btrfs: add dedicated members for start and length of a block group

The on-disk format of block group item makes use of the key that stores
the offset and length. This is further used in the code, although this
makes thing harder to understand. The key is also packed so the
offset/length is not properly aligned as u64.

Add start (key.objectid) and length (key.offset) members to block group
and remove the embedded key.  When the item is searched or written, a
local variable for key is used.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 18 insertions, 19 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index e4ea277d4e01..279c41c4ba50 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -107,7 +107,7 @@ struct inode *lookup_free_space_inode(
 		return inode;
 
 	inode = __lookup_free_space_inode(fs_info->tree_root, path,
-					  block_group->key.objectid);
+					  block_group->start);
 	if (IS_ERR(inode))
 		return inode;
 
@@ -201,7 +201,7 @@ int create_free_space_inode(struct btrfs_trans_handle *trans,
 		return ret;
 
 	return __create_free_space_inode(trans->fs_info->tree_root, trans, path,
-					 ino, block_group->key.objectid);
+					 ino, block_group->start);
 }
 
 int btrfs_check_trunc_cache_free_space(struct btrfs_fs_info *fs_info,
@@ -882,13 +882,13 @@ int load_free_space_cache(struct btrfs_block_group_cache *block_group)
 	spin_unlock(&block_group->lock);
 
 	ret = __load_free_space_cache(fs_info->tree_root, inode, ctl,
-				      path, block_group->key.objectid);
+				      path, block_group->start);
 	btrfs_free_path(path);
 	if (ret <= 0)
 		goto out;
 
 	spin_lock(&ctl->tree_lock);
-	matched = (ctl->free_space == (block_group->key.offset - used -
+	matched = (ctl->free_space == (block_group->length - used -
 				       block_group->bytes_super));
 	spin_unlock(&ctl->tree_lock);
 
@@ -896,7 +896,7 @@ int load_free_space_cache(struct btrfs_block_group_cache *block_group)
 		__btrfs_remove_free_space_cache(ctl);
 		btrfs_warn(fs_info,
 			   "block group %llu has wrong amount of free space",
-			   block_group->key.objectid);
+			   block_group->start);
 		ret = -1;
 	}
 out:
@@ -909,7 +909,7 @@ out:
 
 		btrfs_warn(fs_info,
 			   "failed to load free space cache for block group %llu, rebuilding it now",
-			   block_group->key.objectid);
+			   block_group->start);
 	}
 
 	iput(inode);
@@ -1067,9 +1067,9 @@ static noinline_for_stack int write_pinned_extent_entries(
 	 */
 	unpin = block_group->fs_info->pinned_extents;
 
-	start = block_group->key.objectid;
+	start = block_group->start;
 
-	while (start < block_group->key.objectid + block_group->key.offset) {
+	while (start < block_group->start + block_group->length) {
 		ret = find_first_extent_bit(unpin, start,
 					    &extent_start, &extent_end,
 					    EXTENT_DIRTY, NULL);
@@ -1077,13 +1077,12 @@ static noinline_for_stack int write_pinned_extent_entries(
 			return 0;
 
 		/* This pinned extent is out of our range */
-		if (extent_start >= block_group->key.objectid +
-		    block_group->key.offset)
+		if (extent_start >= block_group->start + block_group->length)
 			return 0;
 
 		extent_start = max(extent_start, start);
-		extent_end = min(block_group->key.objectid +
-				 block_group->key.offset, extent_end + 1);
+		extent_end = min(block_group->start + block_group->length,
+				 extent_end + 1);
 		len = extent_end - extent_start;
 
 		*entries += 1;
@@ -1174,7 +1173,7 @@ out:
 #ifdef DEBUG
 			btrfs_err(root->fs_info,
 				  "failed to write free space cache for block group %llu",
-				  block_group->key.objectid);
+				  block_group->start);
 #endif
 		}
 	}
@@ -1221,7 +1220,7 @@ int btrfs_wait_cache_io(struct btrfs_trans_handle *trans,
 {
 	return __btrfs_wait_cache_io(block_group->fs_info->tree_root, trans,
 				     block_group, &block_group->io_ctl,
-				     path, block_group->key.objectid);
+				     path, block_group->start);
 }
 
 /**
@@ -1400,7 +1399,7 @@ int btrfs_write_out_cache(struct btrfs_trans_handle *trans,
 #ifdef DEBUG
 		btrfs_err(fs_info,
 			  "failed to write free space cache for block group %llu",
-			  block_group->key.objectid);
+			  block_group->start);
 #endif
 		spin_lock(&block_group->lock);
 		block_group->disk_cache_state = BTRFS_DC_ERROR;
@@ -1657,7 +1656,7 @@ static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
 	u64 max_bytes;
 	u64 bitmap_bytes;
 	u64 extent_bytes;
-	u64 size = block_group->key.offset;
+	u64 size = block_group->length;
 	u64 bytes_per_bg = BITS_PER_BITMAP * ctl->unit;
 	u64 max_bitmaps = div64_u64(size + bytes_per_bg - 1, bytes_per_bg);
 
@@ -2034,7 +2033,7 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 	 * so allow those block groups to still be allowed to have a bitmap
 	 * entry.
 	 */
-	if (((BITS_PER_BITMAP * ctl->unit) >> 1) > block_group->key.offset)
+	if (((BITS_PER_BITMAP * ctl->unit) >> 1) > block_group->length)
 		return false;
 
 	return true;
@@ -2516,7 +2515,7 @@ void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group)
 
 	spin_lock_init(&ctl->tree_lock);
 	ctl->unit = fs_info->sectorsize;
-	ctl->start = block_group->key.objectid;
+	ctl->start = block_group->start;
 	ctl->private = block_group;
 	ctl->op = &free_space_op;
 	INIT_LIST_HEAD(&ctl->trimming_ranges);
@@ -3379,7 +3378,7 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group_cache *block_group)
 		mutex_lock(&fs_info->chunk_mutex);
 		em_tree = &fs_info->mapping_tree;
 		write_lock(&em_tree->lock);
-		em = lookup_extent_mapping(em_tree, block_group->key.objectid,
+		em = lookup_extent_mapping(em_tree, block_group->start,
 					   1);
 		BUG_ON(!em); /* logic error, can't happen */
 		remove_extent_mapping(em_tree, em);