Re: [patch 1/1] [mdadm] Add partition checks when creating a new array

[Neil Brown <neilb@suse.de>]

On Thu, 19 Nov 2009 15:40:21 +0000
"Trela, Maciej" <Maciej.Trela@intel.com> wrote:

> Hello Neil,
> I made some research but unfortunately I couldn't find any other library except libparted.
> Assuming there are no other possibilities, do you think we could stay with the current solution or should I switch the patch to libparted?
> 
> I have the impression that with libparted this simple patch would be much bigger (given the code size)...
> 


Fair enough.

I have made some changes resulting in the following patch.

Thanks,
NeilBrown

From 034b203a4754da7615d7b16bafeabfc4115dabea Mon Sep 17 00:00:00 2001
From: Trela, Maciej <Maciej.Trela@intel.com>
Date: Tue, 8 Dec 2009 16:07:47 +1100
Subject: [PATCH] Check partition tables when creating array.

When creating an array, check if the devices have partition
tables and print a warning if the table or the partitions might be
destroyed by array creation.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 Create.c |   17 +++++-
 mdadm.h  |    1 +
 util.c   |  176 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 191 insertions(+), 3 deletions(-)

diff --git a/Create.c b/Create.c
index 5b01b63..d104c05 100644
--- a/Create.c
+++ b/Create.c
@@ -375,11 +375,22 @@ int Create(struct supertype *st, char *mddev,
 			warn |= check_ext2(fd, dname);
 			warn |= check_reiser(fd, dname);
 			warn |= check_raid(fd, dname);
-			if (st && strcmp(st->ss->name, "1.x") == 0 &&
+			if (strcmp(st->ss->name, "1.x") == 0 &&
+			    st->minor_version >= 1)
+				/* metadata at front */
+				warn |= check_partitions(fd, dname, 0);
+			else if (level == 1 || level == LEVEL_CONTAINER)
+				/* partitions could be meaningful */
+				warn |= check_partitions(fd, dname, freesize*2);
+			else
+				/* partitions cannot be meaningful */
+				warn |= check_partitions(fd, dname, 0);
+			if (strcmp(st->ss->name, "1.x") == 0 &&
 			    st->minor_version >= 1 &&
 			    did_default &&
-			    level == 1) {
-				warn = 1;
+			    level == 1 &&
+			    (warn & 1024) == 0) {
+				warn |= 1024;
 				fprintf(stderr, Name ": Note: this array has metadata at the start and\n"
 					"    may not be suitable as a boot device.  If you plan to\n"
 					"    store '/' or '/boot' on this device please ensure that\n"
diff --git a/mdadm.h b/mdadm.h
index c7f864b..2bfe840 100644
--- a/mdadm.h
+++ b/mdadm.h
@@ -787,6 +787,7 @@ extern int parse_layout_faulty(char *layout);
 extern int check_ext2(int fd, char *name);
 extern int check_reiser(int fd, char *name);
 extern int check_raid(int fd, char *name);
+extern int check_partitions(int fd, char *dname, unsigned long long freesize);
 
 extern int get_mdp_major(void);
 extern int dev_open(char *dev, int flags);
diff --git a/util.c b/util.c
index a0e4bcf..67c3550 100644
--- a/util.c
+++ b/util.c
@@ -65,6 +65,43 @@ struct blkpg_partition {
 	char volname[BLKPG_VOLNAMELTH];	/* volume label */
 };
 
+/* partition table structures so we can check metadata position
+ * against the end of the last partition.
+ * Only handle MBR ant GPT partition tables.
+ */
+struct MBR_part_record {
+  __u8 bootable;
+  __u8 first_head;
+  __u8 first_sector;
+  __u8 first_cyl;
+  __u8 part_type;
+  __u8 last_head;
+  __u8 last_sector;
+  __u8 last_cyl;
+  __u32 first_sect_lba;
+  __u32 blocks_num;
+};
+
+struct GPT_part_entry {
+  unsigned char type_guid[16];
+  unsigned char partition_guid[16];
+  unsigned char starting_lba[8];
+  unsigned char ending_lba[8];
+  unsigned char attr_bits[8];
+  unsigned char name[72];
+};
+
+/* MBR/GPT magic numbers */
+#define	MBR_SIGNATURE_MAGIC	__cpu_to_le16(0xAA55)
+#define	GPT_SIGNATURE_MAGIC	__cpu_to_le64(0x5452415020494645ULL)
+
+#define MBR_SIGNATURE_OFFSET         510
+#define MBR_PARTITION_TABLE_OFFSET   446
+#define MBR_PARTITIONS               4
+#define MBR_GPT_PARTITION_TYPE       0xEE
+#define GPT_ALL_PARTITIONS_OFFSET    80
+#define GPT_ENTRY_SIZE_OFFSET        84
+
 /*
  * Parse a 128 bit uuid in 4 integers
  * format is 32 hexx nibbles with options :.<space> separator
@@ -1096,6 +1133,145 @@ int get_dev_size(int fd, char *dname, unsigned long long *sizep)
 	return 1;
 }
 
