[PATCH -next] btrfs: remove set but not used variable 'offset'

[YueHaibing]

Fixes gcc '-Wunused-but-set-variable' warning:

fs/btrfs/volumes.c: In function __btrfs_map_block:
fs/btrfs/volumes.c:6023:6: warning:
 variable offset set but not used [-Wunused-but-set-variable]

It is not used any more since commit 343abd1c0ca9 ("btrfs: Use
btrfs_get_io_geometry appropriately")

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
 fs/btrfs/volumes.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d1fd910..5d5a9ff 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6020,7 +6020,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 {
 	struct extent_map *em;
 	struct map_lookup *map;
-	u64 offset;
 	u64 stripe_offset;
 	u64 stripe_nr;
 	u64 stripe_len;
@@ -6055,7 +6054,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 	map = em->map_lookup;
 
 	*length = geom.len;
-	offset = geom.offset;
 	stripe_len = geom.stripe_len;
 	stripe_nr = geom.stripe_nr;
 	stripe_offset = geom.stripe_offset;
-- 
2.7.4