Btrfs: fix nodatasum handling in balancing code

Checksums on data can be disabled by mount option, so it's
possible some data extents don't have checksums or have
invalid checksums. This causes trouble for data relocation.
This patch contains following things to make data relocation
work.

1) make nodatasum/nodatacow mount option only affects new
files. Checksums and COW on data are only controlled by the
inode flags.

2) check the existence of checksum in the nodatacow checker.
If checksums exist, force COW the data extent. This ensure that
checksum for a given block is either valid or does not exist.

3) update data relocation code to properly handle the case
of checksum missing.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 111 insertions, 3 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 3ebef871ee6..df0447632db 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -140,6 +140,7 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
+
 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 			  struct bio *bio, u32 *dst)
 {
@@ -185,9 +186,16 @@ int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 				if (ret == -ENOENT || ret == -EFBIG)
 					ret = 0;
 				sum = 0;
-				printk("no csum found for inode %lu start "
-				       "%llu\n", inode->i_ino,
-				       (unsigned long long)offset);
+				if (BTRFS_I(inode)->root->root_key.objectid ==
+				    BTRFS_DATA_RELOC_TREE_OBJECTID) {
+					set_extent_bits(io_tree, offset,
+						offset + bvec->bv_len - 1,
+						EXTENT_NODATASUM, GFP_NOFS);
+				} else {
+					printk("no csum found for inode %lu "
+					       "start %llu\n", inode->i_ino,
+					       (unsigned long long)offset);
+				}
 				item = NULL;
 				btrfs_release_path(root, path);
 				goto found;
@@ -228,6 +236,106 @@ found:
 	return 0;
 }
 
+int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
+			     struct list_head *list)
+{
+	struct btrfs_key key;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	struct btrfs_ordered_sum *sums;
+	struct btrfs_sector_sum *sector_sum;
+	struct btrfs_csum_item *item;
+	unsigned long offset;
+	int ret;
+	size_t size;
+	u64 csum_end;
+	u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
+
+	path = btrfs_alloc_path();
+	BUG_ON(!path);
+
+	key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+	key.offset = start;
+	key.type = BTRFS_EXTENT_CSUM_KEY;
+
+	ret = btrfs_search_slot(NULL, root->fs_info->csum_root,
+				&key, path, 0, 0);
+	if (ret < 0)
+		goto fail;
+	if (ret > 0 && path->slots[0] > 0) {
+		leaf = path->nodes[0];
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
+		if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
+		    key.type == BTRFS_EXTENT_CSUM_KEY) {
+			offset = (start - key.offset) >>
+				 root->fs_info->sb->s_blocksize_bits;
+			if (offset * csum_size <
+			    btrfs_item_size_nr(leaf, path->slots[0] - 1))
+				path->slots[0]--;
+		}
+	}
+
+	while (start <= end) {
+		leaf = path->nodes[0];
+		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+			ret = btrfs_next_leaf(root->fs_info->csum_root, path);
+			if (ret < 0)
+				goto fail;
+			if (ret > 0)
+				break;
+			leaf = path->nodes[0];
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+		if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+		    key.type != BTRFS_EXTENT_CSUM_KEY)
+			break;
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+		if (key.offset > end)
+			break;
+
+		if (key.offset > start)
+			start = key.offset;
+
+		size = btrfs_item_size_nr(leaf, path->slots[0]);
+		csum_end = key.offset + (size / csum_size) * root->sectorsize;
+
+		size = min(csum_end, end + 1) - start;
+		sums = kzalloc(btrfs_ordered_sum_size(root, size), GFP_NOFS);
+		BUG_ON(!sums);
+
+		sector_sum = sums->sums;
+		sums->bytenr = start;
+		sums->len = size;
+
+		offset = (start - key.offset) >>
+			 root->fs_info->sb->s_blocksize_bits;
+		offset *= csum_size;
+
+		item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				      struct btrfs_csum_item);
+		while (size > 0) {
+			read_extent_buffer(path->nodes[0], &sector_sum->sum,
+					   ((unsigned long)item) + offset,
+					   csum_size);
+			sector_sum->bytenr = start;
+
+			size -= root->sectorsize;
+			start += root->sectorsize;
+			offset += csum_size;
+			sector_sum++;
+		}
+		list_add_tail(&sums->list, list);
+
+		path->slots[0]++;
+	}
+	ret = 0;
+fail:
+	btrfs_free_path(path);
+	return ret;
+}
+
 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 		       struct bio *bio, u64 file_start, int contig)
 {