Btrfs: Set real mirror number for read operation on RAID0/5/6

We need real mirror number for RAID0/5/6 when reading data, or if read error
happens, we would pass 0 as the number of the mirror on which the io error
happens. It is wrong and would cause the filesystem read the data from the
corrupted mirror again.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 77d7fbc0fa47928f350a7fa21aefe7d1a8fd5f86..63e632746d8a95a29f716bf12b1a8f9c0c1e74b1 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5073,6 +5073,8 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                        num_stripes = min_t(u64, map->num_stripes,
                                            stripe_nr_end - stripe_nr_orig);
                stripe_index = do_div(stripe_nr, map->num_stripes);
+               if (!(rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS)))
+                       mirror_num = 1;
        } else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
                if (rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS))
                        num_stripes = map->num_stripes;
@@ -5176,6 +5178,9 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                        /* We distribute the parity blocks across stripes */
                        tmp = stripe_nr + stripe_index;
                        stripe_index = do_div(tmp, map->num_stripes);
+                       if (!(rw & (REQ_WRITE | REQ_DISCARD |
+                                   REQ_GET_READ_MIRRORS)) && mirror_num <= 1)
+                               mirror_num = 1;
                }
        } else {
                /*