btrfs: cleanup for open-coded alignment

Though most of the btrfs codes are using ALIGN macro for page alignment,
there are still some codes using open-coded alignment like the
following:
------
        u64 mask = ((u64)root->stripesize - 1);
        u64 ret = (val + mask) & ~mask;
------
Or even hidden one:
------
        num_bytes = (end - start + blocksize) & ~(blocksize - 1);
------

Sometimes these open-coded alignment is not so easy to understand for
newbie like me.

This commit changes the open-coded alignment to the ALIGN macro for a
better readability.

Also there is a previous patch from David Sterba with similar changes,
but the patch is for 3.2 kernel and seems not merged.
http://www.spinics.net/lists/linux-btrfs/msg12747.html

Cc: David Sterba <dave@jikos.cz>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 538c5cfa005f..db72e0cc6f87 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4556,8 +4556,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
         num_stripes = 1;
         stripe_index = 0;
         stripe_nr_orig = stripe_nr;
-        stripe_nr_end = (offset + *length + map->stripe_len - 1) &
-                        (~(map->stripe_len - 1));
+        stripe_nr_end = ALIGN(offset + *length, map->stripe_len);
         do_div(stripe_nr_end, map->stripe_len);
         stripe_end_offset = stripe_nr_end * map->stripe_len -
                             (offset + *length);