[PATCH v3 03/17] btrfs: allow remapped chunks to have zero stripes

[Mark Harmstone <mark@harmstone.com>]

When a chunk has been fully remapped, we are going to set its
num_stripes to 0, as it will no longer represent a physical location on
disk.

Change tree-checker to allow for this, and fix a couple of
divide-by-zeroes seen elsewhere.

Signed-off-by: Mark Harmstone <mark@harmstone.com>
---
 fs/btrfs/tree-checker.c | 65 ++++++++++++++++++++++++++++-------------
 fs/btrfs/volumes.c      | 13 ++++++++-
 2 files changed, 57 insertions(+), 21 deletions(-)

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 62f35338a555..59b1393e5018 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -816,6 +816,41 @@ static void chunk_err(const struct btrfs_fs_info *fs_info,
 	va_end(args);
 }
 
+static bool valid_stripe_count(u64 profile, u16 num_stripes,
+			       u16 sub_stripes)
+{
+	switch (profile) {
+	case BTRFS_BLOCK_GROUP_RAID0:
+		return true;
+	case BTRFS_BLOCK_GROUP_RAID10:
+		return sub_stripes ==
+			btrfs_raid_array[BTRFS_RAID_RAID10].sub_stripes;
+	case BTRFS_BLOCK_GROUP_RAID1:
+		return num_stripes ==
+			btrfs_raid_array[BTRFS_RAID_RAID1].devs_min;
+	case BTRFS_BLOCK_GROUP_RAID1C3:
+		return num_stripes ==
+			btrfs_raid_array[BTRFS_RAID_RAID1C3].devs_min;
+	case BTRFS_BLOCK_GROUP_RAID1C4:
+		return num_stripes ==
+			btrfs_raid_array[BTRFS_RAID_RAID1C4].devs_min;
+	case BTRFS_BLOCK_GROUP_RAID5:
+		return num_stripes >=
+			btrfs_raid_array[BTRFS_RAID_RAID5].devs_min;
+	case BTRFS_BLOCK_GROUP_RAID6:
+		return num_stripes >=
+			btrfs_raid_array[BTRFS_RAID_RAID6].devs_min;
+	case BTRFS_BLOCK_GROUP_DUP:
+		return num_stripes ==
+			btrfs_raid_array[BTRFS_RAID_DUP].dev_stripes;
+	case 0: /* SINGLE */
+		return num_stripes ==
+			btrfs_raid_array[BTRFS_RAID_SINGLE].dev_stripes;
+	default:
+		BUG();
+	}
+}
+
 /*
  * The common chunk check which could also work on super block sys chunk array.
  *
@@ -839,6 +874,7 @@ int btrfs_check_chunk_valid(const struct btrfs_fs_info *fs_info,
 	u64 features;
 	u32 chunk_sector_size;
 	bool mixed = false;
+	bool remapped;
 	int raid_index;
 	int nparity;
 	int ncopies;
@@ -862,12 +898,14 @@ int btrfs_check_chunk_valid(const struct btrfs_fs_info *fs_info,
 	ncopies = btrfs_raid_array[raid_index].ncopies;
 	nparity = btrfs_raid_array[raid_index].nparity;
 
-	if (unlikely(!num_stripes)) {
+	remapped = type & BTRFS_BLOCK_GROUP_REMAPPED;
+
+	if (unlikely(!remapped && !num_stripes)) {
 		chunk_err(fs_info, leaf, chunk, logical,
 			  "invalid chunk num_stripes, have %u", num_stripes);
 		return -EUCLEAN;
 	}
-	if (unlikely(num_stripes < ncopies)) {
+	if (unlikely(num_stripes != 0 && num_stripes < ncopies)) {
 		chunk_err(fs_info, leaf, chunk, logical,
 			  "invalid chunk num_stripes < ncopies, have %u < %d",
 			  num_stripes, ncopies);
@@ -965,22 +1003,9 @@ int btrfs_check_chunk_valid(const struct btrfs_fs_info *fs_info,
 		}
 	}
 
