From: Zhang Yi <yi.zhang@huawei.com>

Now that we have mext_move_extent(), we can switch to this new interface
and deprecate move_extent_per_page(). First, after acquiring the
i_rwsem, we can directly use ext4_map_blocks() to obtain a contiguous
extent from the original inode as the extent to be moved. It can and
it's safe to get mapping information from the extent status tree without
needing to access the ondisk extent tree, because ext4_move_extent()
will check the sequence cookie under the folio lock. Then, after
populating the mext_data structure, we call ext4_move_extent() to move
the extent. Finally, the length of the extent will be adjusted in
mext.orig_map.m_len and the actual length moved is returned through
m_len.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/move_extent.c | 386 +++++-------------------------------------
 1 file changed, 42 insertions(+), 344 deletions(-)

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 4edb9a378db7..b478631e243c 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -20,29 +20,6 @@ struct mext_data {
 	ext4_lblk_t donor_lblk;		/* Start block of the donor file */
 };
 
-/**
- * get_ext_path() - Find an extent path for designated logical block number.
- * @inode:	inode to be searched
- * @lblock:	logical block number to find an extent path
- * @path:	pointer to an extent path
- *
- * ext4_find_extent wrapper. Return an extent path pointer on success,
- * or an error pointer on failure.
- */
-static inline struct ext4_ext_path *
-get_ext_path(struct inode *inode, ext4_lblk_t lblock,
-	     struct ext4_ext_path *path)
-{
-	path = ext4_find_extent(inode, lblock, path, EXT4_EX_NOCACHE);
-	if (IS_ERR(path))
-		return path;
-	if (path[ext_depth(inode)].p_ext == NULL) {
-		ext4_free_ext_path(path);
-		return ERR_PTR(-ENODATA);
-	}
-	return path;
-}
-
 /**
  * ext4_double_down_write_data_sem() - write lock two inodes's i_data_sem
  * @first: inode to be locked
@@ -59,7 +36,6 @@ ext4_double_down_write_data_sem(struct inode *first, struct inode *second)
 	} else {
 		down_write(&EXT4_I(second)->i_data_sem);
 		down_write_nested(&EXT4_I(first)->i_data_sem, I_DATA_SEM_OTHER);
-
 	}
 }
 
@@ -78,42 +54,6 @@ ext4_double_up_write_data_sem(struct inode *orig_inode,
 	up_write(&EXT4_I(donor_inode)->i_data_sem);
 }
 
-/**
- * mext_check_coverage - Check that all extents in range has the same type
- *
- * @inode:		inode in question
- * @from:		block offset of inode
- * @count:		block count to be checked
- * @unwritten:		extents expected to be unwritten
- * @err:		pointer to save error value
- *
- * Return 1 if all extents in range has expected type, and zero otherwise.
- */
-static int
-mext_check_coverage(struct inode *inode, ext4_lblk_t from, ext4_lblk_t count,
-		    int unwritten, int *err)
-{
-	struct ext4_ext_path *path = NULL;
-	struct ext4_extent *ext;
-	int ret = 0;
-	ext4_lblk_t last = from + count;
-	while (from < last) {
-		path = get_ext_path(inode, from, path);
-		if (IS_ERR(path)) {
-			*err = PTR_ERR(path);
-			return ret;
-		}
-		ext = path[ext_depth(inode)].p_ext;
-		if (unwritten != ext4_ext_is_unwritten(ext))
-			goto out;
-		from += ext4_ext_get_actual_len(ext);
-	}
-	ret = 1;
-out:
-	ext4_free_ext_path(path);
-	return ret;
-}
-
 /**
  * mext_folio_double_lock - Grab and lock folio on both @inode1 and @inode2
  *
@@ -363,7 +303,7 @@ static int mext_folio_mkwrite(struct inode *inode, struct folio *folio,
  * the replaced block count through m_len. Return 0 on success, and an error
  * code otherwise.
  */
-static __used int mext_move_extent(struct mext_data *mext, u64 *m_len)
+static int mext_move_extent(struct mext_data *mext, u64 *m_len)
 {
 	struct inode *orig_inode = mext->orig_inode;
 	struct inode *donor_inode = mext->donor_inode;
@@ -454,210 +394,6 @@ static __used int mext_move_extent(struct mext_data *mext, u64 *m_len)
 	goto unlock;
 }
 
-/**
- * move_extent_per_page - Move extent data per page
- *
- * @o_filp:			file structure of original file
- * @donor_inode:		donor inode
- * @orig_page_offset:		page index on original file
- * @donor_page_offset:		page index on donor file
- * @data_offset_in_page:	block index where data swapping starts
- * @block_len_in_page:		the number of blocks to be swapped
- * @unwritten:			orig extent is unwritten or not
- * @err:			pointer to save return value
- *
- * Save the data in original inode blocks and replace original inode extents
- * with donor inode extents by calling ext4_swap_extents().
- * Finally, write out the saved data in new original inode blocks. Return
- * replaced block count.
- */
-static int
-move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
-		     pgoff_t orig_page_offset, pgoff_t donor_page_offset,
-		     int data_offset_in_page,
-		     int block_len_in_page, int unwritten, int *err)
-{
-	struct inode *orig_inode = file_inode(o_filp);
-	struct folio *folio[2] = {NULL, NULL};
-	handle_t *handle;
-	ext4_lblk_t orig_blk_offset, donor_blk_offset;
-	unsigned long blocksize = orig_inode->i_sb->s_blocksize;
-	unsigned int tmp_data_size, data_size, replaced_size;
-	int i, err2, jblocks, retries = 0;
-	int replaced_count = 0;
-	int from;
-	int blocks_per_page = PAGE_SIZE >> orig_inode->i_blkbits;
-	struct super_block *sb = orig_inode->i_sb;
-	struct buffer_head *bh = NULL;
-
-	/*
-	 * 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_meta_trans_blocks(orig_inode, block_len_in_page,
-					 block_len_in_page) * 2;
-	handle = ext4_journal_start(orig_inode, EXT4_HT_MOVE_EXTENTS, jblocks);
-	if (IS_ERR(handle)) {
-		*err = PTR_ERR(handle);
-		return 0;
-	}
-
-	orig_blk_offset = orig_page_offset * blocks_per_page +
-		data_offset_in_page;
-
-	donor_blk_offset = donor_page_offset * blocks_per_page +
-		data_offset_in_page;
-
-	/* 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_folio_double_lock(orig_inode, donor_inode, orig_page_offset,
-				     donor_page_offset, folio);
-	if (unlikely(*err < 0))
-		goto stop_journal;
-	/*
-	 * If orig extent was unwritten 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 (unwritten) {
-		ext4_double_down_write_data_sem(orig_inode, donor_inode);
-		/* If any of extents in range became initialized we have to
-		 * fallback to data copying */
-		unwritten = mext_check_coverage(orig_inode, orig_blk_offset,
-						block_len_in_page, 1, err);
-		if (*err)
-			goto drop_data_sem;
-
-		unwritten &= mext_check_coverage(donor_inode, donor_blk_offset,
-						 block_len_in_page, 1, err);
-		if (*err)
-			goto drop_data_sem;
-
-		if (!unwritten) {
-			ext4_double_up_write_data_sem(orig_inode, donor_inode);
-			goto data_copy;
-		}
-		if (!filemap_release_folio(folio[0], 0) ||
-		    !filemap_release_folio(folio[1], 0)) {
-			*err = -EBUSY;
-			goto drop_data_sem;
-		}
-		replaced_count = ext4_swap_extents(handle, orig_inode,
-						   donor_inode, orig_blk_offset,
-						   donor_blk_offset,
-						   block_len_in_page, 1, err);
-	drop_data_sem:
-		ext4_double_up_write_data_sem(orig_inode, donor_inode);
-		goto unlock_folios;
-	}
-data_copy:
-	from = offset_in_folio(folio[0],
-			       orig_blk_offset << orig_inode->i_blkbits);
-	*err = mext_folio_mkuptodate(folio[0], from, from + replaced_size);
-	if (*err)
-		goto unlock_folios;
-
-	/* At this point all buffers in range are uptodate, old mapping layout
