btrfs-progs: fi du: don't call lookup_path_rootid for BTRFS_EMPTY_SUBVOL_DIR_OBJECTID

When ino is BTRFS_EMPTY_SUBVOL_DIR_OBJECTID, the item is not referred to
any file-tree. So lookup_path_rootid() doesn't return any meaningful
value.

As was reported, this can be triggered by

$ btrfs sub create test1
$ btrfs sub create test1/test2
$ btrfs sub snap test1 test1.snap
$ btrfs fi du -s test1
  Total   Exclusive  Set shared  Filename
  0.00B       0.00B       0.00B  test1
$ btrfs fi du -s test1.snap
  Total   Exclusive  Set shared  Filename
ERROR: cannot check space of 'test1.snap': Inappropriate ioctl for device

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Signed-off-by: David Sterba <dsterba@suse.com>

2 files changed, 18 insertions, 9 deletions

diff --git a/cmds-fi-du.c b/cmds-fi-du.c
index 4bf6af3e..8a44665c 100644
--- a/cmds-fi-du.c
+++ b/cmds-fi-du.c
@@ -433,7 +433,6 @@ static int du_add_file(const char *filename, int dirfd,
 	u64 file_total = 0;
 	u64 file_shared = 0;
 	u64 dir_set_shared = 0;
-	u64 subvol;
 	int fd;
 	DIR *dirstream = NULL;
 
@@ -462,16 +461,24 @@ static int du_add_file(const char *filename, int dirfd,
 		goto out;
 	}
 
-	ret = lookup_path_rootid(fd, &subvol);
-	if (ret)
-		goto out_close;
+	/*
+	 * If st.st_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID ==2, there is no any
+	 * related tree
+	 */
+	if (st.st_ino != BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
+		u64 subvol;
 
-	if (inode_seen(st.st_ino, subvol))
-		goto out_close;
+		ret = lookup_path_rootid(fd, &subvol);
+		if (ret)
+			goto out_close;
 
-	ret = mark_inode_seen(st.st_ino, subvol);
-	if (ret)
-		goto out_close;
+		if (inode_seen(st.st_ino, subvol))
+			goto out_close;
+
+		ret = mark_inode_seen(st.st_ino, subvol);
+		if (ret)
+			goto out_close;
+	}
 
 	if (S_ISREG(st.st_mode)) {
 		ret = du_calc_file_space(fd, shared_extents, &file_total,
diff --git a/ctree.h b/ctree.h
index 2818441f..81c193f1 100644
--- a/ctree.h
+++ b/ctree.h
@@ -138,6 +138,8 @@ struct btrfs_free_space_ctl;
  */
 #define BTRFS_DEV_ITEMS_OBJECTID 1ULL
 
+#define BTRFS_EMPTY_SUBVOL_DIR_OBJECTID 2ULL
+
 /*
  * the max metadata block size.  This limit is somewhat artificial,
  * but the memmove costs go through the roof for larger blocks.