-	if (unlikely((type & BTRFS_BLOCK_GROUP_RAID10 &&
-		      sub_stripes != btrfs_raid_array[BTRFS_RAID_RAID10].sub_stripes) ||
-		     (type & BTRFS_BLOCK_GROUP_RAID1 &&
-		      num_stripes != btrfs_raid_array[BTRFS_RAID_RAID1].devs_min) ||
-		     (type & BTRFS_BLOCK_GROUP_RAID1C3 &&
-		      num_stripes != btrfs_raid_array[BTRFS_RAID_RAID1C3].devs_min) ||
-		     (type & BTRFS_BLOCK_GROUP_RAID1C4 &&
-		      num_stripes != btrfs_raid_array[BTRFS_RAID_RAID1C4].devs_min) ||
-		     (type & BTRFS_BLOCK_GROUP_RAID5 &&
-		      num_stripes < btrfs_raid_array[BTRFS_RAID_RAID5].devs_min) ||
-		     (type & BTRFS_BLOCK_GROUP_RAID6 &&
-		      num_stripes < btrfs_raid_array[BTRFS_RAID_RAID6].devs_min) ||
-		     (type & BTRFS_BLOCK_GROUP_DUP &&
-		      num_stripes != btrfs_raid_array[BTRFS_RAID_DUP].dev_stripes) ||
-		     ((type & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 &&
-		      num_stripes != btrfs_raid_array[BTRFS_RAID_SINGLE].dev_stripes))) {
+	if (!remapped &&
+	    !valid_stripe_count(type & BTRFS_BLOCK_GROUP_PROFILE_MASK,
+				num_stripes, sub_stripes)) {
 		chunk_err(fs_info, leaf, chunk, logical,
 			"invalid num_stripes:sub_stripes %u:%u for profile %llu",
 			num_stripes, sub_stripes,
@@ -1004,11 +1029,11 @@ static int check_leaf_chunk_item(struct extent_buffer *leaf,
 	struct btrfs_fs_info *fs_info = leaf->fs_info;
 	int num_stripes;
 
-	if (unlikely(btrfs_item_size(leaf, slot) < sizeof(struct btrfs_chunk))) {
+	if (unlikely(btrfs_item_size(leaf, slot) < offsetof(struct btrfs_chunk, stripe))) {
 		chunk_err(fs_info, leaf, chunk, key->offset,
 			"invalid chunk item size: have %u expect [%zu, %u)",
 			btrfs_item_size(leaf, slot),
-			sizeof(struct btrfs_chunk),
+			offsetof(struct btrfs_chunk, stripe),
 			BTRFS_LEAF_DATA_SIZE(fs_info));
 		return -EUCLEAN;
 	}
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e14b86e2996b..6750f6f0af59 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6145,6 +6145,12 @@ struct btrfs_discard_stripe *btrfs_map_discard(struct btrfs_fs_info *fs_info,
 		goto out_free_map;
 	}
 
+	/* avoid divide by zero on fully-remapped chunks */
+	if (map->num_stripes == 0) {
+		ret = -EOPNOTSUPP;
+		goto out_free_map;
+	}
+
 	offset = logical - map->start;
 	length = min_t(u64, map->start + map->chunk_len - logical, length);
 	*length_ret = length;
@@ -7088,7 +7094,12 @@ static int read_one_chunk(struct btrfs_key *key, struct extent_buffer *leaf,
 	 */
 	map->sub_stripes = btrfs_raid_array[index].sub_stripes;
 	map->verified_stripes = 0;
-	map->stripe_size = btrfs_calc_stripe_length(map);
+
+	if (num_stripes > 0)
+		map->stripe_size = btrfs_calc_stripe_length(map);
+	else
+		map->stripe_size = 0;
+
 	for (i = 0; i < num_stripes; i++) {
 		map->stripes[i].physical =
 			btrfs_stripe_offset_nr(leaf, chunk, i);
-- 
2.49.1