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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Goffredo Baroncelli <kreijack@inwind.it>
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Date: Mon, 22 Oct 2018 19:29:31 +0200
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Subject: [PATCH] btrfs: Add support for reading a filesystem with a RAID 5 or
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RAID 6 profile
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Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
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Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit 81e2673fb60a200a33bb064fbffe9e3956f37974)
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---
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grub-core/fs/btrfs.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
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1 file changed, 73 insertions(+)
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diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
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index a401374690..6f17f5d0eb 100644
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--- a/grub-core/fs/btrfs.c
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+++ b/grub-core/fs/btrfs.c
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@@ -120,6 +120,8 @@ struct grub_btrfs_chunk_item
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#define GRUB_BTRFS_CHUNK_TYPE_RAID1 0x10
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#define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED 0x20
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#define GRUB_BTRFS_CHUNK_TYPE_RAID10 0x40
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+#define GRUB_BTRFS_CHUNK_TYPE_RAID5 0x80
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+#define GRUB_BTRFS_CHUNK_TYPE_RAID6 0x100
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grub_uint8_t dummy2[0xc];
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grub_uint16_t nstripes;
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grub_uint16_t nsubstripes;
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@@ -785,6 +787,77 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
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stripe_offset = low + chunk_stripe_length
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* high;
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csize = chunk_stripe_length - low;
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+ break;
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+ }
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+ case GRUB_BTRFS_CHUNK_TYPE_RAID5:
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+ case GRUB_BTRFS_CHUNK_TYPE_RAID6:
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+ {
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+ grub_uint64_t nparities, stripe_nr, high, low;
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+
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+ redundancy = 1; /* no redundancy for now */
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+
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+ if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5)
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+ {
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+ grub_dprintf ("btrfs", "RAID5\n");
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+ nparities = 1;
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+ }
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+ else
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+ {
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+ grub_dprintf ("btrfs", "RAID6\n");
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+ nparities = 2;
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+ }
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+
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+ /*
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+ * RAID 6 layout consists of several stripes spread over
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+ * the disks, e.g.:
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+ *
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+ * Disk_0 Disk_1 Disk_2 Disk_3
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+ * A0 B0 P0 Q0
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+ * Q1 A1 B1 P1
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+ * P2 Q2 A2 B2
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+ *
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+ * Note: placement of the parities depend on row number.
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+ *
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+ * Pay attention that the btrfs terminology may differ from
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+ * terminology used in other RAID implementations, e.g. LVM,
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+ * dm or md. The main difference is that btrfs calls contiguous
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+ * block of data on a given disk, e.g. A0, stripe instead of chunk.
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+ *
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+ * The variables listed below have following meaning:
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+ * - stripe_nr is the stripe number excluding the parities
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+ * (A0 = 0, B0 = 1, A1 = 2, B1 = 3, etc.),
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+ * - high is the row number (0 for A0...Q0, 1 for Q1...P1, etc.),
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+ * - stripen is the disk number in a row (0 for A0, Q1, P2,
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+ * 1 for B0, A1, Q2, etc.),
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+ * - off is the logical address to read,
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+ * - chunk_stripe_length is the size of a stripe (typically 64 KiB),
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+ * - nstripes is the number of disks in a row,
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+ * - low is the offset of the data inside a stripe,
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+ * - stripe_offset is the data offset in an array,
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+ * - csize is the "potential" data to read; it will be reduced
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+ * to size if the latter is smaller,
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+ * - nparities is the number of parities (1 for RAID 5, 2 for
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+ * RAID 6); used only in RAID 5/6 code.
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+ */
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+ stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
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+
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+ /*
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+ * stripen is computed without the parities
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+ * (0 for A0, A1, A2, 1 for B0, B1, B2, etc.).
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+ */
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+ high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
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+
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+ /*
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+ * The stripes are spread over the disks. Every each row their
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+ * positions are shifted by 1 place. So, the real disks number
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+ * change. Hence, we have to take into account current row number
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+ * modulo nstripes (0 for A0, 1 for A1, 2 for A2, etc.).
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+ */
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+ grub_divmod64 (high + stripen, nstripes, &stripen);
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+
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+ stripe_offset = chunk_stripe_length * high + low;
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+ csize = chunk_stripe_length - low;
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+
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break;
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}
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default:
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