From 81e2673fb60a200a33bb064fbffe9e3956f37974 Mon Sep 17 00:00:00 2001 From: Goffredo Baroncelli Date: Mon, 22 Oct 2018 19:29:31 +0200 Subject: [PATCH] btrfs: Add support for reading a filesystem with a RAID 5 or RAID 6 profile Signed-off-by: Goffredo Baroncelli Signed-off-by: Daniel Kiper Reviewed-by: Daniel Kiper --- grub-core/fs/btrfs.c | 73 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c index be195448d..d484f093e 100644 --- a/grub-core/fs/btrfs.c +++ b/grub-core/fs/btrfs.c @@ -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: