Add autotools support for BtrFS option

Feature is enabled by default, if headers are available. It can be
turned off explictly.

configure.ac

@@ -253,6 +253,9 @@ AC_ARG_WITH(audit,
 AC_ARG_WITH(libpam,
 	[AC_HELP_STRING([--with-libpam], [use libpam for PAM support @<:@default=yes if found@:>@])],
 	[with_libpam=$withval], [with_libpam=maybe])
+AC_ARG_WITH(btrfs,
+	[AC_HELP_STRING([--with-btrfs], [add BtrFS support @<:@default=yes if found@:>@])],
+	[with_selinux=$withval], [with_selinux=maybe])
 AC_ARG_WITH(selinux,
 	[AC_HELP_STRING([--with-selinux], [use SELinux support @<:@default=yes if found@:>@])],
 	[with_selinux=$withval], [with_selinux=maybe])
@@ -459,6 +462,20 @@ if test "$with_libcrack" = "yes"; then
 		AC_DEFINE(HAVE_LIBCRACK_PW, 1, [Defined if it includes *Pw functions.]))
 fi
 
+if test "$with_btrfs" != "no"; then
+	AC_CHECK_HEADERS([sys/statfs.h linux/magic.h linux/btrfs_tree.h], \
+		[btrfs_headers="yes"], [btrfs_headers="no"])
+	if test "$btrfs_headers$with_btrfs" = "noyes" ; then
+		AC_MSG_ERROR([One of sys/statfs.h linux/magic.h linux/btrfs_tree.h is missing])
+	fi
+
+	if test "$btrfs_headers" = "yes" ; then
+		AC_DEFINE(WITH_BTRFS, 1, [Build shadow with BtrFS support])
+		with_btrfs="yes"
+	fi
+fi
+AM_CONDITIONAL(WITH_BTRFS, test x$with_btrfs = xyes)
+
 AC_SUBST(LIBSELINUX)
 AC_SUBST(LIBSEMANAGE)
 if test "$with_selinux" != "no"; then
@@ -691,6 +708,7 @@ if test "$with_libpam" = "yes"; then
 echo "	suid account management tools:	$enable_acct_tools_setuid"
 fi
 echo "	SELinux support:		$with_selinux"
+echo "	BtrFS support:			$with_btrfs"
 echo "	ACL support:			$with_acl"
 echo "	Extended Attributes support:	$with_attr"
 echo "	tcb support (incomplete):	$with_tcb"

lib/prototypes.h

@@ -73,10 +73,12 @@ extern int expire (const struct passwd *, /*@null@*/const struct spwd *);
 extern int isexpired (const struct passwd *, /*@null@*/const struct spwd *);
 
 /* btrfs.c */
+#ifdef WITH_BTRFS
 extern int btrfs_create_subvolume(const char *path);
 extern int btrfs_remove_subvolume(const char *path);
 extern int btrfs_is_subvolume(const char *path);
 extern int is_btrfs(const char *path);
+#endif
 
 /* basename() renamed to Basename() to avoid libc name space confusion */
 /* basename.c */

libmisc/Makefile.am

@@ -10,7 +10,6 @@ libmisc_a_SOURCES = \
 	age.c \
 	audit_help.c \
 	basename.c \
-	btrfs.c \
 	chkname.c \
 	chkname.h \
 	chowndir.c \
@@ -73,3 +72,8 @@ libmisc_a_SOURCES = \
 	xgetspnam.c \
 	xmalloc.c \
 	yesno.c
+
+if WITH_BTRFS
+libmisc_a_SOURCES += btrfs.c
+endif
+

src/useradd.c

@@ -823,7 +823,9 @@ static void usage (int status)
 	                Prog, Prog, Prog);
 	(void) fputs (_("  -b, --base-dir BASE_DIR       base directory for the home directory of the\n"
 	                "                                new account\n"), usageout);
+#ifdef WITH_BTRFS
 	(void) fputs (_("      --btrfs-subvolume-home    use BTRFS subvolume for home directory\n"), usageout);
+#endif
 	(void) fputs (_("  -c, --comment COMMENT         GECOS field of the new account\n"), usageout);
 	(void) fputs (_("  -d, --home-dir HOME_DIR       home directory of the new account\n"), usageout);
 	(void) fputs (_("  -D, --defaults                print or change default useradd configuration\n"), usageout);
@@ -1104,7 +1106,9 @@ static void process_flags (int argc, char **argv)
 		int c;
 		static struct option long_options[] = {
 			{"base-dir",       required_argument, NULL, 'b'},
+#ifdef WITH_BTRFS
 			{"btrfs-subvolume-home", no_argument, NULL, 200},
+#endif
 			{"comment",        required_argument, NULL, 'c'},
 			{"home-dir",       required_argument, NULL, 'd'},
 			{"defaults",       no_argument,       NULL, 'D'},
@@ -2083,6 +2087,7 @@ static void create_home (void)
 				   subvolume but no BTRFS. The paths cound be different by the
 				   trailing slash
 				 */
+#if WITH_BTRFS
 				if (subvolflg && (strlen(prefix_user_home) - (int)strlen(path)) <= 1) {
 					char *btrfs_check = strdup(path);
 
@@ -2107,7 +2112,9 @@ static void create_home (void)
 						fail_exit (E_HOMEDIR);
 					}
 				}
-				else if (mkdir (path, 0) != 0) {
+				else
+#endif
+				if (mkdir (path, 0) != 0) {
 			fprintf (stderr,
 							_("%s: cannot create directory %s\n"),
 							Prog, path);

src/userdel.c

@@ -1272,6 +1272,7 @@ int main (int argc, char **argv)
 #endif				/* EXTRA_CHECK_HOME_DIR */
 
 	if (rflg) {
+#ifdef WITH_BTRFS
 		int is_subvolume = btrfs_is_subvolume (user_home);
 		if (is_subvolume < 0) {
 		    errors++;
@@ -1286,7 +1287,9 @@ int main (int argc, char **argv)
 				/* continue */
 			}
 		}
-		else if (remove_tree (user_home, true) != 0) {
+		else
+#endif
+		if (remove_tree (user_home, true) != 0) {
 			fprintf (stderr,
 			         _("%s: error removing directory %s\n"),
 			         Prog, user_home);

src/usermod.c

@@ -1819,12 +1819,14 @@ static void move_home (void)
 			return;
 		} else {
 			if (EXDEV == errno) {
+#ifdef WITH_BTRFS
 				if (btrfs_is_subvolume (prefix_user_home) > 0) {
 					fprintf (stderr,
 					        _("%s: error: cannot move subvolume from %s to %s - different device\n"),
 					        Prog, prefix_user_home, prefix_user_newhome);
 					fail_exit (E_HOMEDIR);
 				}
+#endif
 
 				if (copy_tree (prefix_user_home, prefix_user_newhome, true,
 				               true,