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[stable-5.4,3/6] btrfs: volumes: Use more straightforward way to calculate map length

Message ID b15e98a7c6129f8b5f0a7748061e93865bb944e1.1599750901.git.anand.jain@oracle.com
State New
Headers show
Series [stable-5.4,1/6] Btrfs: send, allow clone operations within the same file | expand

Commit Message

Anand Jain Oct. 8, 2020, 10:59 a.m. UTC 
From: Qu Wenruo <wqu@suse.com>

commit 2d974619a77f106f3d1341686dea95c0eaad601f upstream.

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>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 196ddbcd2936..1dba45d43485 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5712,7 +5712,7 @@  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;
 	/*