fs/ext4/migrate.c - linux - Git at Google

 // SPDX-License-Identifier: LGPL-2.1
 /*
  * Copyright IBM Corporation, 2007
  * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
  *
  */

 #include <linux/slab.h>
 #include "ext4_jbd2.h"
 #include "ext4_extents.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);
 	/* Locking only for convenience since we are operating on temp inode */
 	down_write(&EXT4_I(inode)->i_data_sem);
 	path = ext4_find_extent(inode, lb->first_block, NULL, 0);
 	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 accumulate extra
 	 * credit. But below we try to not accumulate 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);

 	retval = ext4_datasem_ensure_credits(handle, inode, needed, needed, 0);
 	if (retval < 0)
 		goto err_out;
 	retval = ext4_ext_insert_extent(handle, inode, &path, &newext, 0);
 err_out:
 	up_write((&EXT4_I(inode)->i_data_sem));
 	ext4_free_ext_path(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 = ext4_sb_bread(inode->i_sb, pblock, 0);
 	if (IS_ERR(bh))
 		return PTR_ERR(bh);

 	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 = ext4_sb_bread(inode->i_sb, pblock, 0);
 	if (IS_ERR(bh))
 		return PTR_ERR(bh);

 	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 = ext4_sb_bread(inode->i_sb, pblock, 0);
 	if (IS_ERR(bh))
 		return PTR_ERR(bh);

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

 	bh = ext4_sb_bread(sb, le32_to_cpu(i_data), 0);
 	if (IS_ERR(bh))
 		return PTR_ERR(bh);

 	tmp_idata = (__le32 *)bh->b_data;
 	for (i = 0; i < max_entries; i++) {
 		if (tmp_idata[i]) {
 			err = ext4_journal_ensure_credits(handle,
 				EXT4_RESERVE_TRANS_BLOCKS,
 				ext4_free_metadata_revoke_credits(sb, 1));
 			if (err < 0) {
 				put_bh(bh);
 				return err;
 			}
 			ext4_free_blocks(handle, inode, NULL,
 					 le32_to_cpu(tmp_idata[i]), 1,
 					 EXT4_FREE_BLOCKS_METADATA |
 					 EXT4_FREE_BLOCKS_FORGET);
 		}
 	}
 	put_bh(bh);
 	err = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
 				ext4_free_metadata_revoke_credits(sb, 1));
 	if (err < 0)
 		return err;
 	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 = ext4_sb_bread(inode->i_sb, le32_to_cpu(i_data), 0);
 	if (IS_ERR(bh))
 		return PTR_ERR(bh);

 	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);
 	retval = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
 			ext4_free_metadata_revoke_credits(inode->i_sb, 1));
 	if (retval < 0)
 		return retval;
 	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]) {
 		retval = ext4_journal_ensure_credits(handle,
 			EXT4_RESERVE_TRANS_BLOCKS,
 			ext4_free_metadata_revoke_credits(inode->i_sb, 1));
 		if (retval < 0)
 			return retval;
 		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, retval2 = 0;
 	__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_ensure_credits(handle, 1, 0);
 	if (retval < 0)
 		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 original 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);
 	retval2 = ext4_mark_inode_dirty(handle, inode);
 	if (unlikely(retval2 && !retval))
 		retval = retval2;

 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 = ext4_sb_bread(inode->i_sb, block, 0);
 	if (IS_ERR(bh))
 		return PTR_ERR(bh);

 	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) {
 				put_bh(bh);
 				return retval;
 			}
 		}
 	}
 	put_bh(bh);
 	retval = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
 			ext4_free_metadata_revoke_credits(inode->i_sb, 1));
 	if (retval < 0)
 		return retval;
 	ext4_free_blocks(handle, inode, NULL, block, 1,
 			 EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
 	return 0;
 }

 /*
  * 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)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	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, tmp_csum_seed;
 	uid_t owner[2];

 	/*
 	 * If the filesystem does not support extents, or the inode
 	 * already is extent-based, error out.
 	 */
 	if (!ext4_has_feature_extents(inode->i_sb) ||
 	    (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;

 	percpu_down_write(&sbi->s_writepages_rwsem);

