Revert "btrfs-progs: convert: make sure the length of data chunks are also stripe aligned"

This reverts commit 136c586.

[BUG]
There is a bug report that kernel is rejecting a converted btrfs that
has dev extents beyond device boundary.

The involved device extent is at 999627694980, length is 30924800,
meanwhile the device is 999658557440.

The device is size not aligned to 64K, meanwhile the dev extent is
aligned to 64K.

[CAUSE]
For converted btrfs, the source fs has all its freedom to choose its
size, as long as it's aligned to the fs block size.

So when adding new converted data block groups we need to do extra
alignment, but in make_convert_data_block_groups() we are rounding up
the end, which can exceed the device size.

[FIX]
The original commit 136c586 ("btrfs-progs: convert: make sure the
length of data chunks are also stripe aligned") is only a workaround to
address a kernel bug.

But since the kernel bug is long fixed, there isn't really much need to
do the workaround, just revert it to avoid the dev extent to go beyond
device size.

Pull-request: #1056
Reported-by: Andieqqq <[email protected]>
Signed-off-by: Qu Wenruo <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: adam900710

convert/main.c

@@ -948,8 +948,7 @@ static int make_convert_data_block_groups(struct btrfs_trans_handle *trans,
 			u64 cur_backup = cur;
 
 			len = min(max_chunk_size,
-				  round_up(cache->start + cache->size,
-					   BTRFS_STRIPE_LEN) - cur);
+				  cache->start + cache->size - cur);
 			ret = btrfs_alloc_data_chunk(trans, fs_info, &cur_backup, len);
 			if (ret < 0)
 				break;