-	 * is no longer required, try to drop it now. */
-	if (!filemap_release_folio(folio[0], 0) ||
-	    !filemap_release_folio(folio[1], 0)) {
-		*err = -EBUSY;
-		goto unlock_folios;
-	}
-	ext4_double_down_write_data_sem(orig_inode, donor_inode);
-	replaced_count = ext4_swap_extents(handle, orig_inode, donor_inode,
-					       orig_blk_offset, donor_blk_offset,
-					   block_len_in_page, 1, err);
-	ext4_double_up_write_data_sem(orig_inode, donor_inode);
-	if (*err) {
-		if (replaced_count) {
-			block_len_in_page = replaced_count;
-			replaced_size =
-				block_len_in_page << orig_inode->i_blkbits;
-		} else
-			goto unlock_folios;
-	}
-	/* Perform all necessary steps similar write_begin()/write_end()
-	 * but keeping in mind that i_size will not change */
-	bh = folio_buffers(folio[0]);
-	if (!bh)
-		bh = create_empty_buffers(folio[0],
-				1 << orig_inode->i_blkbits, 0);
-	for (i = 0; i < from >> orig_inode->i_blkbits; i++)
-		bh = bh->b_this_page;
-	for (i = 0; i < block_len_in_page; i++) {
-		*err = ext4_get_block(orig_inode, orig_blk_offset + i, bh, 0);
-		if (*err < 0)
-			goto repair_branches;
-		bh = bh->b_this_page;
-	}
-
-	block_commit_write(folio[0], from, from + replaced_size);
-
-	/* Even in case of data=writeback it is reasonable to pin
-	 * inode to transaction, to prevent unexpected data loss */
-	*err = ext4_jbd2_inode_add_write(handle, orig_inode,
-			(loff_t)orig_page_offset << PAGE_SHIFT, replaced_size);
-
-unlock_folios:
-	folio_unlock(folio[0]);
-	folio_put(folio[0]);
-	folio_unlock(folio[1]);
-	folio_put(folio[1]);
-stop_journal:
-	ext4_journal_stop(handle);
-	if (*err == -ENOSPC &&
-	    ext4_should_retry_alloc(sb, &retries))
-		goto again;
-	/* Buffer was busy because probably is pinned to journal transaction,
-	 * force transaction commit may help to free it. */
-	if (*err == -EBUSY && retries++ < 4 && EXT4_SB(sb)->s_journal &&
-	    jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal))
-		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
-	 */
-	ext4_double_down_write_data_sem(orig_inode, donor_inode);
-	replaced_count = ext4_swap_extents(handle, donor_inode, orig_inode,
-					       orig_blk_offset, donor_blk_offset,
-					   block_len_in_page, 0, &err2);
-	ext4_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),
-				       EIO, "Unable to copy data block,"
-				       " data will be lost.");
-		*err = -EIO;
-	}
-	replaced_count = 0;
-	goto unlock_folios;
-}
-
 /*
  * Check the validity of the basic filesystem environment and the
  * inodes' support status.
@@ -819,106 +555,72 @@ static int mext_check_adjust_range(struct inode *orig_inode,
  *
  * This function returns 0 and moved block length is set in moved_len
  * if succeed, otherwise returns error value.
- *
  */
-int
-ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
-		  __u64 donor_blk, __u64 len, __u64 *moved_len)
+int ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
+		      __u64 donor_blk, __u64 len, __u64 *moved_len)
 {
 	struct inode *orig_inode = file_inode(o_filp);
 	struct inode *donor_inode = file_inode(d_filp);
-	struct ext4_ext_path *path = NULL;
-	int blocks_per_page = PAGE_SIZE >> orig_inode->i_blkbits;
-	ext4_lblk_t o_end, o_start = orig_blk;
-	ext4_lblk_t d_start = donor_blk;
+	struct mext_data mext;
+	struct super_block *sb = orig_inode->i_sb;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	int retries = 0;
+	u64 m_len;
 	int ret;
 
