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authorWill Drewry <wad@chromium.org>2011-11-02 13:38:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-11-02 16:07:01 -0700
commit79975f1327850ef198ada994c2fc44b7d1ea8935 (patch)
treecff91dd5d697858a2cc84da392aa87e61a0bf3d2 /init/do_mounts.c
parentf567a18590742b811287b7512fb0908deac4eef7 (diff)
downloadlinux-aarch64-79975f1327850ef198ada994c2fc44b7d1ea8935.tar.gz
init: add root=PARTUUID=UUID/PARTNROFF=%d support
Expand root=PARTUUID=UUID syntax to support selecting a root partition by integer offset from a known, unique partition. This approach provides similar properties to specifying a device and partition number, but using the UUID as the unique path prior to evaluating the offset. For example, root=PARTUUID=99DE9194-FC15-4223-9192-FC243948F88B/PARTNROFF=1 selects the partition with UUID 99DE.. then select the next partition. This change is motivated by a particular usecase in Chromium OS where the bootloader can easily determine what partition it is on (by UUID) but doesn't perform general partition table walking. That said, support for this model provides a direct mechanism for the user to modify the root partition to boot without specifically needing to extract each UUID or update the bootloader explicitly when the root partition UUID is changed (if it is recreated to be larger, for instance). Pinning to a /boot-style partition UUID allows the arbitrary root partition reconfiguration/modifications with slightly less ambiguity than just [dev][partition] and less stringency than the specific root partition UUID. [sfr@canb.auug.org.au: fix init sections warning] Signed-off-by: Will Drewry <wad@chromium.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'init/do_mounts.c')
-rw-r--r--init/do_mounts.c48
1 files changed, 43 insertions, 5 deletions
diff --git a/init/do_mounts.c b/init/do_mounts.c
index c0851a8e030c..0f6e1d985a3b 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -28,7 +28,7 @@ int __initdata rd_doload; /* 1 = load RAM disk, 0 = don't load */
int root_mountflags = MS_RDONLY | MS_SILENT;
static char * __initdata root_device_name;
static char __initdata saved_root_name[64];
-static int __initdata root_wait;
+static int root_wait;
dev_t ROOT_DEV;
@@ -85,12 +85,15 @@ no_match:
/**
* devt_from_partuuid - looks up the dev_t of a partition by its UUID
- * @uuid: 36 byte char array containing a hex ascii UUID
+ * @uuid: min 36 byte char array containing a hex ascii UUID
*
* The function will return the first partition which contains a matching
* UUID value in its partition_meta_info struct. This does not search
* by filesystem UUIDs.
*
+ * If @uuid is followed by a "/PARTNROFF=%d", then the number will be
+ * extracted and used as an offset from the partition identified by the UUID.
+ *
* Returns the matching dev_t on success or 0 on failure.
*/
static dev_t devt_from_partuuid(char *uuid_str)
@@ -98,6 +101,28 @@ static dev_t devt_from_partuuid(char *uuid_str)
dev_t res = 0;
struct device *dev = NULL;
u8 uuid[16];
+ struct gendisk *disk;
+ struct hd_struct *part;
+ int offset = 0;
+
+ if (strlen(uuid_str) < 36)
+ goto done;
+
+ /* Check for optional partition number offset attributes. */
+ if (uuid_str[36]) {
+ char c = 0;
+ /* Explicitly fail on poor PARTUUID syntax. */
+ if (sscanf(&uuid_str[36],
+ "/PARTNROFF=%d%c", &offset, &c) != 1) {
+ printk(KERN_ERR "VFS: PARTUUID= is invalid.\n"
+ "Expected PARTUUID=<valid-uuid-id>[/PARTNROFF=%%d]\n");
+ if (root_wait)
+ printk(KERN_ERR
+ "Disabling rootwait; root= is invalid.\n");
+ root_wait = 0;
+ goto done;
+ }
+ }
/* Pack the requested UUID in the expected format. */
part_pack_uuid(uuid_str, uuid);
@@ -107,8 +132,21 @@ static dev_t devt_from_partuuid(char *uuid_str)
goto done;
res = dev->devt;
- put_device(dev);
+ /* Attempt to find the partition by offset. */
+ if (!offset)
+ goto no_offset;
+
+ res = 0;
+ disk = part_to_disk(dev_to_part(dev));
+ part = disk_get_part(disk, dev_to_part(dev)->partno + offset);
+ if (part) {
+ res = part_devt(part);
+ put_device(part_to_dev(part));
+ }
+
+no_offset:
+ put_device(dev);
done:
return res;
}
@@ -126,6 +164,8 @@ done:
* used when disk name of partitioned disk ends on a digit.
* 6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
* unique id of a partition if the partition table provides it.
+ * 7) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
+ * a partition with a known unique id.
*
* If name doesn't have fall into the categories above, we return (0,0).
* block_class is used to check if something is a disk name. If the disk
@@ -143,8 +183,6 @@ dev_t name_to_dev_t(char *name)
#ifdef CONFIG_BLOCK
if (strncmp(name, "PARTUUID=", 9) == 0) {
name += 9;
- if (strlen(name) != 36)
- goto fail;
res = devt_from_partuuid(name);
if (!res)
goto fail;