int *err)
{
    struct ext4_ext_path *orig_path = NULL;
    struct ext4_ext_path *donor_path = NULL;
    struct ext4_extent *oext, *dext;
    struct ext4_extent tmp_dext, tmp_oext;
    ext4_lblk_t orig_off = from, donor_off = from;
    int depth;
    int replaced_count = 0;
    int dext_alen;

    /* Get the original extent for the block "orig_off" */
    *err = get_ext_path(orig_inode, orig_off, &orig_path);
    if (*err)
        goto out;

    /* Get the donor extent for the head */
    *err = get_ext_path(donor_inode, donor_off, &donor_path);
    if (*err)
        goto out;
    depth = ext_depth(orig_inode);
    oext = orig_path[depth].p_ext;
    tmp_oext = *oext;

    depth = ext_depth(donor_inode);
    dext = donor_path[depth].p_ext;
    tmp_dext = *dext;

    *err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
                      donor_off, count);
    if (*err)
        goto out;

    /* Loop for the donor extents */
    while (1) {
        /* The extent for donor must be found. */
        if (!dext) {
            EXT4_ERROR_INODE(donor_inode,
                   "The extent for donor must be found");
            *err = -EIO;
            goto out;
        } else if (donor_off != le32_to_cpu(tmp_dext.ee_block)) {
            EXT4_ERROR_INODE(donor_inode,
                "Donor offset(%u) and the first block of donor "
                "extent(%u) should be equal",
                donor_off,
                le32_to_cpu(tmp_dext.ee_block));
            *err = -EIO;
            goto out;
        }

        /* Set donor extent to orig extent */
        *err = mext_leaf_block(handle, orig_inode,
                       orig_path, &tmp_dext, &orig_off);
        if (*err)
            goto out;

        /* Set orig extent to donor extent */
        *err = mext_leaf_block(handle, donor_inode,
                       donor_path, &tmp_oext, &donor_off);
        if (*err)
            goto out;

        dext_alen = ext4_ext_get_actual_len(&tmp_dext);
        replaced_count += dext_alen;
        donor_off += dext_alen;
        orig_off += dext_alen;

        /* Already moved the expected blocks */
        if (replaced_count >= count)
            break;

        if (orig_path)
            ext4_ext_drop_refs(orig_path);
        *err = get_ext_path(orig_inode, orig_off, &orig_path);
        if (*err)
            goto out;
        depth = ext_depth(orig_inode);
        oext = orig_path[depth].p_ext;
        tmp_oext = *oext;

        if (donor_path)
            ext4_ext_drop_refs(donor_path);
        *err = get_ext_path(donor_inode, donor_off, &donor_path);
        if (*err)
            goto out;
        depth = ext_depth(donor_inode);
        dext = donor_path[depth].p_ext;
        tmp_dext = *dext;

        *err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
                       donor_off, count - replaced_count);
        if (*err)
            goto out;
    }

out:
    if (orig_path) {
        ext4_ext_drop_refs(orig_path);
        kfree(orig_path);
    }
    if (donor_path) {
        ext4_ext_drop_refs(donor_path);
        kfree(donor_path);
    }

    ext4_ext_invalidate_cache(orig_inode);
    ext4_ext_invalidate_cache(donor_inode);

    return replaced_count;
}

static int
mext_page_double_lock(struct inode *inode1, struct inode *inode2,
              pgoff_t index, struct page *page[2])
{
    struct address_space *mapping[2];
    unsigned fl = AOP_FLAG_NOFS;

    BUG_ON(!inode1 || !inode2);
    if (inode1 < inode2) {
        mapping[0] = inode1->i_mapping;
        mapping[1] = inode2->i_mapping;
    } else {
        mapping[0] = inode2->i_mapping;
        mapping[1] = inode1->i_mapping;
    }

    page[0] = grab_cache_page_write_begin(mapping[0], index, fl);
    if (!page[0])
        return -ENOMEM;

    page[1] = grab_cache_page_write_begin(mapping[1], index, fl);
    if (!page[1]) {
        unlock_page(page[0]);
        page_cache_release(page[0]);
        return -ENOMEM;
    }

    if (inode1 > inode2) {
        struct page *tmp;
        tmp = page[0];
        page[0] = page[1];
        page[1] = tmp;
    }
    return 0;
}

