The patch titled
Subject: block: partition: msdos: provide UUIDs for partitions
has been added to the -mm tree. Its filename is
block-partition-msdos-provide-uuids-for-partitions.patch
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------------------------------------------------------
From: Stephen Warren <swarren@xxxxxxxxxx>
Subject: block: partition: msdos: provide UUIDs for partitions
The MSDOS/MBR partition table includes a 32-bit unique ID, often referred
to as the NT disk signature. When combined with a partition number within
the table, this can form a unique ID similar in concept to EFI/GPT's
partition UUID. Constructing and recording this value in struct
partition_meta_info allows MSDOS partitions to be referred to on the
kernel command-line using the following syntax:
root=PARTUUID=0002dd75-01
Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Cc: Kay Sievers <kay.sievers@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
block/partitions/msdos.c | 21 +++++++++++++++++++--
init/do_mounts.c | 4 ++++
2 files changed, 23 insertions(+), 2 deletions(-)
diff -puN block/partitions/msdos.c~block-partition-msdos-provide-uuids-for-partitions block/partitions/msdos.c
--- a/block/partitions/msdos.c~block-partition-msdos-provide-uuids-for-partitions
+++ a/block/partitions/msdos.c
@@ -94,6 +94,17 @@ static int aix_magic_present(struct pars
return ret;
}
+static void set_info(struct parsed_partitions *state, int slot,
+ u32 disksig)
+{
+ struct partition_meta_info *info = &state->parts[slot].info;
+
+ snprintf(info->uuid, sizeof(info->uuid), "%08x-%02x", disksig,
+ slot);
+ info->volname[0] = 0;
+ state->parts[slot].has_info = true;
+}
+
/*
* Create devices for each logical partition in an extended partition.
* The logical partitions form a linked list, with each entry being
@@ -106,7 +117,8 @@ static int aix_magic_present(struct pars
*/
static void parse_extended(struct parsed_partitions *state,
- sector_t first_sector, sector_t first_size)
+ sector_t first_sector, sector_t first_size,
+ u32 disksig)
{
struct partition *p;
Sector sect;
@@ -166,6 +178,7 @@ static void parse_extended(struct parsed
}
put_partition(state, state->next, next, size);
+ set_info(state, state->next, disksig);
if (SYS_IND(p) == LINUX_RAID_PARTITION)
state->parts[state->next].flags = ADDPART_FLAG_RAID;
loopct = 0;
@@ -437,6 +450,7 @@ int msdos_partition(struct parsed_partit
struct partition *p;
struct fat_boot_sector *fb;
int slot;
+ u32 disksig;
data = read_part_sector(state, 0, §);
if (!data)
@@ -491,6 +505,8 @@ int msdos_partition(struct parsed_partit
#endif
p = (struct partition *) (data + 0x1be);
+ disksig = le32_to_cpup((__le32 *)(data + 0x1b8));
+
/*
* Look for partitions in two passes:
* First find the primary and DOS-type extended partitions.
@@ -515,11 +531,12 @@ int msdos_partition(struct parsed_partit
put_partition(state, slot, start, n);
strlcat(state->pp_buf, " <", PAGE_SIZE);
- parse_extended(state, start, size);
+ parse_extended(state, start, size, disksig);
strlcat(state->pp_buf, " >", PAGE_SIZE);
continue;
}
put_partition(state, slot, start, size);
+ set_info(state, slot, disksig);
if (SYS_IND(p) == LINUX_RAID_PARTITION)
state->parts[slot].flags = ADDPART_FLAG_RAID;
if (SYS_IND(p) == DM6_PARTITION)
diff -puN init/do_mounts.c~block-partition-msdos-provide-uuids-for-partitions init/do_mounts.c
--- a/init/do_mounts.c~block-partition-msdos-provide-uuids-for-partitions
+++ a/init/do_mounts.c
@@ -189,6 +189,10 @@ 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.
+ * The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
+ * partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
+ * filled hex representation of the 32-bit "NT disk signature", and PP
+ * is a zero-filled hex representation of the 1-based partition number.
* 7) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
* a partition with a known unique id.
*
_
Patches currently in -mm which might be from swarren@xxxxxxxxxx are
linux-next.patch
block-store-partition_meta_infouuid-as-a-string.patch
init-reduce-partuuid-min-length-to-1-from-36.patch
block-partition-msdos-provide-uuids-for-partitions.patch
rtc-add-max8907-rtc-driver.patch
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