+
+/* Sets endofpart parameter to the last block used by the last GPT partition on the device.
+ * Returns: 1 if successful
+ *         -1 for unknown partition type
+ *          0 for other errors
+ */
+static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
+{
+	unsigned char buf[512];
+	unsigned char empty_gpt_entry[16]= {0};
+	struct GPT_part_entry *part;
+	unsigned long long curr_part_end;
+	unsigned all_partitions, entry_size;
+	int part_nr;
+
+	*endofpart = 0;
+
+	/* read GPT header */
+	lseek(fd, 512, SEEK_SET);
+	if (read(fd, buf, 512) != 512)
+		return 0;
+
+	/* get the number of partition entries and the entry size */
+	all_partitions = __le32_to_cpu(buf[GPT_ALL_PARTITIONS_OFFSET]);
+	entry_size = __le32_to_cpu(buf[GPT_ENTRY_SIZE_OFFSET]);
+
+	/* Check GPT signature*/
+	if (*((__u64*)buf) != GPT_SIGNATURE_MAGIC)
+		return -1;
+
+	/* sanity checks */
+	if (all_partitions > 1024 ||
+	    entry_size > 512)
+		return -1;
+
+	/* read first GPT partition entries */
+	if (read(fd, buf, 512) != 512)
+		return 0;
+
+	part = (struct GPT_part_entry*)buf;
+
+	for (part_nr=0; part_nr < all_partitions; part_nr++) {
+		/* is this valid partition? */
+		if (memcmp(part->type_guid, empty_gpt_entry, 16) != 0) {
+			/* check the last lba for the current partition */
+			curr_part_end = __le64_to_cpu(*(__u64*)part->ending_lba);
+			if (curr_part_end > *endofpart)
+				*endofpart = curr_part_end;
+		}
+
+		part = (struct GPT_part_entry*)((unsigned char*)part + entry_size);
+
+		if ((unsigned char *)part >= buf + 512) {
+			if (read(fd, buf, 512) != 512)
+				return 0;
+			part = (struct GPT_part_entry*)buf;
+		}
+	}
+	return 1;
+}
+
+/* Sets endofpart parameter to the last block used by the last partition on the device.
+ * Returns: 1 if successful
+ *         -1 for unknown partition type
+ *          0 for other errors
+ */
+static int get_last_partition_end(int fd, unsigned long long *endofpart)
+{
+	unsigned char boot_sect[512];
+	struct MBR_part_record *part;
+	unsigned long long curr_part_end;
+	int part_nr;
+	int retval = 0;
+
+	*endofpart = 0;
+
+	/* read MBR */
+	lseek(fd, 0, 0);
+	if (read(fd, boot_sect, 512) != 512)
+		goto abort;
+
+	/* check MBP signature */
+	if (*((__u16*)(boot_sect + MBR_SIGNATURE_OFFSET))
+	    == MBR_SIGNATURE_MAGIC) {
+		retval = 1;
+		/* found the correct signature */
+		part = (struct MBR_part_record*)
+			(boot_sect + MBR_PARTITION_TABLE_OFFSET);
+
+		for (part_nr=0; part_nr < MBR_PARTITIONS; part_nr++) {
+			/* check for GPT type */
+			if (part->part_type == MBR_GPT_PARTITION_TYPE) {
+				retval = get_gpt_last_partition_end(fd, endofpart);
+				break;
+			}
+			/* check the last used lba for the current partition  */
+			curr_part_end = __le32_to_cpu(part->first_sect_lba) +
+				__le32_to_cpu(part->blocks_num);
+			if (curr_part_end > *endofpart)
+				*endofpart = curr_part_end;
+
+			part++;
+		}
+	} else {
+		/* Unknown partition table */
+		retval = -1;
+	}
+ abort:
+	return retval;
+}
+
+int check_partitions(int fd, char *dname, unsigned long long freesize)
+{
+	/*
+	 * Check where the last partition ends
+	 */
+	unsigned long long endofpart;
+	int ret;
+
+	if ((ret = get_last_partition_end(fd, &endofpart)) > 0) {
+		/* There appears to be a partition table here */
+		if (freesize == 0) {
+			/* partitions will not be visible in new device */
+			fprintf(stderr,
+				Name ": partition table exists on %s but will be lost or\n"
+				"       meaningless after creating array\n",
+				dname);
+			return 1;
+		} else if (endofpart > freesize) {
+			/* last partition overlaps metadata */
+			fprintf(stderr,
+				Name ": metadata will over-write last partition on %s.\n",
+				dname);
+			return 1;
+		}
+	}
+	return 0;
+}
+
 void get_one_disk(int mdfd, mdu_array_info_t *ainf, mdu_disk_info_t *disk)
 {
 	int d;
-- 
1.6.5.4