/* Force page buffers uptodate w/o dropping page's lock */
static int
mext_page_mkuptodate(struct page *page, unsigned from, unsigned to)
{
    struct inode *inode = page->mapping->host;
    sector_t block;
    struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
    unsigned int blocksize, block_start, block_end;
    int i, err,  nr = 0, partial = 0;
    BUG_ON(!PageLocked(page));
    BUG_ON(PageWriteback(page));

    if (PageUptodate(page))
        return 0;

    blocksize = 1 << inode->i_blkbits;
    if (!page_has_buffers(page))
        create_empty_buffers(page, blocksize, 0);

    head = page_buffers(page);
    block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
    for (bh = head, block_start = 0; bh != head || !block_start;
         block++, block_start = block_end, bh = bh->b_this_page) {
        block_end = block_start + blocksize;
        if (block_end <= from || block_start >= to) {
            if (!buffer_uptodate(bh))
                partial = 1;
            continue;
        }
        if (buffer_uptodate(bh))
            continue;
        if (!buffer_mapped(bh)) {
            int err = 0;
            err = ext4_get_block(inode, block, bh, 0);
            if (err) {
                SetPageError(page);
                return err;
            }
            if (!buffer_mapped(bh)) {
                zero_user(page, block_start, blocksize);
                if (!err)
                    set_buffer_uptodate(bh);
                continue;
            }
        }
        BUG_ON(nr >= MAX_BUF_PER_PAGE);
        arr[nr++] = bh;
    }
    /* No io required */
    if (!nr)
        goto out;

    for (i = 0; i < nr; i++) {
        bh = arr[i];
        if (!bh_uptodate_or_lock(bh)) {
            err = bh_submit_read(bh);
            if (err)
                return err;
        }
    }
out:
    if (!partial)
        SetPageUptodate(page);
    return 0;
}

static int
move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
          pgoff_t orig_page_offset, int data_offset_in_page,
          int block_len_in_page, int uninit, int *err)
{
    struct inode *orig_inode = o_filp->f_dentry->d_inode;
    struct page *pagep[2] = {NULL, NULL};
    handle_t *handle;
    ext4_lblk_t orig_blk_offset;
    long long offs = orig_page_offset << PAGE_CACHE_SHIFT;
    unsigned long blocksize = orig_inode->i_sb->s_blocksize;
    unsigned int w_flags = 0;
    unsigned int tmp_data_size, data_size, replaced_size;
    int err2, jblocks, retries = 0;
    int replaced_count = 0;
    int from = data_offset_in_page << orig_inode->i_blkbits;
    int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;

    /*
     * It needs twice the amount of ordinary journal buffers because
     * inode and donor_inode may change each different metadata blocks.
     */
again:
    *err = 0;
    jblocks = ext4_writepage_trans_blocks(orig_inode) * 2;
    handle = ext4_journal_start(orig_inode, jblocks);
    if (IS_ERR(handle)) {
        *err = PTR_ERR(handle);
        return 0;
    }

    if (segment_eq(get_fs(), KERNEL_DS))
        w_flags |= AOP_FLAG_UNINTERRUPTIBLE;

    orig_blk_offset = orig_page_offset * blocks_per_page +
        data_offset_in_page;

    offs = (long long)orig_blk_offset << orig_inode->i_blkbits;

    /* Calculate data_size */
    if ((orig_blk_offset + block_len_in_page - 1) ==
        ((orig_inode->i_size - 1) >> orig_inode->i_blkbits)) {
        /* Replace the last block */
        tmp_data_size = orig_inode->i_size & (blocksize - 1);
        /*
         * If data_size equal zero, it shows data_size is multiples of
         * blocksize. So we set appropriate value.
         */
        if (tmp_data_size == 0)
            tmp_data_size = blocksize;

        data_size = tmp_data_size +
            ((block_len_in_page - 1) << orig_inode->i_blkbits);
    } else
        data_size = block_len_in_page << orig_inode->i_blkbits;

    replaced_size = data_size;

