btrfs: use a single argument for extent offset in backref walking functions

The interface for find_parent_nodes() has two extent offset related
arguments:

1) One u64 pointer argument for the extent offset;

2) One boolean argument to tell if the extent offset should be ignored or
   not.

These are confusing, becase the extent offset pointer can be NULL and in
some cases callers pass a NULL value as a way to tell the backref walking
code to ignore offsets in file extent items (and simply consider all file
extent items that point to the target data extent).

The boolean argument was added in commit c995ab3c ("btrfs: add a flag
to iterate_inodes_from_logical to find all extent refs for uncompressed
extents"), but it was never really necessary, it was enough if it could
find a way to get a NULL value passed to the "extent_item_pos" argument of
find_parent_nodes(). The arguments are also passed to functions called
by find_parent_nodes() and respective helper functions, which further
makes everything more complicated than needed.

Then we have several backref walking related functions that end up calling
find_parent_nodes(), either directly or through some other function that
they call, and for many we have to use an "extent_item_pos" (u64) argument
and a boolean "ignore_offset" argument too.

This is confusing and not really necessary. So use a single argument to
specify the extent offset, as a simple u64 and not as a pointer, but
using a special value of (u64)-1, defined as a documented constant, to
indicate when the extent offset should be ignored.

This is also preparation work for the upcoming patches in the series that
add other arguments to find_parent_nodes() and other related functions
that use it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/backref.h

@@ -12,6 +12,13 @@
 #include "disk-io.h"
 #include "extent_io.h"
 
+/*
+ * Pass to backref walking functions to tell them to include references from
+ * all file extent items that point to the target data extent, regardless if
+ * they refer to the whole extent or just sections of it (bookend extents).
+ */
+#define BTRFS_IGNORE_EXTENT_OFFSET   ((u64)-1)
+
 struct inode_fs_paths {
 	struct btrfs_path		*btrfs_path;
 	struct btrfs_root		*fs_root;
@@ -92,8 +99,7 @@ int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
 				u64 extent_item_objectid,
 				u64 extent_offset, int search_commit_root,
-				iterate_extent_inodes_t *iterate, void *ctx,
-				bool ignore_offset);
+				iterate_extent_inodes_t *iterate, void *ctx);
 
 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
 				struct btrfs_path *path, void *ctx,
@@ -104,7 +110,7 @@ int paths_from_inode(u64 inum, struct inode_fs_paths *ipath);
 int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
 			 struct btrfs_fs_info *fs_info, u64 bytenr,
 			 u64 time_seq, struct ulist **leafs,
-			 const u64 *extent_item_pos, bool ignore_offset);
+			 u64 extent_item_pos);
 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
 			 struct btrfs_fs_info *fs_info, u64 bytenr,
 			 u64 time_seq, struct ulist **roots,

fs/btrfs/relocation.c

@@ -3417,7 +3417,7 @@ int add_data_references(struct reloc_control *rc,
 
 	btrfs_release_path(path);
 	ret = btrfs_find_all_leafs(NULL, fs_info, extent_key->objectid,
-				   0, &leaves, NULL, true);
+				   0, &leaves, BTRFS_IGNORE_EXTENT_OFFSET);
 	if (ret < 0)
 		return ret;
 

fs/btrfs/scrub.c

@@ -969,7 +969,7 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 		swarn.dev = dev;
 		iterate_extent_inodes(fs_info, found_key.objectid,
 					extent_item_pos, 1,
-					scrub_print_warning_inode, &swarn, false);
+					scrub_print_warning_inode, &swarn);
 	}
 
 out:

fs/btrfs/send.c

@@ -1467,7 +1467,7 @@ static int find_extent_clone(struct send_ctx *sctx,
 		extent_item_pos = 0;
 	ret = iterate_extent_inodes(fs_info, found_key.objectid,
 				    extent_item_pos, 1, __iterate_backrefs,
-				    &backref_ctx, false);
+				    &backref_ctx);
 
 	if (ret < 0)
 		goto out;