generic: Check the stx_attributes settable by chattr

Check the stx_attributes that can be set by calling chattr.

The script probes the filesystem with chattr to find out which of
+a, +c, +d and +i are supported before testing combinations of
attrs.  Note that if a filesystem supports chattr with these, but
doesn't paste the flag values into stx_attributes, the test will
fail as there's no way to distinguish cleared from unset.

Certain chattr flags are reflected in specific stx_attributes flags:

	chattr flag	stx_attributes flag
	+a		STATX_ATTR_APPEND
	+c		STATX_ATTR_COMPRESSED
	+d		STATX_ATTR_NODUMP
	+i		STATX_ATTR_IMMUTABLE

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

doc/requirement-checking.txt

@@ -12,7 +12,11 @@ they have.  This is done with _require_<xxx> macros, which may take parameters.
 	_require_test_program <name>
 	_require_xfs_io_command <name> [<switch>]
 
- (2) System call requirements.
+ (2) Filesystem capability requirements.
+
+	_require_chattr <letters>
+
+ (3) System call requirements.
 
 	_require_statx
 
@@ -67,6 +71,22 @@ _require_xfs_io_command <name> [<switch>]
      the +x and -x arguments (DAX attribute).
 
 
+==================================
+FILESYSTEM CAPABILITY REQUIREMENTS
+==================================
+
+_require_chattr <letters>
+
+     The test requires that the filesystem attribute set by the chattr command
+     with +<letters> as an argument be available and supported by the $TEST_DEV
+     filesystem.  No check is made of the scratch filesystem.  For example:
+
+	_require_chattr ai
+
+     tests to see if setting the append-only and immutable attributes on a file
+     (chattr +a +i) is supported.
+
+
 ========================
 SYSTEM CALL REQUIREMENTS
 ========================