    *err = mext_page_double_lock(orig_inode, donor_inode, orig_page_offset,
                     pagep);
    if (unlikely(*err < 0))
        goto stop_journal;
    /*
     * If orig extent was uninitialized it can become initialized
     * at any time after i_data_sem was dropped, in order to
     * serialize with delalloc we have recheck extent while we
     * hold page's lock, if it is still the case data copy is not
     * necessary, just swap data blocks between orig and donor.
     */
    if (uninit) {
        double_down_write_data_sem(orig_inode, donor_inode);
        /* If any of extents in range became initialized we have to
         * fallback to data copying */
        uninit = mext_check_coverage(orig_inode, orig_blk_offset,
                         block_len_in_page, 1, err);
        if (*err)
            goto drop_data_sem;

        uninit &= mext_check_coverage(donor_inode, orig_blk_offset,
                          block_len_in_page, 1, err);
        if (*err)
            goto drop_data_sem;

        if (!uninit) {
            double_up_write_data_sem(orig_inode, donor_inode);
            goto data_copy;
        }
        if ((page_has_private(pagep[0]) &&
             !try_to_release_page(pagep[0], 0)) ||
            (page_has_private(pagep[1]) &&
             !try_to_release_page(pagep[1], 0))) {
            *err = -EBUSY;
            goto drop_data_sem;
        }
        replaced_count = mext_replace_branches(handle, orig_inode,
                        donor_inode, orig_blk_offset,
                        block_len_in_page, err);
    drop_data_sem:
        double_up_write_data_sem(orig_inode, donor_inode);
        goto unlock_pages;
    }
data_copy:
    *err = mext_page_mkuptodate(pagep[0], from, from + replaced_size);
    if (*err)
        goto unlock_pages;

    /* At this point all buffers in range are uptodate, old mapping layout
     * is no longer required, try to drop it now. */
    if ((page_has_private(pagep[0]) && !try_to_release_page(pagep[0], 0)) ||
        (page_has_private(pagep[1]) && !try_to_release_page(pagep[1], 0))) {
        *err = -EBUSY;
        goto unlock_pages;
    }

    replaced_count = mext_replace_branches(handle, orig_inode, donor_inode,
                           orig_blk_offset,
                           block_len_in_page, err);
    if (*err) {
        if (replaced_count) {
            block_len_in_page = replaced_count;
            replaced_size =
                block_len_in_page << orig_inode->i_blkbits;
        } else
            goto unlock_pages;
    }
    /* Perform all necessary steps similar write_begin()/write_end()
     * but keeping in mind that i_size will not change */
    *err = __block_write_begin(pagep[0], from, from + replaced_size,
                   ext4_get_block);
    if (!*err)
        *err = block_commit_write(pagep[0], from, from + replaced_size);

    if (unlikely(*err < 0))
        goto repair_branches;

    /* Even in case of data=writeback it is reasonable to pin
     * inode to transaction, to prevent unexpected data loss */
    *err = ext4_jbd2_file_inode(handle, orig_inode);

unlock_pages:
    unlock_page(pagep[0]);
    page_cache_release(pagep[0]);
    unlock_page(pagep[1]);
    page_cache_release(pagep[1]);
stop_journal:
    ext4_journal_stop(handle);
    /* Buffer was busy because probably is pinned to journal transaction,
     * force transaction commit may help to free it. */
    if (*err == -EBUSY && ext4_should_retry_alloc(orig_inode->i_sb,
                              &retries))
        goto again;
    return replaced_count;

repair_branches:
    /*
     * This should never ever happen!
     * Extents are swapped already, but we are not able to copy data.
     * Try to swap extents to it's original places
     */
    double_down_write_data_sem(orig_inode, donor_inode);
    replaced_count = mext_replace_branches(handle, donor_inode, orig_inode,
                           orig_blk_offset,
                           block_len_in_page, &err2);
    double_up_write_data_sem(orig_inode, donor_inode);
    if (replaced_count != block_len_in_page) {
        EXT4_ERROR_INODE_BLOCK(orig_inode, (sector_t)(orig_blk_offset),
                       "Unable to copy data block,"
                       " data will be lost.");
        *err = -EIO;
    }
    replaced_count = 0;
    goto unlock_pages;
}

static int
mext_check_arguments(struct inode *orig_inode,
             struct inode *donor_inode, __u64 orig_start,
             __u64 donor_start, __u64 *len)
{
    ext4_lblk_t orig_blocks, donor_blocks;
    unsigned int blkbits = orig_inode->i_blkbits;
    unsigned int blocksize = 1 << blkbits;

    if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
        ext4_debug("ext4 move extent: suid or sgid is set"
               " to donor file [ino:orig %lu, donor %lu]\n",
               orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }

    if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
        return -EPERM;

    /* Ext4 move extent does not support swapfile */
    if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
        ext4_debug("ext4 move extent: The argument files should "
            "not be swapfile [ino:orig %lu, donor %lu]\n",
            orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }

    /* Ext4 move extent supports only extent based file */
    if (!(ext4_test_inode_flag(orig_inode, EXT4_INODE_EXTENTS))) {
        ext4_debug("ext4 move extent: orig file is not extents "
            "based file [ino:orig %lu]\n", orig_inode->i_ino);
        return -EOPNOTSUPP;
    } else if (!(ext4_test_inode_flag(donor_inode, EXT4_INODE_EXTENTS))) {
        ext4_debug("ext4 move extent: donor file is not extents "
            "based file [ino:donor %lu]\n", donor_inode->i_ino);
        return -EOPNOTSUPP;
    }

    if ((!orig_inode->i_size) || (!donor_inode->i_size)) {
        ext4_debug("ext4 move extent: File size is 0 byte\n");
        return -EINVAL;
    }

    /* Start offset should be same */
    if (orig_start != donor_start) {
        ext4_debug("ext4 move extent: orig and donor's start "
            "offset are not same [ino:orig %lu, donor %lu]\n",
            orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }

    if ((orig_start >= EXT_MAX_BLOCKS) ||
        (*len > EXT_MAX_BLOCKS) ||
        (orig_start + *len >= EXT_MAX_BLOCKS))  {
        ext4_debug("ext4 move extent: Can't handle over [%u] blocks "
            "[ino:orig %lu, donor %lu]\n", EXT_MAX_BLOCKS,
            orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }

    if (orig_inode->i_size > donor_inode->i_size) {
        donor_blocks = (donor_inode->i_size + blocksize - 1) >> blkbits;
        /* TODO: eliminate this artificial restriction */
        if (orig_start >= donor_blocks) {
            ext4_debug("ext4 move extent: orig start offset "
            "[%llu] should be less than donor file blocks "
            "[%u] [ino:orig %lu, donor %lu]\n",
            orig_start, donor_blocks,
            orig_inode->i_ino, donor_inode->i_ino);
            return -EINVAL;
        }

        /* TODO: eliminate this artificial restriction */
        if (orig_start + *len > donor_blocks) {
            ext4_debug("ext4 move extent: End offset [%llu] should "
                "be less than donor file blocks [%u]."
                "So adjust length from %llu to %llu "
                "[ino:orig %lu, donor %lu]\n",
                orig_start + *len, donor_blocks,
                *len, donor_blocks - orig_start,
                orig_inode->i_ino, donor_inode->i_ino);
            *len = donor_blocks - orig_start;
        }
    } else {
        orig_blocks = (orig_inode->i_size + blocksize - 1) >> blkbits;
        if (orig_start >= orig_blocks) {
            ext4_debug("ext4 move extent: start offset [%llu] "
                "should be less than original file blocks "
                "[%u] [ino:orig %lu, donor %lu]\n",
                 orig_start, orig_blocks,
                orig_inode->i_ino, donor_inode->i_ino);
            return -EINVAL;
        }

        if (orig_start + *len > orig_blocks) {
            ext4_debug("ext4 move extent: Adjust length "
                "from %llu to %llu. Because it should be "
                "less than original file blocks "
                "[ino:orig %lu, donor %lu]\n",
                *len, orig_blocks - orig_start,
                orig_inode->i_ino, donor_inode->i_ino);
            *len = orig_blocks - orig_start;
        }
    }

    if (!*len) {
        ext4_debug("ext4 move extent: len should not be 0 "
            "[ino:orig %lu, donor %lu]\n", orig_inode->i_ino,
            donor_inode->i_ino);
        return -EINVAL;
    }

    return 0;
}

static void
mext_inode_double_lock(struct inode *inode1, struct inode *inode2)
{
    BUG_ON(inode1 == inode2);
    if (inode1 < inode2) {
        mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
        mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
    } else {
        mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
        mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
    }
}

static void
mext_inode_double_unlock(struct inode *inode1, struct inode *inode2)
{
    mutex_unlock(&inode1->i_mutex);
    mutex_unlock(&inode2->i_mutex);
}

int
ext4_move_extents(struct file *o_filp, struct file *d_filp,
         __u64 orig_start, __u64 donor_start, __u64 len,
         __u64 *moved_len)
{
    struct inode *orig_inode = o_filp->f_dentry->d_inode;
    struct inode *donor_inode = d_filp->f_dentry->d_inode;
    struct ext4_ext_path *orig_path = NULL, *holecheck_path = NULL;
    struct ext4_extent *ext_prev, *ext_cur, *ext_dummy;
    ext4_lblk_t block_start = orig_start;
    ext4_lblk_t block_end, seq_start, add_blocks, file_end, seq_blocks = 0;
    ext4_lblk_t rest_blocks;
    pgoff_t orig_page_offset = 0, seq_end_page;
    int ret, depth, last_extent = 0;
    int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
    int data_offset_in_page;
    int block_len_in_page;
    int uninit;

    if (orig_inode->i_sb != donor_inode->i_sb) {
        ext4_debug("ext4 move extent: The argument files "
            "should be in same FS [ino:orig %lu, donor %lu]\n",
            orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }

    /* orig and donor should be different inodes */
    if (orig_inode == donor_inode) {
        ext4_debug("ext4 move extent: The argument files should not "
            "be same inode [ino:orig %lu, donor %lu]\n",
            orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }

    /* Regular file check */
    if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
        ext4_debug("ext4 move extent: The argument files should be "
            "regular file [ino:orig %lu, donor %lu]\n",
            orig_inode->i_ino, donor_inode->i_ino);
        return -EINVAL;
    }
    /* TODO: This is non obvious task to swap blocks for inodes with full
       jornaling enabled */
    if (ext4_should_journal_data(orig_inode) ||
        ext4_should_journal_data(donor_inode)) {
        return -EINVAL;
    }
    /* Protect orig and donor inodes against a truncate */
    mext_inode_double_lock(orig_inode, donor_inode);

    /* Wait for all existing dio workers */
    ext4_inode_block_unlocked_dio(orig_inode);
    ext4_inode_block_unlocked_dio(donor_inode);
    inode_dio_wait(orig_inode);
    inode_dio_wait(donor_inode);

    /* Protect extent tree against block allocations via delalloc */
    double_down_write_data_sem(orig_inode, donor_inode);
    /* Check the filesystem environment whether move_extent can be done */
    ret = mext_check_arguments(orig_inode, donor_inode, orig_start,
                    donor_start, &len);
    if (ret)
        goto out;

    file_end = (i_size_read(orig_inode) - 1) >> orig_inode->i_blkbits;
    block_end = block_start + len - 1;
    if (file_end < block_end)
        len -= block_end - file_end;

    ret = get_ext_path(orig_inode, block_start, &orig_path);
    if (ret)
        goto out;

    /* Get path structure to check the hole */
    ret = get_ext_path(orig_inode, block_start, &holecheck_path);
    if (ret)
        goto out;

    depth = ext_depth(orig_inode);
    ext_cur = holecheck_path[depth].p_ext;

    /*
     * Get proper starting location of block replacement if block_start was
     * within the hole.
     */
    if (le32_to_cpu(ext_cur->ee_block) +
        ext4_ext_get_actual_len(ext_cur) - 1 < block_start) {
        /*
         * The hole exists between extents or the tail of
         * original file.
         */
        last_extent = mext_next_extent(orig_inode,
                    holecheck_path, &ext_cur);
        if (last_extent < 0) {
            ret = last_extent;
            goto out;
        }
        last_extent = mext_next_extent(orig_inode, orig_path,
                            &ext_dummy);
        if (last_extent < 0) {
            ret = last_extent;
            goto out;
        }
        seq_start = le32_to_cpu(ext_cur->ee_block);
    } else if (le32_to_cpu(ext_cur->ee_block) > block_start)
        /* The hole exists at the beginning of original file. */
        seq_start = le32_to_cpu(ext_cur->ee_block);
    else
        seq_start = block_start;

    /* No blocks within the specified range. */
    if (le32_to_cpu(ext_cur->ee_block) > block_end) {
        ext4_debug("ext4 move extent: The specified range of file "
                            "may be the hole\n");
        ret = -EINVAL;
        goto out;
    }

    /* Adjust start blocks */
    add_blocks = min(le32_to_cpu(ext_cur->ee_block) +
             ext4_ext_get_actual_len(ext_cur), block_end + 1) -
             max(le32_to_cpu(ext_cur->ee_block), block_start);

    while (!last_extent && le32_to_cpu(ext_cur->ee_block) <= block_end) {
        seq_blocks += add_blocks;

