btrfs: volumes: Use more straightforward way to calculate map length

The old code goes:

 	offset = logical - em->start;
	length = min_t(u64, em->len - offset, length);

Where @length calculation is dependent on offset, it can take reader
several more seconds to find it's just the same code as:

 	offset = logical - em->start;
	length = min_t(u64, em->start + em->len - logical, length);

Use above code to make the length calculate independent from other
variable, thus slightly increase the readability.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2019-10-23 21:57:26 +08:00 committed by David Sterba
parent 153a6d2999
commit 2d974619a7

View File

@ -5412,7 +5412,7 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
}
offset = logical - em->start;
length = min_t(u64, em->len - offset, length);
length = min_t(u64, em->start + em->len - logical, length);
stripe_len = map->stripe_len;
/*