ext4: online defrag -- Move the file data to the new blocks
>
> From: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
>
> Move the blocks on the temporary inode to the original inode
> by a page.
> 1. Read the file data from the old blocks to the page
> 2. Move the block on the temporary inode to the original inode
> 3. Write the file data on the page into the new blocks
>
> Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
> Signed-off-by: Takashi Sato <t-sato@xxxxxxxxxxxxx>
>
This patch is a bit of too big to review, will do it later....it would helpful to add more
comments as always, and small patches are prefered...
Mingming
> --
> fs/ext4/defrag.c | 738 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/ext4/extents.c | 2 +-
> fs/ext4/inode.c | 3 +-
> 3 files changed, 740 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/defrag.c b/fs/ext4/defrag.c
> index 6121705..19be87a 100644
> --- a/fs/ext4/defrag.c
> +++ b/fs/ext4/defrag.c
> @@ -127,6 +127,623 @@ int ext4_defrag_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
> }
>
> /**
> + * ext4_defrag_merge_across_blocks - Merge extents across leaf block
> + *
> + * @handle journal handle
> + * @inode target file's inode
> + * @o_start first original extent to be defraged
> + * @o_end last original extent to be defraged
> + * @start_ext first new extent to be merged
> + * @new_ext middle of new extent to be merged
> + * @end_ext last new extent to be merged
> + * @flag defrag mode (e.g. -f)
> + *
> + * This function returns 0 if succeed, otherwise returns error value.
> + */
> +static int
> +ext4_defrag_merge_across_blocks(handle_t *handle, struct inode *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,
> + int flag)
> +{
> + struct ext4_ext_path *org_path = NULL;
> + ext4_lblk_t eblock = 0;
> + int err = 0;
> + int new_flag = 0;
> + int end_flag = 0;
> + int defrag_flag;
> +
> + if (flag == DEFRAG_FORCE_VICTIM)
> + defrag_flag = 1;
> + else
> + defrag_flag = 0;
> +
> + if (le16_to_cpu(start_ext->ee_len) &&
> + le16_to_cpu(new_ext->ee_len) &&
> + le16_to_cpu(end_ext->ee_len)) {
> +
> + if ((o_start) == (o_end)) {
> +
> + /* start_ext new_ext end_ext
> + * dest |---------|-----------|--------|
> + * org |------------------------------|
> + */
> +
> + end_flag = 1;
> + } else {
> +
> + /* start_ext new_ext end_ext
> + * dest |---------|----------|---------|
> + * org |---------------|--------------|
> + */
> +
> + o_end->ee_block = end_ext->ee_block;
> + o_end->ee_len = end_ext->ee_len;
> + ext4_ext_store_pblock(o_end, ext_pblock(end_ext));
> + }
> +
> + o_start->ee_len = start_ext->ee_len;
> + new_flag = 1;
> +
> + } else if ((le16_to_cpu(start_ext->ee_len)) &&
> + (le16_to_cpu(new_ext->ee_len)) &&
> + (!le16_to_cpu(end_ext->ee_len)) &&
> + ((o_start) == (o_end))) {
> +
> + /* start_ext new_ext
> + * dest |--------------|---------------|
> + * org |------------------------------|
> + */
> +
> + o_start->ee_len = start_ext->ee_len;
> + new_flag = 1;
> +
> + } else if ((!le16_to_cpu(start_ext->ee_len)) &&
> + (le16_to_cpu(new_ext->ee_len)) &&
> + (le16_to_cpu(end_ext->ee_len)) &&
> + ((o_start) == (o_end))) {
> +
> + /* new_ext end_ext
> + * dest |--------------|---------------|
> + * org |------------------------------|
> + */
> +
> + o_end->ee_block = end_ext->ee_block;
> + o_end->ee_len = end_ext->ee_len;
> + ext4_ext_store_pblock(o_end, ext_pblock(end_ext));
> +
> + /*
> + * Set 0 to the extent block if new_ext was
> + * the first block.
> + */
> + if (!new_ext->ee_block)
> + eblock = 0;
> + else
> + eblock = le32_to_cpu(new_ext->ee_block);
> +
> + new_flag = 1;
> + } else {
> + printk(KERN_ERR "ext4 defrag: Unexpected merge case\n");
> + return -EIO;
> + }
> +
> + if (new_flag) {
> + org_path = ext4_ext_find_extent(inode, eblock, NULL);
> + if (IS_ERR(org_path)) {
> + err = PTR_ERR(org_path);
> + org_path = NULL;
> + goto out;
> + }
> + err = ext4_ext_insert_extent_defrag(handle, inode,
> + org_path, new_ext, defrag_flag);
> + if (err)
> + goto out;
> + }
> +
> + if (end_flag) {
> + org_path = ext4_ext_find_extent(inode,
> + le32_to_cpu(end_ext->ee_block) - 1, org_path);
> + if (IS_ERR(org_path)) {
> + err = PTR_ERR(org_path);
> + org_path = NULL;
> + goto out;
> + }
> + err = ext4_ext_insert_extent_defrag(handle, inode,
> + org_path, end_ext, defrag_flag);
> + if (err)
> + goto out;
> + }
> +out:
> + if (org_path) {
> + ext4_ext_drop_refs(org_path);
> + kfree(org_path);
> + }
> +
> + return err;
> +
> +}
> +
> +/**
> + * ext4_defrag_merge_inside_block - Merge new extent to the extent block
> + *
> + * @handle journal handle
> + * @inode target file's inode
> + * @o_start first original extent to be defraged
> + * @o_end last original extent to be merged
> + * @start_ext first new extent to be merged
> + * @new_ext middle of new extent to be merged
> + * @end_ext last new extent to be merged
> + * @eh extent header of target leaf block
> + * @replaced the number of blocks which will be replaced with new_ext
> + * @range_to_move used to decide how to merge
> + *
> + * This function always returns 0.
> + */
> +static int
> +ext4_defrag_merge_inside_block(handle_t *handle, struct inode *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_extent_header *eh,
> + ext4_fsblk_t replaced, int range_to_move)
> +{
> + int i = 0;
> + unsigned len;
> +
> + /* Move the existing extents */
> + if (range_to_move && o_end < EXT_LAST_EXTENT(eh)) {
> + len = EXT_LAST_EXTENT(eh) - (o_end + 1) + 1;
> + len = len * sizeof(struct ext4_extent);
> + memmove(o_end + 1 + range_to_move, o_end + 1, len);
> + }
> +
> + /* Insert start entry */
> + if (le16_to_cpu(start_ext->ee_len))
> + o_start[i++].ee_len = start_ext->ee_len;
> +
> + /* Insert new entry */
> + if (le16_to_cpu(new_ext->ee_len)) {
> + o_start[i].ee_block = new_ext->ee_block;
> + o_start[i].ee_len = cpu_to_le16(replaced);
> + ext4_ext_store_pblock(&o_start[i++], 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 */
> + eh->eh_entries
> + = cpu_to_le16(le16_to_cpu(eh->eh_entries) + range_to_move);
> +
> + return 0;
> +}
> +
> +/**
> + * ext4_defrag_merge_extents - Merge new extent
> + *
> + * @handle journal handle
> + * @inode target file's inode
> + * @org_path path indicates first extent to be defraged
> + * @o_start first original extent to be defraged
> + * @o_end last original extent to be defraged
> + * @start_ext first new extent to be merged
> + * @new_ext middle of new extent to be merged
> + * @end_ext last new extent to be merged
> + * @replaced the number of blocks which will be replaced with new_ext
> + * @flag defrag mode (e.g. -f)
> + *
> + * This function returns 0 if succeed, otherwise returns error value.
> + */
> +static int
> +ext4_defrag_merge_extents(handle_t *handle, struct inode *inode,
> + struct ext4_ext_path *org_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, ext4_fsblk_t replaced, int flag)
> +{
> + struct ext4_extent_header *eh;
> + unsigned need_slots, slots_range;
> + int range_to_move, depth, ret;
> +
> + /*
> + * The extents need to be inserted
> + * start_extent + new_extent + end_extent.
