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btrfs: Add support for reading a filesystem with a RAID 5 or RAID 6 profile

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Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Goffredo Baroncelli 2018-10-22 19:29:31 +02:00 committed by Vincent Batts
parent 5a0a15c05b
commit 3d822ff9b3
1 changed files with 73 additions and 0 deletions
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73
grub-core/fs/btrfs.c
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@ -119,6 +119,8 @@ struct grub_btrfs_chunk_item
#define GRUB_BTRFS_CHUNK_TYPE_RAID1 0x10
#define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED 0x20
#define GRUB_BTRFS_CHUNK_TYPE_RAID10 0x40
#define GRUB_BTRFS_CHUNK_TYPE_RAID5 0x80
#define GRUB_BTRFS_CHUNK_TYPE_RAID6 0x100
grub_uint8_t dummy2[0xc];
grub_uint16_t nstripes;
grub_uint16_t nsubstripes;
@ -764,6 +766,77 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
stripe_offset = low + chunk_stripe_length
* high;
csize = chunk_stripe_length - low;
break;
}
case GRUB_BTRFS_CHUNK_TYPE_RAID5:
case GRUB_BTRFS_CHUNK_TYPE_RAID6:
{
grub_uint64_t nparities, stripe_nr, high, low;
redundancy = 1; /* no redundancy for now */
if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5)
{
grub_dprintf ("btrfs", "RAID5\n");
nparities = 1;
}
else
{
grub_dprintf ("btrfs", "RAID6\n");
nparities = 2;
}
/*
* RAID 6 layout consists of several stripes spread over
* the disks, e.g.:
*
* Disk_0 Disk_1 Disk_2 Disk_3
* A0 B0 P0 Q0
* Q1 A1 B1 P1
* P2 Q2 A2 B2
*
* Note: placement of the parities depend on row number.
*
* Pay attention that the btrfs terminology may differ from
* terminology used in other RAID implementations, e.g. LVM,
* dm or md. The main difference is that btrfs calls contiguous
* block of data on a given disk, e.g. A0, stripe instead of chunk.
*
* The variables listed below have following meaning:
* - stripe_nr is the stripe number excluding the parities
* (A0 = 0, B0 = 1, A1 = 2, B1 = 3, etc.),
* - high is the row number (0 for A0...Q0, 1 for Q1...P1, etc.),
* - stripen is the disk number in a row (0 for A0, Q1, P2,
* 1 for B0, A1, Q2, etc.),
* - off is the logical address to read,
* - chunk_stripe_length is the size of a stripe (typically 64 KiB),
* - nstripes is the number of disks in a row,
* - low is the offset of the data inside a stripe,
* - stripe_offset is the data offset in an array,
* - csize is the "potential" data to read; it will be reduced
* to size if the latter is smaller,
* - nparities is the number of parities (1 for RAID 5, 2 for
* RAID 6); used only in RAID 5/6 code.
*/
stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
/*
* stripen is computed without the parities
* (0 for A0, A1, A2, 1 for B0, B1, B2, etc.).
*/
high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
/*
* The stripes are spread over the disks. Every each row their
* positions are shifted by 1 place. So, the real disks number
* change. Hence, we have to take into account current row number
* modulo nstripes (0 for A0, 1 for A1, 2 for A2, etc.).
*/
grub_divmod64 (high + stripen, nstripes, &stripen);
stripe_offset = chunk_stripe_length * high + low;
csize = chunk_stripe_length - low;
break;
}
default: