btrfs-progs: dump-tree: escape special characters in paths or xattrs

Filenames can contain a newline (or other funny characters), this makes
the dump-tree output confusing, same for xattr names or values that can
binary data.  Encode the special characters in the C-style ('\e' ->
"\e", or \NNN if there's no single letter representation). This is based
on the isprint() as it's espected either on a terminal or in a dump
file.

Issue: #350
Issue: #407
Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

Documentation/btrfs-inspect-internal.rst

@@ -66,8 +66,12 @@ dump-tree [options] <device> [device...]
         a positive educational effect on understanding the internal filesystem structure.
 
         .. note::
-                Contains file names, consider that if you're asked to send the dump for
-                analysis. Does not contain file data.
+                By default contains file names, consider that if you're asked
+                to send the dump for analysis and use *--hide-names* eventually.
+                Does not contain file data.
+
+        Special characters in file names, xattr names and values are escaped,
+        in the C style like ``\n`` and octal encoding ``\NNN``.
 
         ``Options``
 

kernel-shared/print-tree.c

@@ -93,7 +93,9 @@ static void print_dir_item(struct extent_buffer *eb, u32 size,
 		} else {
 			read_extent_buffer(eb, namebuf,
 					(unsigned long)(di + 1), len);
-			printf("\t\tname: %.*s\n", len, namebuf);
+			printf("\t\tname: ");
+			string_print_escape_special_len(namebuf, len);
+			printf("\n");
 		}
 
 		if (data_len) {
@@ -104,7 +106,9 @@ static void print_dir_item(struct extent_buffer *eb, u32 size,
 			} else {
 				read_extent_buffer(eb, namebuf,
 					(unsigned long)(di + 1) + name_len, len);
-				printf("\t\tdata %.*s\n", len, namebuf);
+				printf("\t\tdata ");
+				string_print_escape_special_len(namebuf, len);
+				printf("\n");
 			}
 		}
 		len = sizeof(*di) + name_len + data_len;
@@ -137,7 +141,9 @@ static void print_inode_extref_item(struct extent_buffer *eb, u32 size,
 		} else {
 			read_extent_buffer(eb, namebuf,
 					(unsigned long)extref->name, len);
-			printf("name: %.*s\n", len, namebuf);
+			printf("name: ");
+			string_print_escape_special_len(namebuf, len);
+			printf("\n");
 		}
 
 		len = sizeof(*extref) + name_len;
@@ -167,7 +173,9 @@ static void print_inode_ref_item(struct extent_buffer *eb, u32 size,
 		} else {
 			read_extent_buffer(eb, namebuf,
 					(unsigned long)(ref + 1), len);
-			printf("name: %.*s\n", len, namebuf);
+			printf("name: ");
+			string_print_escape_special_len(namebuf, len);
+			printf("\n");
 		}
 		len = sizeof(*ref) + name_len;
 		ref = (struct btrfs_inode_ref *)((char *)ref + len);