Btrfs: RAID5 and RAID6
This builds on David Woodhouse's original Btrfs raid5/6 implementation.
The code has changed quite a bit, blame Chris Mason for any bugs.
Read/modify/write is done after the higher levels of the filesystem have
prepared a given bio. This means the higher layers are not responsible
for building full stripes, and they don't need to query for the topology
of the extents that may get allocated during delayed allocation runs.
It also means different files can easily share the same stripe.
But, it does expose us to incorrect parity if we crash or lose power
while doing a read/modify/write cycle. This will be addressed in a
later commit.
Scrub is unable to repair crc errors on raid5/6 chunks.
Discard does not work on raid5/6 (yet)
The stripe size is fixed at 64KiB per disk. This will be tunable
in a later commit.
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 86ecca4..3b9fb47 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1895,13 +1895,11 @@
if (ret)
err = ret;
- if (did_repair) {
- ret = clear_extent_bits(&BTRFS_I(inode)->io_tree, rec->start,
- rec->start + rec->len - 1,
- EXTENT_DAMAGED, GFP_NOFS);
- if (ret && !err)
- err = ret;
- }
+ ret = clear_extent_bits(&BTRFS_I(inode)->io_tree, rec->start,
+ rec->start + rec->len - 1,
+ EXTENT_DAMAGED, GFP_NOFS);
+ if (ret && !err)
+ err = ret;
kfree(rec);
return err;
@@ -1932,10 +1930,15 @@
u64 map_length = 0;
u64 sector;
struct btrfs_bio *bbio = NULL;
+ struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
int ret;
BUG_ON(!mirror_num);
+ /* we can't repair anything in raid56 yet */
+ if (btrfs_is_parity_mirror(map_tree, logical, length, mirror_num))
+ return 0;
+
bio = bio_alloc(GFP_NOFS, 1);
if (!bio)
return -EIO;
@@ -2052,6 +2055,7 @@
failrec->failed_mirror);
did_repair = !ret;
}
+ ret = 0;
}
out: