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# DP: Add support for specifying the root device using UUIDs on the
# DP: kernel command line like this without the need for an initrd:
# DP: linux ... root=UUID=ce40d6b2-18eb-4a75-aefe-7ddb0995ce63
# DP: Note: debugging code is kept in, commented out “//” style.
# DP:
# DP: Written © 2010 by Thorsten Glaser <tg@debian.org>
# DP: Idea from 1999 by David Balazic <david.balazic@uni-mb.si>
--- linux-2.6.36/block/genhd.c~ Wed Oct 20 22:30:22 2010
+++ linux-2.6.36/block/genhd.c Sat Nov 20 23:14:03 2010
@@ -35,7 +35,7 @@ struct kobject *block_depr;
static DEFINE_MUTEX(ext_devt_mutex);
static DEFINE_IDR(ext_devt_idr);
-static struct device_type disk_type;
+struct device_type disk_type;
/**
* disk_get_part - get partition
@@ -1019,7 +1019,7 @@ static char *block_devnode(struct device *dev, mode_t
return NULL;
}
-static struct device_type disk_type = {
+struct device_type disk_type = {
.name = "disk",
.groups = disk_attr_groups,
.release = disk_release,
--- linux-2.6.36/init/do_mounts.c~ Wed Oct 20 20:29:58 2010
+++ linux-2.6.36/init/do_mounts.c Sun Nov 21 18:37:36 2010
@@ -32,6 +32,132 @@ static int __initdata root_wait;
dev_t ROOT_DEV;
+#ifdef CONFIG_EXT2_FS
+/* support for root=UUID=ce40d6b2-18eb-4a75-aefe-7ddb0995ce63 bootargs */
+
+#include <linux/ext2_fs.h>
+
+__u8 root_dev_uuid[16];
+int root_dev_type; /* 0 = normal (/dev/hda1, 0301); 1 = UUID; 3 = bad */
+
+/* imported from block/genhd.c after removing its static qualifier */
+extern struct device_type disk_type;
+
+/* helper function */
+static __u8 __init fromhex(char c)
+{
+ if (c >= '0' && c <= '9')
+ return (c - '0');
+ c &= ~32;
+ if (c >= 'A' && c <= 'F')
+ return (c - 'A' + 10);
+ return (0xFF);
+}
+
+static void __init parse_uuid(const char *s)
+{
+ int i;
+ __u8 j, k;
+
+ if (strlen(s) != 36 || s[8] != '-' || s[13] != '-' ||
+ s[18] != '-' || s[23] != '-')
+ goto bad_uuid;
+ for (i = 0; i < 16; i++) {
+ if (*s == '-')
+ ++s;
+ j = fromhex(*s++);
+ k = fromhex(*s++);
+ if (j == 0xFF || k == 0xFF)
+ goto bad_uuid;
+ root_dev_uuid[i] = (j << 4) | k;
+ }
+ return;
+ bad_uuid:
+ /* we cannot panic here, defer */
+ root_dev_type = 3;
+}
+
+/* from drivers/md/md.c */
+static void __init initcode_bi_complete(struct bio *bio, int error)
+{
+ complete((struct completion*)bio->bi_private);
+}
+
+static int __init initcode_sync_page_read(struct block_device *bdev,
+ sector_t sector, int size, struct page *page)
+{
+ struct bio *bio = bio_alloc(GFP_NOIO, 1);
+ struct completion event;
+ int ret, rw = READ;
+
+ rw |= REQ_SYNC | REQ_UNPLUG;
+
+ bio->bi_bdev = bdev;
+ bio->bi_sector = sector;
+ bio_add_page(bio, page, size, 0);
+ init_completion(&event);
+ bio->bi_private = &event;
+ bio->bi_end_io = initcode_bi_complete;
+ submit_bio(rw, bio);
+ wait_for_completion(&event);
+
+ ret = test_bit(BIO_UPTODATE, &bio->bi_flags);
+ bio_put(bio);
+ /* 0 = failure */
+ return ret;
+}
+
+/* most of this taken from fs/ext2/super.c */
+static int __init check_dev(struct gendisk *thedisk, dev_t devt,
+ int blocksize, struct page *page)
+{
+ struct ext2_super_block * es;
+ struct block_device *bdev;
+ unsigned long sb_block = 1;
+ unsigned long logic_sb_block;
+ unsigned long offset = 0;
+ int rv = /* not found */ 0;
+ char bff[22];
+
+ bdev = bdget(devt);
+ if (blkdev_get(bdev, FMODE_READ)) {
+ printk(KERN_ERR "VFS: opening block device %s failed!\n",
+ format_dev_t(bff, devt));
+ return (0);
+ }
+
+ if (blocksize != BLOCK_SIZE) {
+ logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
+ offset = (sb_block*BLOCK_SIZE) % blocksize;
+ } else {
+ logic_sb_block = sb_block;
+ }
+
+// printk(KERN_ERR "D: attempting to read %d @%lu from "
+// "bdev %p devt %08X %s\n", blocksize, logic_sb_block,
+// bdev, devt, format_dev_t(bff, devt));
+ if (!initcode_sync_page_read(bdev, logic_sb_block, blocksize, page)) {
+// printk(KERN_ERR "D: failed!\n");
+ goto out;
+ }
+ es = (struct ext2_super_block *)(((char *)page_address(page)) + offset);
