btrfs: rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE

The name BTRFS_ROOT_REF_COWS is not very clear about the meaning.

In fact, that bit can only be set to those trees:

- Subvolume roots
- Data reloc root
- Reloc roots for above roots

All other trees won't get this bit set.  So just by the result, it is
obvious that, roots with this bit set can have tree blocks shared with
other trees.  Either shared by snapshots, or by reloc roots (an special
snapshot created by relocation).

This patch will rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE to
make it easier to understand, and update all comment mentioning
"reference counted" to follow the rename.

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

1 files changed, 9 insertions, 8 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3ea694ee1c90..08c02bd148a6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4100,11 +4100,12 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 	BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);
 
 	/*
-	 * for non-free space inodes and ref cows, we want to back off from
-	 * time to time
+	 * For non-free space inodes and non-shareable roots, we want to back
+	 * off from time to time.  This means all inodes in subvolume roots,
+	 * reloc roots, and data reloc roots.
 	 */
 	if (!btrfs_is_free_space_inode(BTRFS_I(inode)) &&
-	    test_bit(BTRFS_ROOT_REF_COWS, &root->state))
+	    test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
 		be_nice = true;
 
 	path = btrfs_alloc_path();
@@ -4121,7 +4122,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 	 * not block aligned since we will be keeping the last block of the
 	 * extent just the way it is.
 	 */
-	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
+	if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
 	    root == fs_info->tree_root)
 		btrfs_drop_extent_cache(BTRFS_I(inode), ALIGN(new_size,
 					fs_info->sectorsize),
@@ -4233,7 +4234,7 @@ search_again:
 							 extent_num_bytes);
 				num_dec = (orig_num_bytes -
 					   extent_num_bytes);
-				if (test_bit(BTRFS_ROOT_REF_COWS,
+				if (test_bit(BTRFS_ROOT_SHAREABLE,
 					     &root->state) &&
 				    extent_start != 0)
 					inode_sub_bytes(inode, num_dec);
@@ -4249,7 +4250,7 @@ search_again:
 				num_dec = btrfs_file_extent_num_bytes(leaf, fi);
 				if (extent_start != 0) {
 					found_extent = 1;
-					if (test_bit(BTRFS_ROOT_REF_COWS,
+					if (test_bit(BTRFS_ROOT_SHAREABLE,
 						     &root->state))
 						inode_sub_bytes(inode, num_dec);
 				}
@@ -4285,7 +4286,7 @@ search_again:
 				clear_len = fs_info->sectorsize;
 			}
 
-			if (test_bit(BTRFS_ROOT_REF_COWS, &root->state))
+			if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
 				inode_sub_bytes(inode, item_end + 1 - new_size);
 		}
 delete:
@@ -4326,7 +4327,7 @@ delete:
 		should_throttle = false;
 
 		if (found_extent &&
-		    (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
+		    (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
 		     root == fs_info->tree_root)) {
 			struct btrfs_ref ref = { 0 };