 	/*
 	 * Worst case we can touch the allocation bitmaps and a block
 	 * group descriptor block.  We do need to worry about
 	 * credits for modifying the quota inode.
 	 */
 	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE,
 		3 + EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb));

 	if (IS_ERR(handle)) {
 		retval = PTR_ERR(handle);
 		goto out_unlock;
 	}
 	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, d_inode(inode->i_sb->s_root),
 				   S_IFREG, NULL, goal, owner, 0);
 	if (IS_ERR(tmp_inode)) {
 		retval = PTR_ERR(tmp_inode);
 		ext4_journal_stop(handle);
 		goto out_unlock;
 	}
 	/*
 	 * Use the correct seed for checksum (i.e. the seed from 'inode').  This
 	 * is so that the metadata blocks will have the correct checksum after
 	 * the migration.
 	 */
 	ei = EXT4_I(inode);
 	tmp_csum_seed = EXT4_I(tmp_inode)->i_csum_seed;
 	EXT4_I(tmp_inode)->i_csum_seed = ei->i_csum_seed;
 	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_journal_stop(handle);

 	/*
 	 * start with one credit accounted for
 	 * superblock modification.
 	 *
 	 * For the tmp_inode we already have committed the
 	 * transaction that created the inode. Later as and
 	 * when we add extents we extent the journal
 	 */
 	/*
 	 * Even though we take i_rwsem 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, EXT4_HT_MIGRATE, 1);
 	if (IS_ERR(handle)) {
 		retval = PTR_ERR(handle);
 		goto out_tmp_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. */
 	retval = ext4_journal_ensure_credits(handle, 1, 0);
 	if (retval < 0)
 		goto out_stop;
 	/*
 	 * 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_evict_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;
 	EXT4_I(tmp_inode)->i_csum_seed = tmp_csum_seed;

 	/* Reset the extent details */
 	ext4_ext_tree_init(handle, tmp_inode);
 out_stop:
 	ext4_journal_stop(handle);
 out_tmp_inode:
 	unlock_new_inode(tmp_inode);
 	iput(tmp_inode);
 out_unlock:
 	percpu_up_write(&sbi->s_writepages_rwsem);
 	return retval;
 }

 /*
  * Migrate a simple extent-based inode to use the i_blocks[] array
  */
 int ext4_ind_migrate(struct inode *inode)
 {
 	struct ext4_extent_header	*eh;
 	struct ext4_sb_info		*sbi = EXT4_SB(inode->i_sb);
 	struct ext4_super_block		*es = sbi->s_es;
 	struct ext4_inode_info		*ei = EXT4_I(inode);
 	struct ext4_extent		*ex;
 	unsigned int			i, len;
 	ext4_lblk_t			start, end;
 	ext4_fsblk_t			blk;
 	handle_t			*handle;
 	int				ret, ret2 = 0;

 	if (!ext4_has_feature_extents(inode->i_sb) ||
 	    (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
 		return -EINVAL;

 	if (ext4_has_feature_bigalloc(inode->i_sb))
 		return -EOPNOTSUPP;

 	/*
 	 * In order to get correct extent info, force all delayed allocation
 	 * blocks to be allocated, otherwise delayed allocation blocks may not
 	 * be reflected and bypass the checks on extent header.
 	 */
 	if (test_opt(inode->i_sb, DELALLOC))
 		ext4_alloc_da_blocks(inode);

 	percpu_down_write(&sbi->s_writepages_rwsem);

 	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
 		goto out_unlock;
 	}

 	down_write(&EXT4_I(inode)->i_data_sem);
 	ret = ext4_ext_check_inode(inode);
 	if (ret)
 		goto errout;

 	eh = ext_inode_hdr(inode);
 	ex  = EXT_FIRST_EXTENT(eh);
 	if (ext4_blocks_count(es) > EXT4_MAX_BLOCK_FILE_PHYS ||
 	    eh->eh_depth != 0 || le16_to_cpu(eh->eh_entries) > 1) {
 		ret = -EOPNOTSUPP;
 		goto errout;
 	}
 	if (eh->eh_entries == 0)
 		blk = len = start = end = 0;
 	else {
 		len = le16_to_cpu(ex->ee_len);
 		blk = ext4_ext_pblock(ex);
 		start = le32_to_cpu(ex->ee_block);
 		end = start + len - 1;
 		if (end >= EXT4_NDIR_BLOCKS) {
 			ret = -EOPNOTSUPP;
 			goto errout;
 		}
 	}

 	ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
 	memset(ei->i_data, 0, sizeof(ei->i_data));
 	for (i = start; i <= end; i++)
 		ei->i_data[i] = cpu_to_le32(blk++);
 	ret2 = ext4_mark_inode_dirty(handle, inode);
 	if (unlikely(ret2 && !ret))
 		ret = ret2;
 errout:
 	ext4_journal_stop(handle);
 	up_write(&EXT4_I(inode)->i_data_sem);
 out_unlock:
 	percpu_up_write(&sbi->s_writepages_rwsem);
 	return ret;
 }
	// SPDX-License-Identifier: LGPL-2.1
	/*
	* Copyright IBM Corporation, 2007
	* Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
	*
	*/

	#include <linux/slab.h>
	#include "ext4_jbd2.h"
	#include "ext4_extents.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);
	/* Locking only for convenience since we are operating on temp inode */
	down_write(&EXT4_I(inode)->i_data_sem);
	path = ext4_find_extent(inode, lb->first_block, NULL, 0);
	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 accumulate extra
	* credit. But below we try to not accumulate 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);

	retval = ext4_datasem_ensure_credits(handle, inode, needed, needed, 0);
	if (retval < 0)
	goto err_out;
	retval = ext4_ext_insert_extent(handle, inode, &path, &newext, 0);
	err_out:
	up_write((&EXT4_I(inode)->i_data_sem));
	ext4_free_ext_path(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 = ext4_sb_bread(inode->i_sb, pblock, 0);
	if (IS_ERR(bh))
	return PTR_ERR(bh);

	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 = ext4_sb_bread(inode->i_sb, pblock, 0);
	if (IS_ERR(bh))
	return PTR_ERR(bh);

	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 = ext4_sb_bread(inode->i_sb, pblock, 0);
	if (IS_ERR(bh))
	return PTR_ERR(bh);

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

	bh = ext4_sb_bread(sb, le32_to_cpu(i_data), 0);
	if (IS_ERR(bh))
	return PTR_ERR(bh);

	tmp_idata = (__le32 *)bh->b_data;
	for (i = 0; i < max_entries; i++) {
	if (tmp_idata[i]) {
	err = ext4_journal_ensure_credits(handle,
	EXT4_RESERVE_TRANS_BLOCKS,
	ext4_free_metadata_revoke_credits(sb, 1));
	if (err < 0) {
	put_bh(bh);
	return err;
	}
	ext4_free_blocks(handle, inode, NULL,
	le32_to_cpu(tmp_idata[i]), 1,
	EXT4_FREE_BLOCKS_METADATA \|
	EXT4_FREE_BLOCKS_FORGET);
	}
	}
	put_bh(bh);
	err = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
	ext4_free_metadata_revoke_credits(sb, 1));
	if (err < 0)
	return err;
	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 = ext4_sb_bread(inode->i_sb, le32_to_cpu(i_data), 0);
	if (IS_ERR(bh))
	return PTR_ERR(bh);

	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);
	retval = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
	ext4_free_metadata_revoke_credits(inode->i_sb, 1));
	if (retval < 0)
	return retval;
	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]) {
	retval = ext4_journal_ensure_credits(handle,
	EXT4_RESERVE_TRANS_BLOCKS,
	ext4_free_metadata_revoke_credits(inode->i_sb, 1));
	if (retval < 0)
	return retval;
	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, retval2 = 0;
	__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_ensure_credits(handle, 1, 0);
	if (retval < 0)
	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 original 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);
	retval2 = ext4_mark_inode_dirty(handle, inode);
	if (unlikely(retval2 && !retval))
	retval = retval2;

	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 = ext4_sb_bread(inode->i_sb, block, 0);
	if (IS_ERR(bh))
	return PTR_ERR(bh);

	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) {
	put_bh(bh);
	return retval;
	}
	}
	}
	put_bh(bh);
	retval = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
	ext4_free_metadata_revoke_credits(inode->i_sb, 1));
	if (retval < 0)
	return retval;
	ext4_free_blocks(handle, inode, NULL, block, 1,
	EXT4_FREE_BLOCKS_METADATA \| EXT4_FREE_BLOCKS_FORGET);
	return 0;
	}

	/*
	* 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)
	{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	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, tmp_csum_seed;
	uid_t owner[2];

	/*
	* If the filesystem does not support extents, or the inode
	* already is extent-based, error out.
	*/
	if (!ext4_has_feature_extents(inode->i_sb) \|\|
	(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;

	percpu_down_write(&sbi->s_writepages_rwsem);

	/*
	* Worst case we can touch the allocation bitmaps and a block
	* group descriptor block. We do need to worry about
	* credits for modifying the quota inode.
	*/
	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE,
	3 + EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb));

	if (IS_ERR(handle)) {
	retval = PTR_ERR(handle);
	goto out_unlock;
	}
	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, d_inode(inode->i_sb->s_root),
	S_IFREG, NULL, goal, owner, 0);
	if (IS_ERR(tmp_inode)) {
	retval = PTR_ERR(tmp_inode);
	ext4_journal_stop(handle);
	goto out_unlock;
	}
	/*
	* Use the correct seed for checksum (i.e. the seed from 'inode'). This
	* is so that the metadata blocks will have the correct checksum after
	* the migration.
	*/
	ei = EXT4_I(inode);
	tmp_csum_seed = EXT4_I(tmp_inode)->i_csum_seed;
	EXT4_I(tmp_inode)->i_csum_seed = ei->i_csum_seed;
	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_journal_stop(handle);

	/*
	* start with one credit accounted for
	* superblock modification.
	*
	* For the tmp_inode we already have committed the
	* transaction that created the inode. Later as and
	* when we add extents we extent the journal
	*/
	/*
	* Even though we take i_rwsem 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, EXT4_HT_MIGRATE, 1);
	if (IS_ERR(handle)) {
	retval = PTR_ERR(handle);
	goto out_tmp_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. */
	retval = ext4_journal_ensure_credits(handle, 1, 0);
	if (retval < 0)
	goto out_stop;
	/*
	* 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_evict_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;
	EXT4_I(tmp_inode)->i_csum_seed = tmp_csum_seed;

	/* Reset the extent details */
	ext4_ext_tree_init(handle, tmp_inode);
	out_stop:
	ext4_journal_stop(handle);
	out_tmp_inode:
	unlock_new_inode(tmp_inode);
	iput(tmp_inode);
	out_unlock:
	percpu_up_write(&sbi->s_writepages_rwsem);
	return retval;
	}

	/*
	* Migrate a simple extent-based inode to use the i_blocks[] array
	*/
	int ext4_ind_migrate(struct inode *inode)
	{
	struct ext4_extent_header *eh;
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct ext4_super_block *es = sbi->s_es;
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_extent *ex;
	unsigned int i, len;
	ext4_lblk_t start, end;
	ext4_fsblk_t blk;
	handle_t *handle;
	int ret, ret2 = 0;

	if (!ext4_has_feature_extents(inode->i_sb) \|\|
	(!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
	return -EINVAL;

	if (ext4_has_feature_bigalloc(inode->i_sb))
	return -EOPNOTSUPP;

	/*
	* In order to get correct extent info, force all delayed allocation
	* blocks to be allocated, otherwise delayed allocation blocks may not
	* be reflected and bypass the checks on extent header.
	*/
	if (test_opt(inode->i_sb, DELALLOC))
	ext4_alloc_da_blocks(inode);

	percpu_down_write(&sbi->s_writepages_rwsem);

	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
	if (IS_ERR(handle)) {
	ret = PTR_ERR(handle);
	goto out_unlock;
	}

	down_write(&EXT4_I(inode)->i_data_sem);
	ret = ext4_ext_check_inode(inode);
	if (ret)
	goto errout;

	eh = ext_inode_hdr(inode);
	ex = EXT_FIRST_EXTENT(eh);
	if (ext4_blocks_count(es) > EXT4_MAX_BLOCK_FILE_PHYS \|\|
	eh->eh_depth != 0 \|\| le16_to_cpu(eh->eh_entries) > 1) {
	ret = -EOPNOTSUPP;
	goto errout;
	}
	if (eh->eh_entries == 0)
	blk = len = start = end = 0;
	else {
	len = le16_to_cpu(ex->ee_len);
	blk = ext4_ext_pblock(ex);
	start = le32_to_cpu(ex->ee_block);
	end = start + len - 1;
	if (end >= EXT4_NDIR_BLOCKS) {
	ret = -EOPNOTSUPP;
	goto errout;
	}
	}

	ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
	memset(ei->i_data, 0, sizeof(ei->i_data));
	for (i = start; i <= end; i++)
	ei->i_data[i] = cpu_to_le32(blk++);
	ret2 = ext4_mark_inode_dirty(handle, inode);
	if (unlikely(ret2 && !ret))
	ret = ret2;
	errout:
	ext4_journal_stop(handle);
	up_write(&EXT4_I(inode)->i_data_sem);
	out_unlock:
	percpu_up_write(&sbi->s_writepages_rwsem);
	return ret;
	}