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@nvidia.com> Cc: Tejun Heo <tj@kernel.org> Cc: Will Drewry <wad@chromium.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -94,6 +94,17 @@ static int aix_magic_present(struct parsed_partitions *state, unsigned char *p)
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return ret;
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}
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static void set_info(struct parsed_partitions *state, int slot,
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u32 disksig)
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{
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struct partition_meta_info *info = &state->parts[slot].info;
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snprintf(info->uuid, sizeof(info->uuid), "%08x-%02x", disksig,
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slot);
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info->volname[0] = 0;
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state->parts[slot].has_info = true;
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}
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/*
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* Create devices for each logical partition in an extended partition.
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* The logical partitions form a linked list, with each entry being
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@ -106,7 +117,8 @@ static int aix_magic_present(struct parsed_partitions *state, unsigned char *p)
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*/
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static void parse_extended(struct parsed_partitions *state,
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sector_t first_sector, sector_t first_size)
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sector_t first_sector, sector_t first_size,
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u32 disksig)
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{
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struct partition *p;
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Sector sect;
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@ -166,6 +178,7 @@ static void parse_extended(struct parsed_partitions *state,
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}
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put_partition(state, state->next, next, size);
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set_info(state, state->next, disksig);
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if (SYS_IND(p) == LINUX_RAID_PARTITION)
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state->parts[state->next].flags = ADDPART_FLAG_RAID;
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loopct = 0;
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@ -437,6 +450,7 @@ int msdos_partition(struct parsed_partitions *state)
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struct partition *p;
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struct fat_boot_sector *fb;
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int slot;
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u32 disksig;
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data = read_part_sector(state, 0, §);
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if (!data)
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@ -491,6 +505,8 @@ int msdos_partition(struct parsed_partitions *state)
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#endif
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p = (struct partition *) (data + 0x1be);
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disksig = le32_to_cpup((__le32 *)(data + 0x1b8));
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/*
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* Look for partitions in two passes:
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* First find the primary and DOS-type extended partitions.
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@ -515,11 +531,12 @@ int msdos_partition(struct parsed_partitions *state)
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put_partition(state, slot, start, n);
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strlcat(state->pp_buf, " <", PAGE_SIZE);
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parse_extended(state, start, size);
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parse_extended(state, start, size, disksig);
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strlcat(state->pp_buf, " >", PAGE_SIZE);
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continue;
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}
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put_partition(state, slot, start, size);
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set_info(state, slot, disksig);
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if (SYS_IND(p) == LINUX_RAID_PARTITION)
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state->parts[slot].flags = ADDPART_FLAG_RAID;
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if (SYS_IND(p) == DM6_PARTITION)
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@ -189,6 +189,10 @@ done:
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* used when disk name of partitioned disk ends on a digit.
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* 6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
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* unique id of a partition if the partition table provides it.
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* The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
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* partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
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* filled hex representation of the 32-bit "NT disk signature", and PP
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* is a zero-filled hex representation of the 1-based partition number.
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* 7) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
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* a partition with a known unique id.
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*
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