[PATCH 3/3] mke2fs: check for a partition table and warn if present

["Theodore Ts'o" <tytso@xxxxxxx>]

This supercedes the "whole disk" check, since it does a better job and
there are times when it is quite legitimate to want to use the whole
disk.

Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
 configure       |  2 +-
 configure.in    |  1 +
 lib/config.h.in |  3 +++
 misc/util.c     | 48 +++++++++++++++++++++++++++++++++++++++++-------
 4 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/configure b/configure
index 44664c3..6fe33f5 100755
--- a/configure
+++ b/configure
@@ -11078,7 +11078,7 @@ if test "$ac_res" != no; then :
 fi
 
 fi
-for ac_func in  	__secure_getenv 	backtrace 	blkid_probe_get_topology 	chflags 	fadvise64 	fallocate 	fallocate64 	fchown 	fdatasync 	fstat64 	ftruncate64 	futimes 	getcwd 	getdtablesize 	getmntinfo 	getpwuid_r 	getrlimit 	getrusage 	jrand48 	llseek 	lseek64 	mallinfo 	mbstowcs 	memalign 	mempcpy 	mmap 	msync 	nanosleep 	open64 	pathconf 	posix_fadvise 	posix_fadvise64 	posix_memalign 	prctl 	secure_getenv 	setmntent 	setresgid 	setresuid 	srandom 	stpcpy 	strcasecmp 	strdup 	strnlen 	strptime 	strtoull 	sync_file_range 	sysconf 	usleep 	utime 	valloc
+for ac_func in  	__secure_getenv 	backtrace 	blkid_probe_get_topology 	blkid_probe_enable_partitions 	chflags 	fadvise64 	fallocate 	fallocate64 	fchown 	fdatasync 	fstat64 	ftruncate64 	futimes 	getcwd 	getdtablesize 	getmntinfo 	getpwuid_r 	getrlimit 	getrusage 	jrand48 	llseek 	lseek64 	mallinfo 	mbstowcs 	memalign 	mempcpy 	mmap 	msync 	nanosleep 	open64 	pathconf 	posix_fadvise 	posix_fadvise64 	posix_memalign 	prctl 	secure_getenv 	setmntent 	setresgid 	setresuid 	srandom 	stpcpy 	strcasecmp 	strdup 	strnlen 	strptime 	strtoull 	sync_file_range 	sysconf 	usleep 	utime 	valloc
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
diff --git a/configure.in b/configure.in
index e0e6d48..781b6f5 100644
--- a/configure.in
+++ b/configure.in
@@ -1050,6 +1050,7 @@ AC_CHECK_FUNCS(m4_flatten([
 	__secure_getenv
 	backtrace
 	blkid_probe_get_topology
+	blkid_probe_enable_partitions
 	chflags
 	fadvise64
 	fallocate
diff --git a/lib/config.h.in b/lib/config.h.in
index b575a5c..92b3c49 100644
--- a/lib/config.h.in
+++ b/lib/config.h.in
@@ -55,6 +55,9 @@
 /* Define to 1 if you have the `backtrace' function. */
 #undef HAVE_BACKTRACE
 
+/* Define to 1 if you have the `blkid_probe_enable_partitions' function. */
+#undef HAVE_BLKID_PROBE_ENABLE_PARTITIONS
+
 /* Define to 1 if you have the `blkid_probe_get_topology' function. */
 #undef HAVE_BLKID_PROBE_GET_TOPOLOGY
 
diff --git a/misc/util.c b/misc/util.c
index d63e21b..d0e4c7e 100644
--- a/misc/util.c
+++ b/misc/util.c
@@ -139,13 +139,50 @@ static void print_ext2_info(const char *device)
 	ext2fs_close(fs);
 }
 
+/*
+ * return 1 if there is no partition table, 0 if a partition table is
+ * detected, and -1 on an error.
+ */
+static int check_partition_table(const char *device)
+{
+#ifdef HAVE_BLKID_PROBE_ENABLE_PARTITIONS
+	blkid_probe pr;
+	const char *value;
+	int ret;
+
+	pr = blkid_new_probe_from_filename(device);
+	if (!pr)
+		return -1;
+
+        ret = blkid_probe_enable_partitions(pr, 1);
+        if (ret < 0)
+		goto errout;
+
+	ret = blkid_do_fullprobe(pr);
+	if (ret < 0)
+		goto errout;
+
+	ret = blkid_probe_lookup_value(pr, "PTTYPE", &value, NULL);
+	if (ret == 0)
+		fprintf(stderr, _("Found a %s partition table in %s\n"),
+			value, device);
+	else
+		ret = 1;
+
+errout:
+	blkid_free_probe(pr);
+	return ret;
+#else
+	return -1;
+#endif
+}
 
 /*
  * return 1 if the device looks plausible, creating the file if necessary
  */
 int check_plausibility(const char *device, int flags, int *ret_is_dev)
 {
-	int fd, is_dev = 0;
+	int fd, ret, is_dev = 0;
 	ext2fs_struct_stat s;
 	int fl = O_RDONLY;
 	blkid_cache cache = NULL;
@@ -210,12 +247,9 @@ int check_plausibility(const char *device, int flags, int *ret_is_dev)
 		return 0;
 	}
 
-	/*
-	 * We should eventually replace this with a test for the
-	 * presence of a partition table.  Unfortunately the blkid
-	 * library doesn't test for partition tabels, and checking for
-	 * valid GPT and MBR and possibly others isn't quite trivial.
-	 */
+	ret = check_partition_table(device);
+	if (ret >= 0)
+		return ret;
 
 #ifdef HAVE_LINUX_MAJOR_H
 #ifndef MAJOR
-- 
1.9.0

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