+ if (le16_to_cpu(es->s_magic) == EXT2_SUPER_MAGIC) {
+// printk(KERN_ERR "D: has uuid "
+// "%02X%02X%02X%02X-%02X%02X-%02X%02X-%02X%02X-%02X%02X%02X%02X%02X%02X\n",
+// es->s_uuid[0], es->s_uuid[1], es->s_uuid[2], es->s_uuid[3],
+// es->s_uuid[4], es->s_uuid[5], es->s_uuid[6], es->s_uuid[7],
+// es->s_uuid[8], es->s_uuid[9], es->s_uuid[10], es->s_uuid[11],
+// es->s_uuid[12], es->s_uuid[13], es->s_uuid[14], es->s_uuid[15]);
+ if (!memcmp(es->s_uuid, root_dev_uuid, 16))
+ rv = /* found */ 1;
+ }
+// else printk(KERN_ERR "D: bad ext2fs magic\n");
+ out:
+ blkdev_put(bdev, FMODE_READ);
+ return (rv);
+}
+#endif /* CONFIG_EXT2_FS for UUID support */
+
static int __init load_ramdisk(char *str)
{
rd_doload = simple_strtol(str,NULL,0) & 3;
@@ -148,6 +274,13 @@ done:
static int __init root_dev_setup(char *line)
{
strlcpy(saved_root_name, line, sizeof(saved_root_name));
+#ifdef CONFIG_EXT2_FS
+ root_dev_type = 0;
+ if (!strncmp(line, "UUID=", 5)) {
+ root_dev_type = 1;
+ parse_uuid(line + 5);
+ }
+#endif /* CONFIG_EXT2_FS for UUID support */
return 1;
}
@@ -333,6 +466,83 @@ void __init change_floppy(char *fmt, ...
void __init mount_root(void)
{
+#ifdef CONFIG_EXT2_FS
+ /* UUID support */
+// printk_all_partitions();
+ if (root_dev_type == 1) {
+ int blocksize;
+
+ /* from block/genhd.c printk_all_partitions */
+ struct class_dev_iter iter;
+ struct device *dev;
+
+ /* from drivers/md/md.c */
+ struct page *sb_page;
+
+ if (!(sb_page = alloc_page(GFP_KERNEL))) {
+ printk(KERN_ERR "VFS: no memory for bio page\n");
+ goto nomemforbio;
+ }
+
+// printk(KERN_ERR "D: root is: "
+// "%02X%02X%02X%02X-%02X%02X-%02X%02X-%02X%02X-%02X%02X%02X%02X%02X%02X\n",
+// root_dev_uuid[0], root_dev_uuid[1], root_dev_uuid[2], root_dev_uuid[3],
+// root_dev_uuid[4], root_dev_uuid[5], root_dev_uuid[6], root_dev_uuid[7],
+// root_dev_uuid[8], root_dev_uuid[9], root_dev_uuid[10], root_dev_uuid[11],
+// root_dev_uuid[12], root_dev_uuid[13], root_dev_uuid[14], root_dev_uuid[15]);
+ /* from block/genhd.c printk_all_partitions */
+// printk(KERN_ERR "D: begin iter\n");
+ class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
+ while (root_dev_type && (dev = class_dev_iter_next(&iter))) {
+// char bff[22];
+ struct gendisk *disk = dev_to_disk(dev);
+ struct disk_part_iter piter;
+ struct hd_struct *part;
+ if (get_capacity(disk) == 0 ||
+ (disk->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)) {
+// printk(KERN_ERR "D: ignoring\n");
+ continue;
+ }
+ blocksize = queue_logical_block_size(disk->queue);
+// printk(KERN_ERR "D: gendisk, blocksize %d "
+// "name '%s' devt %08X %s #part %d\n", blocksize,
+// disk->disk_name, dev->devt,
+// format_dev_t(bff, dev->devt),
+// disk_max_parts(disk));
+ disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0);
+ while (root_dev_type && (part = disk_part_iter_next(&piter))) {
+ /* avoid empty or too small partitions */
+// printk(KERN_ERR "D: part #%d start %llu "
+// "nr %llu\n", part->partno,
+// (__u64)part->start_sect,
+// (__u64)part->nr_sects);
+ if (part->nr_sects < 8)
+ continue;
+ if (check_dev(disk, MKDEV(MAJOR(dev->devt),
+ MINOR(dev->devt) + part->partno),
+ blocksize, sb_page)) {
+ ROOT_DEV = part_devt(part);
+// printk(KERN_ERR "D: got match!\n");
+ // comment out below for debugging
+ root_dev_type = 0;
+ }
+ }
+ disk_part_iter_exit(&piter);
+ }
+// printk(KERN_ERR "D: end iter\n");
+ class_dev_iter_exit(&iter);
+ put_page(sb_page);
+ }
+ nomemforbio:
+ if (root_dev_type == 1)
+ printk(KERN_ERR "VFS: Unable to find root by UUID %s.\n",
+ saved_root_name + 5);
+ else if (root_dev_type == 3)
+ /* execute deferred panic from parse_uuid */
+ panic("Badly formatted UUID %s was supplied as kernel "
+ "parameter root", saved_root_name + 5);
+#endif /* CONFIG_EXT2_FS for UUID support */
+
#ifdef CONFIG_ROOT_NFS
if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR) {
if (mount_nfs_root())
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