+	*moved_len = 0;
+
 	/* Protect orig and donor inodes against a truncate */
 	lock_two_nondirectories(orig_inode, donor_inode);
 
 	ret = mext_check_validity(orig_inode, donor_inode);
 	if (ret)
-		goto unlock;
+		goto out;
 
 	/* Wait for all existing dio workers */
 	inode_dio_wait(orig_inode);
 	inode_dio_wait(donor_inode);
 
-	/* Protect extent tree against block allocations via delalloc */
-	ext4_double_down_write_data_sem(orig_inode, donor_inode);
 	/* Check and adjust the specified move_extent range. */
 	ret = mext_check_adjust_range(orig_inode, donor_inode, orig_blk,
 				      donor_blk, &len);
 	if (ret)
 		goto out;
-	o_end = o_start + len;
 
-	*moved_len = 0;
-	while (o_start < o_end) {
-		struct ext4_extent *ex;
-		ext4_lblk_t cur_blk, next_blk;
-		pgoff_t orig_page_index, donor_page_index;
-		int offset_in_page;
-		int unwritten, cur_len;
-
-		path = get_ext_path(orig_inode, o_start, path);
-		if (IS_ERR(path)) {
-			ret = PTR_ERR(path);
+	mext.orig_inode = orig_inode;
+	mext.donor_inode = donor_inode;
+	while (len) {
+		mext.orig_map.m_lblk = orig_blk;
+		mext.orig_map.m_len = len;
+		mext.orig_map.m_flags = 0;
+		mext.donor_lblk = donor_blk;
+
+		ret = ext4_map_blocks(NULL, orig_inode, &mext.orig_map, 0);
+		if (ret < 0)
 			goto out;
-		}
-		ex = path[path->p_depth].p_ext;
-		cur_blk = le32_to_cpu(ex->ee_block);
-		cur_len = ext4_ext_get_actual_len(ex);
-		/* Check hole before the start pos */
-		if (cur_blk + cur_len - 1 < o_start) {
-			next_blk = ext4_ext_next_allocated_block(path);
-			if (next_blk == EXT_MAX_BLOCKS) {
-				ret = -ENODATA;
-				goto out;
-			}
-			d_start += next_blk - o_start;
-			o_start = next_blk;
-			continue;
-		/* Check hole after the start pos */
-		} else if (cur_blk > o_start) {
-			/* Skip hole */
-			d_start += cur_blk - o_start;
-			o_start = cur_blk;
-			/* Extent inside requested range ?*/
-			if (cur_blk >= o_end)
+
+		/* Skip moving if it is a hole or a delalloc extent. */
+		if (mext.orig_map.m_flags &
+		    (EXT4_MAP_MAPPED | EXT4_MAP_UNWRITTEN)) {
+			ret = mext_move_extent(&mext, &m_len);
+			if (ret == -ESTALE)
+				continue;
+			if (ret == -ENOSPC &&
+			    ext4_should_retry_alloc(sb, &retries))
+				continue;
+			if (ret == -EBUSY &&
+			    sbi->s_journal && retries++ < 4 &&
+			    jbd2_journal_force_commit_nested(sbi->s_journal))
+				continue;
+			if (ret)
 				goto out;
-		} else { /* in_range(o_start, o_blk, o_len) */
-			cur_len += cur_blk - o_start;
+
+			*moved_len += m_len;
+			retries = 0;
 		}
-		unwritten = ext4_ext_is_unwritten(ex);
-		if (o_end - o_start < cur_len)
-			cur_len = o_end - o_start;
-
-		orig_page_index = o_start >> (PAGE_SHIFT -
-					       orig_inode->i_blkbits);
-		donor_page_index = d_start >> (PAGE_SHIFT -
-					       donor_inode->i_blkbits);
-		offset_in_page = o_start % blocks_per_page;
-		if (cur_len > blocks_per_page - offset_in_page)
-			cur_len = blocks_per_page - offset_in_page;
-		/*
-		 * Up semaphore to avoid following problems:
-		 * a. transaction deadlock among ext4_journal_start,
-		 *    ->write_begin via pagefault, and jbd2_journal_commit
-		 * b. racing with ->read_folio, ->write_begin, and
-		 *    ext4_get_block in move_extent_per_page
-		 */
-		ext4_double_up_write_data_sem(orig_inode, donor_inode);
-		/* Swap original branches with new branches */
-		*moved_len += move_extent_per_page(o_filp, donor_inode,
-				     orig_page_index, donor_page_index,
-				     offset_in_page, cur_len,
-				     unwritten, &ret);
-		ext4_double_down_write_data_sem(orig_inode, donor_inode);
-		if (ret < 0)
-			break;
-		o_start += cur_len;
-		d_start += cur_len;
+		orig_blk += mext.orig_map.m_len;
+		donor_blk += mext.orig_map.m_len;
+		len -= mext.orig_map.m_len;
 	}
 
 out:
@@ -927,10 +629,6 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 		ext4_discard_preallocations(donor_inode);
 	}
 
-	ext4_free_ext_path(path);
-	ext4_double_up_write_data_sem(orig_inode, donor_inode);
-unlock:
 	unlock_two_nondirectories(orig_inode, donor_inode);
-
 	return ret;
 }
-- 
2.46.1