Btrfs: Retry metadata reads in the face of checksum failures

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 35 insertions, 4 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 008d3640e8c2..3b927f698320 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -788,9 +788,31 @@ void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree)
         }
 }
 
+int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len)
+{
+        struct extent_map *em;
+        struct map_lookup *map;
+        struct extent_map_tree *em_tree = &map_tree->map_tree;
+        int ret;
+
+        spin_lock(&em_tree->lock);
+        em = lookup_extent_mapping(em_tree, logical, len);
+        BUG_ON(!em);
+
+        BUG_ON(em->start > logical || em->start + em->len < logical);
+        map = (struct map_lookup *)em->bdev;
+        if (map->type & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1))
+                ret = map->num_stripes;
+        else
+                ret = 1;
+        free_extent_map(em);
+        spin_unlock(&em_tree->lock);
+        return ret;
+}
+
 int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
                     u64 logical, u64 *length,
-                    struct btrfs_multi_bio **multi_ret)
+                    struct btrfs_multi_bio **multi_ret, int mirror_num)
 {
         struct extent_map *em;
         struct map_lookup *map;
@@ -822,6 +844,9 @@ again:
         map = (struct map_lookup *)em->bdev;
         offset = logical - em->start;
 
+        if (mirror_num > map->num_stripes)
+                mirror_num = 0;
+
         /* if our multi bio struct is too small, back off and try again */
         if (multi_ret && (rw & (1 << BIO_RW)) &&
             stripes_allocated < map->num_stripes &&
@@ -862,7 +887,9 @@ again:
         if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
                 if (rw & (1 << BIO_RW))
                         multi->num_stripes = map->num_stripes;
-                else {
+                else if (mirror_num) {
+                        stripe_index = mirror_num - 1;
+                } else {
                         int i;
                         u64 least = (u64)-1;
                         struct btrfs_device *cur;
@@ -880,6 +907,8 @@ again:
         } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
                 if (rw & (1 << BIO_RW))
                         multi->num_stripes = map->num_stripes;
+                else if (mirror_num)
+                        stripe_index = mirror_num - 1;
         } else {
                 /*
                  * after this do_div call, stripe_nr is the number of stripes
@@ -938,7 +967,8 @@ static int end_bio_multi_stripe(struct bio *bio,
 #endif
 }
 
-int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio)
+int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
+                  int mirror_num)
 {
         struct btrfs_mapping_tree *map_tree;
         struct btrfs_device *dev;
@@ -960,7 +990,8 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio)
         map_tree = &root->fs_info->mapping_tree;
         map_length = length;
 
-        ret = btrfs_map_block(map_tree, rw, logical, &map_length, &multi);
+        ret = btrfs_map_block(map_tree, rw, logical, &map_length, &multi,
+                              mirror_num);
         BUG_ON(ret);
 
         total_devs = multi->num_stripes;