> + */
> + need_slots = (le16_to_cpu(start_ext->ee_len) ? 1 : 0) +
> + (le16_to_cpu(end_ext->ee_len) ? 1 : 0) +
> + (le16_to_cpu(new_ext->ee_len) ? 1 : 0);
> +
> + /* The number of slots between start and end */
> + slots_range = o_end - o_start + 1;
> +
> + /* Range to move the end of extent */
> + range_to_move = need_slots - slots_range;
> + depth = org_path->p_depth;
> + org_path += depth;
> + eh = org_path->p_hdr;
> +
> + if (depth) {
> + /* Register to journal */
> + ret = ext4_journal_get_write_access(handle, org_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 = ext4_defrag_merge_across_blocks(handle, inode, o_start,
> + o_end, start_ext, new_ext,
> + end_ext, flag);
> + if (ret < 0)
> + return ret;
> + } else {
> + ret = ext4_defrag_merge_inside_block(handle, inode, o_start,
> + o_end, start_ext, new_ext, end_ext,
> + eh, replaced, range_to_move);
> + if (ret < 0)
> + return ret;
> + }
> +
> + if (depth) {
> + ret = ext4_journal_dirty_metadata(handle, org_path->p_bh);
> + if (ret)
> + return ret;
> + } else {
> + ret = ext4_mark_inode_dirty(handle, inode);
> + if (ret < 0)
> + return ret;
> + }
> +
> + return 0;
> +
> +}
> +
> +/**
> + * ext4_defrag_leaf_block - Defragmentation for one leaf extent block
> + *
> + * @handle journal handle
> + * @org_inode target inode
> + * @org_path path indicates first extent to be defraged
> + * @dext destination extent
> + * @from start offset on the target file
> + * @flag defrag mode (e.g. -f)
> + *
> + * This function returns 0 if succeed, otherwise returns error value.
> + */
> +static int
> +ext4_defrag_leaf_block(handle_t *handle, struct inode *org_inode,
> + struct ext4_ext_path *org_path, struct ext4_extent *dext,
> + ext4_lblk_t *from, int flag)
> +{
> + unsigned long depth;
> + ext4_fsblk_t replaced = 0;
> + struct ext4_extent *oext, *o_start = NULL, *o_end = NULL, *prev_ext;
> + struct ext4_extent new_ext, start_ext, end_ext;
> + ext4_lblk_t new_end, lblock;
> + unsigned short len;
> + ext4_fsblk_t new_phys_end;
> + int ret;
> +
> + depth = ext_depth(org_inode);
> + start_ext.ee_len = end_ext.ee_len = 0;
> + o_start = o_end = oext = org_path[depth].p_ext;
> + ext4_ext_store_pblock(&new_ext, ext_pblock(dext));
> + new_ext.ee_len = dext->ee_len;
> + len = le16_to_cpu(new_ext.ee_len);
> + new_ext.ee_block = cpu_to_le32(*from);
> + lblock = le32_to_cpu(oext->ee_block);
> + new_end = le32_to_cpu(new_ext.ee_block)
> + + le16_to_cpu(new_ext.ee_len) - 1;
> + new_phys_end = ext_pblock(&new_ext)
> + + le16_to_cpu(new_ext.ee_len) - 1;
> +
> + /*
> + * First original extent
> + * dest |---------------|
> + * org |---------------|
> + */
> + if (le32_to_cpu(new_ext.ee_block) >
> + le32_to_cpu(oext->ee_block) &&
> + le32_to_cpu(new_ext.ee_block) <
> + le32_to_cpu(oext->ee_block)
> + + le16_to_cpu(oext->ee_len)) {
> + start_ext.ee_len = cpu_to_le32(le32_to_cpu(new_ext.ee_block)
> + - le32_to_cpu(oext->ee_block));
> + replaced += le16_to_cpu(oext->ee_len)
> + - le16_to_cpu(start_ext.ee_len);
> + } else if (oext > EXT_FIRST_EXTENT(org_path[depth].p_hdr)) {
> + /* We can merge previous extent. */
> + prev_ext = oext - 1;
> + if (((ext_pblock(prev_ext) + le32_to_cpu(prev_ext->ee_len))
> + == ext_pblock(&new_ext))
> + && (le32_to_cpu(prev_ext->ee_block)
> + + le32_to_cpu(prev_ext->ee_len)
> + == le32_to_cpu(new_ext.ee_block))) {
> + o_start = prev_ext;
> + start_ext.ee_len = cpu_to_le32(
> + le16_to_cpu(prev_ext->ee_len)
> + + le16_to_cpu(new_ext.ee_len));
> + new_ext.ee_len = 0;
> + }
> + }
> +
> + for (;;) {
> + /* The extent for destination must be found. */
> + BUG_ON(!oext || lblock != le32_to_cpu(oext->ee_block));
> + lblock += le16_to_cpu(oext->ee_len);
> +
> + /*
> + * Middle of original extent
> + * dest |-------------------|
> + * org |-----------------|
> + */
> + if (le32_to_cpu(new_ext.ee_block) <=
> + le32_to_cpu(oext->ee_block) &&
> + new_end >= le32_to_cpu(oext->ee_block)
> + + le16_to_cpu(oext->ee_len) - 1)
> + replaced += le16_to_cpu(oext->ee_len);
> +
> + /*
> + * Last original extent
> + * dest |----------------|
> + * org |---------------|
> + */
> + if (new_end >= le32_to_cpu(oext->ee_block) &&
> + new_end < le32_to_cpu(oext->ee_block)
> + + le16_to_cpu(oext->ee_len) - 1) {
> + end_ext.ee_len
> + = cpu_to_le16(le32_to_cpu(oext->ee_block)
> + + le16_to_cpu(oext->ee_len) - 1 - new_end);
> + ext4_ext_store_pblock(&end_ext, (ext_pblock(o_end)
> + + cpu_to_le16(oext->ee_len)
> + - cpu_to_le16(end_ext.ee_len)));
> + end_ext.ee_block
> + = cpu_to_le32(le32_to_cpu(o_end->ee_block)
> + + le16_to_cpu(oext->ee_len)
> + - le16_to_cpu(end_ext.ee_len));
> + replaced += le16_to_cpu(oext->ee_len)
> + - le16_to_cpu(end_ext.ee_len);
> + }
> +
> + /*
> + * Detected the block end, reached the number of replaced
> + * blocks to dext->ee_len. Then merge the extent.
> + */
> + if (oext == EXT_LAST_EXTENT(org_path[depth].p_hdr) ||
> + new_end <= le32_to_cpu(oext->ee_block)
> + + le16_to_cpu(oext->ee_len) - 1) {
> + ret = ext4_defrag_merge_extents(handle, org_inode,
> + org_path, o_start, o_end, &start_ext,
> + &new_ext, &end_ext, replaced, flag);
> + if (ret < 0)
> + return ret;
> +
> + /* All expected blocks are replaced */
> + if (le16_to_cpu(new_ext.ee_len) <= 0) {
> + if (DQUOT_ALLOC_BLOCK(org_inode, len))
> + return -EDQUOT;
> + return 0;
> + }
> +
> + /* Re-calculate new_ext */
> + new_ext.ee_len = cpu_to_le32(le16_to_cpu(new_ext.ee_len)
> + - replaced);
> + new_ext.ee_block =
> + cpu_to_le32(le32_to_cpu(new_ext.ee_block)
> + + replaced);
> + ext4_ext_store_pblock(&new_ext, ext_pblock(&new_ext)
> + + replaced);
> + replaced = 0;
> + start_ext.ee_len = end_ext.ee_len = 0;
> + o_start = NULL;
> +
> + /* All expected blocks are replaced. */
> + if (le16_to_cpu(new_ext.ee_len) <= 0) {
> + if (DQUOT_ALLOC_BLOCK(org_inode, len))
> + return -EDQUOT;
> + return 0;
> + }
> + }
> +
> + /* Get the next extent for original. */
> + if (org_path)
> + ext4_ext_drop_refs(org_path);
> + org_path = ext4_ext_find_extent(org_inode, lblock, org_path);
> + if (IS_ERR(org_path)) {
> + ret = PTR_ERR(org_path);
> + org_path = NULL;
> + return ret;
> + }
> + depth = ext_depth(org_inode);
> + oext = org_path[depth].p_ext;
> + if (oext->ee_block + oext->ee_len <= lblock)
> + return -ENOENT;
> +
> + o_end = oext;
> + if (!o_start)
> + o_start = oext;
> + }
> +}
> +
> +/**
> + * ext4_defrag_replace_branches - Replace original extents with new extents
> + *
> + * @handle journal handle
> + * @org_inode original inode
> + * @dest_inode temporary inode
> + * @from_page page offset of org_inode
> + * @dest_from_page page offset of dest_inode
> + * @count_page page count to be replaced
> + * @flag defrag mode (e.g. -f)
> + *
> + * This function returns 0 if succeed, otherwise returns error value.
> + * Replace extents for blocks from "from" to "from + count - 1".
> + */
> +static int
> +ext4_defrag_replace_branches(handle_t *handle, struct inode *org_inode,
> + struct inode *dest_inode, pgoff_t from_page,
> + pgoff_t dest_from_page, pgoff_t count_page, int flag)
> +{
> + struct ext4_ext_path *org_path = NULL;
> + struct ext4_ext_path *dest_path = NULL;
> + struct ext4_extent *oext, *dext, *swap_ext;
> + struct ext4_extent tmp_ext, tmp_ext2;
> + ext4_lblk_t from, count, dest_off, diff, org_diff;
> + int err = 0;
> + int depth;
> + int replaced_count = 0;
> +
> + from = (ext4_lblk_t)from_page <<
> + (PAGE_CACHE_SHIFT - dest_inode->i_blkbits);
> + count = (ext4_lblk_t)count_page <<
> + (PAGE_CACHE_SHIFT - dest_inode->i_blkbits);
> + dest_off = (ext4_lblk_t)dest_from_page <<
> + (PAGE_CACHE_SHIFT - dest_inode->i_blkbits);
> +
> + /* Get the original extent for the block "from" */
> + org_path = ext4_ext_find_extent(org_inode, from, NULL);
> + if (IS_ERR(org_path)) {
> + err = PTR_ERR(org_path);
> + org_path = NULL;
> + goto out;
> + }
> +
> + /* Get the destination extent for the head */
> + dest_path = ext4_ext_find_extent(dest_inode, dest_off, NULL);
> + if (IS_ERR(dest_path)) {
> + err = PTR_ERR(dest_path);
> + dest_path = NULL;
> + goto out;
> + }
> + depth = ext_depth(dest_inode);
> + dext = dest_path[depth].p_ext;
> + /* When dext is too large, pick up the target range. */
> + diff = dest_off - le32_to_cpu(dext->ee_block);
> + ext4_ext_store_pblock(&tmp_ext, ext_pblock(dext) + diff);
> + tmp_ext.ee_block = cpu_to_le32(le32_to_cpu(dext->ee_block) + diff);
> + tmp_ext.ee_len = cpu_to_le16(le16_to_cpu(dext->ee_len) - diff);
> + if (count < le16_to_cpu(tmp_ext.ee_len))
> + tmp_ext.ee_len = cpu_to_le16(count);
> + dext = &tmp_ext;
> +
> + depth = ext_depth(org_inode);
> + oext = org_path[depth].p_ext;
> + org_diff = from - le32_to_cpu(oext->ee_block);
> + ext4_ext_store_pblock(&tmp_ext2, ext_pblock(oext) + org_diff);
> + tmp_ext2.ee_block = tmp_ext.ee_block;
> +
> + /* Adjust extent length when blocksize != pagesize */
> + if (tmp_ext.ee_len <= (oext->ee_len - org_diff)) {
> + tmp_ext2.ee_len = tmp_ext.ee_len;
> + } else {
> + tmp_ext2.ee_len = oext->ee_len - org_diff;
> + tmp_ext.ee_len = tmp_ext2.ee_len;
> + }
> + swap_ext = &tmp_ext2;
> +
> + /* Loop for the destination extents */
> + while (1) {
> + /* The extent for destination must be found. */
> + BUG_ON(!dext || dest_off != le32_to_cpu(dext->ee_block));
> +
> + /* Loop for the original extent blocks */
> + err = ext4_defrag_leaf_block(handle, org_inode,
> + org_path, dext, &from, flag);
> + if (err < 0)
> + goto out;
> +
> + /*
> + * We need the function which fixes extent information for
> + * inserting.
> + * e.g. ext4_defrag_merge_extents()
> + */
> + err = ext4_defrag_leaf_block(handle, dest_inode,
> + dest_path, swap_ext, &dest_off, -1);
> + if (err < 0)
> + goto out;
> +
> + replaced_count += le16_to_cpu(dext->ee_len);
> + dest_off += le16_to_cpu(dext->ee_len);
> + from += le16_to_cpu(dext->ee_len);
> +
> + /* Already moved the expected blocks */
> + if (replaced_count >= count)
> + break;
> +
> + if (org_path)
> + ext4_ext_drop_refs(org_path);
> + org_path = ext4_ext_find_extent(org_inode, from, NULL);
> + if (IS_ERR(org_path)) {
> + err = PTR_ERR(org_path);
> + org_path = NULL;
> + goto out;
> + }
> + depth = ext_depth(org_inode);
> + oext = org_path[depth].p_ext;
> + if (oext->ee_block + oext->ee_len <= from) {
> + err = 0;
> + goto out;
> + }
> +
> + if (dest_path)
> + ext4_ext_drop_refs(dest_path);
> + dest_path = ext4_ext_find_extent(dest_inode, dest_off, NULL);
> + if (IS_ERR(dest_path)) {
> + err = PTR_ERR(dest_path);
> + dest_path = NULL;
> + goto out;
> + }
> + depth = ext_depth(dest_inode);
> + dext = dest_path[depth].p_ext;
> + if (dext->ee_block + dext->ee_len <= dest_off) {
> + err = 0;
> + goto out;
> + }
> +
> + /* When dext is too large, pick up the target range. */
> + diff = dest_off - le32_to_cpu(dext->ee_block);
> + ext4_ext_store_pblock(&tmp_ext, ext_pblock(dext) + diff);
> + tmp_ext.ee_block =
> + cpu_to_le32(le32_to_cpu(dext->ee_block) + diff);
> + tmp_ext.ee_len = cpu_to_le16(le16_to_cpu(dext->ee_len) - diff);
> +
> + if ((count - replaced_count) < le16_to_cpu(tmp_ext.ee_len))
> + tmp_ext.ee_len = count - replaced_count ;
> +
> + dext = &tmp_ext;
> +
> + org_diff = from - le32_to_cpu(oext->ee_block);
> + ext4_ext_store_pblock(&tmp_ext2, ext_pblock(oext) + org_diff);
> + tmp_ext2.ee_block = tmp_ext.ee_block;
> +
> + /* Adjust extent length when blocksize != pagesize */
> + if (tmp_ext.ee_len <= (oext->ee_len - org_diff)) {
> + tmp_ext2.ee_len = tmp_ext.ee_len;
> + } else {
> + tmp_ext2.ee_len = oext->ee_len - org_diff;
> + tmp_ext.ee_len = tmp_ext2.ee_len;
> + }
> + swap_ext = &tmp_ext2;
> + }
> +
> +out:
> + if (org_path) {
> + ext4_ext_drop_refs(org_path);
> + kfree(org_path);
> + }
> + if (dest_path) {
> + ext4_ext_drop_refs(dest_path);
> + kfree(dest_path);
> + }
> +
> + return err;
> +}
> +
> +/**
> * ext4_defrag_alloc_blocks - Allocate contiguous blocks to temporary inode
> *
> * @dest_inode temporary inode for multiple block allocation
> @@ -336,6 +953,127 @@ out2:
> }
>
> /**
> + * ext4_defrag_partial - Defrag a file per page
> + *
> + * @tmp_inode: the inode which has blocks to swap with original
> + * @filp: pointer to file
> + * @org_offset: page index on original file
> + * @dest_offset: page index on temporary file
> + * @flag: defrag mode (e.g. -f)
> + *
> + * This function returns 0 if succeeded, otherwise returns error value.
> + */
> +static int
> +ext4_defrag_partial(struct inode *tmp_inode, struct file *filp,
> + pgoff_t org_offset, pgoff_t dest_offset, int flag)
> +{
> + struct inode *inode = filp->f_dentry->d_inode;
> + struct address_space *mapping = inode->i_mapping;
> + struct buffer_head *bh;
> + struct page *page;
> + const struct address_space_operations *a_ops = mapping->a_ops;
> + handle_t *handle;
> + pgoff_t offset_in_page = PAGE_SIZE;
> + int jblocks;
> + int ret = 0;
> + int blocksize = inode->i_sb->s_blocksize;
> + int blocks_per_page = 0;
> + int i = 0;
> + long long offs = org_offset << PAGE_CACHE_SHIFT;
> + unsigned long blk_off = 0;
> + unsigned int w_flags = 0;
> + void *fsdata;
> +
> + /*
> + * It needs twice the amount of ordinary journal buffers because
> + * inode and tmp_inode may change each different metadata blocks.
> + */
> + jblocks = ext4_writepage_trans_blocks(inode) * 2;
> + handle = ext4_journal_start(inode, jblocks);
> + if (IS_ERR(handle)) {
> + ret = PTR_ERR(handle);
> + return ret;
> + }
> +
> + if (segment_eq(get_fs(), KERNEL_DS))
> + w_flags |= AOP_FLAG_UNINTERRUPTIBLE;
> +
> + if (org_offset == ((inode->i_size - 1) >> PAGE_CACHE_SHIFT)) {
> + offset_in_page = (inode->i_size & (PAGE_CACHE_SIZE - 1));
> + /*
> + * Set PAGE_CACHE_SIZE to offset_in_page not be 0
> + * if org_offset is the last page and i_size is
> + * multiples of PAGE_CACHE_SIZE.
> + */
> + if (offset_in_page == 0)
> + offset_in_page = PAGE_CACHE_SIZE;
> + }
> +
> + up_write(&EXT4_I(inode)->i_data_sem);
> + ret = a_ops->write_begin(filp, mapping, offs,
> + offset_in_page, w_flags, &page, &fsdata);
> + down_write(&EXT4_I(inode)->i_data_sem);
> +
> + if (unlikely(ret < 0))
> + goto out;
> +
> + if (!PageUptodate(page)) {
> + mapping->a_ops->readpage(filp, page);
> + lock_page(page);
> + }
> +
> + /*
> + * try_to_release_page() doesn't call relasepage in writeback mode.
> + * We should care about the order of writing to the same file
> + * by multiple defrag processes.
> + * It needs to call wait_on_page_writeback() to wait for the
> + * writeback of the page.
> + */
> + if (PageWriteback(page))
> + wait_on_page_writeback(page);
> +
> + /* Release old bh and drop refs */
> + try_to_release_page(page, 0);
> + ret = ext4_defrag_replace_branches(handle, inode, tmp_inode,
> + org_offset, dest_offset, 1, flag);
> +
> + if (ret < 0)
> + goto out;
> +
> + /* Clear the inode cache not to refer to the old data */
> + ext4_ext_invalidate_cache(inode);
> +
> + if (!page_has_buffers(page))
> + create_empty_buffers(page, 1 << inode->i_blkbits, 0);
> +
> + blocks_per_page = PAGE_SIZE / blocksize;
> + blk_off = org_offset * blocks_per_page;
> +
> + bh = page_buffers(page);
> + for (i = 0; i < blocks_per_page; i++) {
> + up_write(&EXT4_I(inode)->i_data_sem);
> + ret = ext4_get_block(inode, blk_off++, bh, 0);
> + down_write(&EXT4_I(inode)->i_data_sem);
> +
> + if (ret < 0)
> + goto out;
> +
> + if (bh->b_this_page != NULL)
> + bh = bh->b_this_page;
> + }
> +
> + ret = a_ops->write_end(filp, mapping, offs, offset_in_page,
> + offset_in_page, page, fsdata);
> +
> + if (unlikely(ret < 0))
> + goto out;
> +out:
> + ext4_journal_stop(handle);
> +
> + return (ret < 0 ? ret : 0);
> +}
> +
> +/**
> * ext4_defrag_new_extent_tree - Allocate contiguous blocks
> *
> * @inode: inode of the original file
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index f8828ff..dd8dc46 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1171,7 +1171,7 @@ ext4_ext_search_right(struct inode *inode, struct ext4_ext_path *path,
> * allocated block. Thus, index entries have to be consistent
> * with leaves.
> */
> -static ext4_lblk_t
> +ext4_lblk_t
> ext4_ext_next_allocated_block(struct ext4_ext_path *path)
> {
> int depth;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 0f252db..695877e 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -991,8 +991,7 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
> up_write((&EXT4_I(inode)->i_data_sem));
> return retval;
> }
> -
> -static int ext4_get_block(struct inode *inode, sector_t iblock,
> +int ext4_get_block(struct inode *inode, sector_t iblock,
> struct buffer_head *bh_result, int create)
> {
> handle_t *handle = ext4_journal_current_handle();
>
>
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