btrfs: cleanup the bytenr usage inside btrfs_extent_item_to_extent_map()

[HICCUP]
Before commit 85de2be7129c ("btrfs: remove extent_map::block_start
member"), we utilized @bytenr variable inside
btrfs_extent_item_to_extent_map() to calculate block_start.

But that commit removed block_start completely, we have no need to
advance @bytenr at all.

[ENHANCEMENT]
- Rename @bytenr as @disk_bytenr
- Only declare @disk_bytenr inside the if branch
- Make @disk_bytenr const and remove the modification on it

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 55703c833f3d1d193a109d03d5b6b00cc27c79aa..2cc61c792ee68f157bd9e870a937566d760493b5 100644 (file)
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -1281,7 +1281,6 @@ void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
        const int slot = path->slots[0];
        struct btrfs_key key;
        u64 extent_start;
-       u64 bytenr;
        u8 type = btrfs_file_extent_type(leaf, fi);
        int compress_type = btrfs_file_extent_compression(leaf, fi);
 
@@ -1291,22 +1290,22 @@ void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
        em->generation = btrfs_file_extent_generation(leaf, fi);
        if (type == BTRFS_FILE_EXTENT_REG ||
            type == BTRFS_FILE_EXTENT_PREALLOC) {
+               const u64 disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+
                em->start = extent_start;
                em->len = btrfs_file_extent_end(path) - extent_start;
-               bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
-               if (bytenr == 0) {
+               if (disk_bytenr == 0) {
                        em->disk_bytenr = EXTENT_MAP_HOLE;
                        em->disk_num_bytes = 0;
                        em->offset = 0;
                        return;
                }
-               em->disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+               em->disk_bytenr = disk_bytenr;
                em->disk_num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
                em->offset = btrfs_file_extent_offset(leaf, fi);
                if (compress_type != BTRFS_COMPRESS_NONE) {
                        extent_map_set_compression(em, compress_type);
                } else {
-                       bytenr += btrfs_file_extent_offset(leaf, fi);
                        if (type == BTRFS_FILE_EXTENT_PREALLOC)
                                em->flags |= EXTENT_FLAG_PREALLOC;
                }