btrfs-progs: mkfs should first check all disks before writing to a disk

In the cases where one of the disk is not suitable for
btrfs, then we would fail the mkfs, however we determine
that after we have written btrfs to the preceding disks.
At this time if user changes mind for not to use btrfs
will left with no choice.

So this patch will check if all the provided disks are
suitable for the btrfs at once before proceeding to
create btrfs on a disk.

Further this patch also removed duplicate code to check
device suitability for the btrfs.

Next, there is an existing bug about the -r mkfs option,
which this patch would carry forward most of it.
Ref:
[PATCH 2/2, RFC] btrfs-progs: overhaul mkfs.btrfs -r option

Signed-off-by: Anand Jain <anand.jain@oracle.com>

to merg prev

Signed-off-by: Anand Jain <anand.jain@oracle.com>

1 files changed, 128 insertions, 0 deletions

diff --git a/utils.c b/utils.c
index fb65b723..412de80c 100644
--- a/utils.c
+++ b/utils.c
@@ -40,6 +40,7 @@
 #include <linux/major.h>
 #include <linux/kdev_t.h>
 #include <limits.h>
+#include <blkid/blkid.h>
 #include "kerncompat.h"
 #include "radix-tree.h"
 #include "ctree.h"
@@ -1679,3 +1680,130 @@ out:
 
 	return ret;
 }
+
+/*
+ * Check for existing filesystem or partition table on device.
+ * Returns:
+ *	 1 for existing fs or partition
+ *	 0 for nothing found
+ *	-1 for internal error
+ */
+static int
+check_overwrite(
+	char		*device)
+{
+	const char	*type;
+	blkid_probe	pr = NULL;
+	int		ret;
+	blkid_loff_t	size;
+
+	if (!device || !*device)
+		return 0;
+
+	ret = -1; /* will reset on success of all setup calls */
+
+	pr = blkid_new_probe_from_filename(device);
+	if (!pr)
+		goto out;
+
+	size = blkid_probe_get_size(pr);
+	if (size < 0)
+		goto out;
+
+	/* nothing to overwrite on a 0-length device */
+	if (size == 0) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = blkid_probe_enable_partitions(pr, 1);
+	if (ret < 0)
+		goto out;
+
+	ret = blkid_do_fullprobe(pr);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * Blkid returns 1 for nothing found and 0 when it finds a signature,
+	 * but we want the exact opposite, so reverse the return value here.
+	 *
+	 * In addition print some useful diagnostics about what actually is
+	 * on the device.
+	 */
+	if (ret) {
+		ret = 0;
+		goto out;
+	}
+
+	if (!blkid_probe_lookup_value(pr, "TYPE", &type, NULL)) {
+		fprintf(stderr,
+			"%s appears to contain an existing "
+			"filesystem (%s).\n", device, type);
+	} else if (!blkid_probe_lookup_value(pr, "PTTYPE", &type, NULL)) {
+		fprintf(stderr,
+			"%s appears to contain a partition "
+			"table (%s).\n", device, type);
+	} else {
+		fprintf(stderr,
+			"%s appears to contain something weird "
+			"according to blkid\n", device);
+	}
+	ret = 1;
+
+out:
+	if (pr)
+		blkid_free_probe(pr);
+	if (ret == -1)
+		fprintf(stderr,
+			"probe of %s failed, cannot detect "
+			  "existing filesystem.\n", device);
+	return ret;
+}
+
+/* Check if disk is suitable for btrfs
+ * returns:
+ *  1: something is wrong, estr provides the error
+ *  0: all is fine
+ */
+int test_dev_for_mkfs(char *file, int force_overwrite, char *estr)
+{
+	int ret, fd;
+	size_t sz = 100;
+
+	ret = is_swap_device(file);
+	if (ret < 0) {
+		snprintf(estr, sz, "error checking %s status: %s\n", file,
+			strerror(-ret));
+		return 1;
+	}
+	if (ret == 1) {
+		snprintf(estr, sz, "%s is a swap device\n", file);
+		return 1;
+	}
+	if (!force_overwrite) {
+		if (check_overwrite(file)) {
+			snprintf(estr, sz, "Use the -f option to force overwrite.\n");
+			return 1;
+		}
+	}
+	ret = check_mounted(file);
+	if (ret < 0) {
+		snprintf(estr, sz, "error checking %s mount status\n",
+			file);
+		return 1;
+	}
+	if (ret == 1) {
+		snprintf(estr, sz, "%s is mounted\n", file);
+		return 1;
+	}
+	/* check if the device is busy */
+	fd = open(file, O_RDWR|O_EXCL);
+	if (fd < 0) {
+		snprintf(estr, sz, "unable to open %s: %s\n", file,
+			strerror(errno));
+		return 1;
+	}
+	close(fd);
+	return 0;
+}