        /* Adjust tail blocks */
        if (seq_start + seq_blocks - 1 > block_end)
            seq_blocks = block_end - seq_start + 1;

        ext_prev = ext_cur;
        last_extent = mext_next_extent(orig_inode, holecheck_path,
                        &ext_cur);
        if (last_extent < 0) {
            ret = last_extent;
            break;
        }
        add_blocks = ext4_ext_get_actual_len(ext_cur);

        /*
         * Extend the length of contiguous block (seq_blocks)
         * if extents are contiguous.
         */
        if (ext4_can_extents_be_merged(orig_inode,
                           ext_prev, ext_cur) &&
            block_end >= le32_to_cpu(ext_cur->ee_block) &&
            !last_extent)
            continue;

        /* Is original extent is uninitialized */
        uninit = ext4_ext_is_uninitialized(ext_prev);

        data_offset_in_page = seq_start % blocks_per_page;

        /*
         * Calculate data blocks count that should be swapped
         * at the first page.
         */
        if (data_offset_in_page + seq_blocks > blocks_per_page) {
            /* Swapped blocks are across pages */
            block_len_in_page =
                    blocks_per_page - data_offset_in_page;
        } else {
            /* Swapped blocks are in a page */
            block_len_in_page = seq_blocks;
        }

        orig_page_offset = seq_start >>
                (PAGE_CACHE_SHIFT - orig_inode->i_blkbits);
        seq_end_page = (seq_start + seq_blocks - 1) >>
                (PAGE_CACHE_SHIFT - orig_inode->i_blkbits);
        seq_start = le32_to_cpu(ext_cur->ee_block);
        rest_blocks = seq_blocks;

        /*
         * Up semaphore to avoid following problems:
         * a. transaction deadlock among ext4_journal_start,
         *    ->write_begin via pagefault, and jbd2_journal_commit
         * b. racing with ->readpage, ->write_begin, and ext4_get_block
         *    in move_extent_per_page
         */
        double_up_write_data_sem(orig_inode, donor_inode);

        while (orig_page_offset <= seq_end_page) {

            /* Swap original branches with new branches */
            block_len_in_page = move_extent_per_page(
                        o_filp, donor_inode,
                        orig_page_offset,
                        data_offset_in_page,
                        block_len_in_page, uninit,
                        &ret);

            /* Count how many blocks we have exchanged */
            *moved_len += block_len_in_page;
            if (ret < 0)
                break;
            if (*moved_len > len) {
                EXT4_ERROR_INODE(orig_inode,
                    "We replaced blocks too much! "
                    "sum of replaced: %llu requested: %llu",
                    *moved_len, len);
                ret = -EIO;
                break;
            }

            orig_page_offset++;
            data_offset_in_page = 0;
            rest_blocks -= block_len_in_page;
            if (rest_blocks > blocks_per_page)
                block_len_in_page = blocks_per_page;
            else
                block_len_in_page = rest_blocks;
        }

        double_down_write_data_sem(orig_inode, donor_inode);
        if (ret < 0)
            break;

        /* Decrease buffer counter */
        if (holecheck_path)
            ext4_ext_drop_refs(holecheck_path);
        ret = get_ext_path(orig_inode, seq_start, &holecheck_path);
        if (ret)
            break;
        depth = holecheck_path->p_depth;

        /* Decrease buffer counter */
        if (orig_path)
            ext4_ext_drop_refs(orig_path);
        ret = get_ext_path(orig_inode, seq_start, &orig_path);
        if (ret)
            break;

        ext_cur = holecheck_path[depth].p_ext;
        add_blocks = ext4_ext_get_actual_len(ext_cur);
        seq_blocks = 0;

    }
out:
    if (*moved_len) {
        ext4_discard_preallocations(orig_inode);
        ext4_discard_preallocations(donor_inode);
    }

    if (orig_path) {
        ext4_ext_drop_refs(orig_path);
        kfree(orig_path);
    }
    if (holecheck_path) {
        ext4_ext_drop_refs(holecheck_path);
        kfree(holecheck_path);
    }
    double_up_write_data_sem(orig_inode, donor_inode);
    ext4_inode_resume_unlocked_dio(orig_inode);
    ext4_inode_resume_unlocked_dio(donor_inode);
    mext_inode_double_unlock(orig_inode, donor_inode);

    return ret;
}