btrfs-progs: convert: Fix bugs in backup superblock migration

New convert has several bugs with backup superblock migration

1) Backup superblocks are not migrated due to incorrect condition
   Two wrong checks cause backup superblocks not to be migrated at all

2) Converted ext* image doesn't keep hole for backup superblocks
   Since we are creating file extents according to tmp_used, which has
   wiped out backup superblock ranges.
   In that case, later superblock migration will fail, since migration
   will insert file extent range into ext* image.

Fix above bugs will make convert on ext2 image filled about 100M data
successful.

Reported-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 45 insertions, 2 deletions

diff --git a/btrfs-convert.c b/btrfs-convert.c
index f78bfbf4..7cac304b 100644
--- a/btrfs-convert.c
+++ b/btrfs-convert.c
@@ -1263,12 +1263,55 @@ static int create_image_file_range(struct btrfs_trans_handle *trans,
 	struct btrfs_block_group_cache *bg_cache;
 	u64 len = *ret_len;
 	u64 disk_bytenr;
+	int i;
 	int ret;
 
 	BUG_ON(bytenr != round_down(bytenr, root->sectorsize));
 	BUG_ON(len != round_down(len, root->sectorsize));
 	len = min_t(u64, len, BTRFS_MAX_EXTENT_SIZE);
 
+	/*
+	 * Skip sb ranges first
+	 * [0, 1M), [sb_offset(1), +64K), [sb_offset(2), +64K].
+	 *
+	 * Or we will insert a hole into current image file, and later
+	 * migrate block will fail as there is already a file extent.
+	 */
+	if (bytenr < 1024 * 1024) {
+		*ret_len = 1024 * 1024 - bytenr;
+		return 0;
+	}
+	for (i = 1; i < BTRFS_SUPER_MIRROR_MAX; i++) {
+		u64 cur = btrfs_sb_offset(i);
+
+		if (bytenr >= cur && bytenr < cur + BTRFS_STRIPE_LEN) {
+			*ret_len = cur + BTRFS_STRIPE_LEN - bytenr;
+			return 0;
+		}
+	}
+	for (i = 1; i < BTRFS_SUPER_MIRROR_MAX; i++) {
+		u64 cur = btrfs_sb_offset(i);
+
+		/*
+		 *      |--reserved--|
+		 * |----range-------|
+		 * May still need to go through file extent inserts
+		 */
+		if (bytenr < cur && bytenr + len >= cur) {
+			len = min_t(u64, len, cur - bytenr);
+			break;
+		}
+		/*
+		 * |--reserved--|
+		 *      |---range---|
+		 * Drop out, no need to insert anything
+		 */
+		if (bytenr >= cur && bytenr < cur + BTRFS_STRIPE_LEN) {
+			*ret_len = cur + BTRFS_STRIPE_LEN - bytenr;
+			return 0;
+		}
+	}
+
 	cache = search_cache_extent(used, bytenr);
 	if (cache) {
 		if (cache->start <= bytenr) {
@@ -1425,7 +1468,7 @@ static int migrate_reserved_ranges(struct btrfs_trans_handle *trans,
 	/* second sb(fisrt sb is included in 0~1M) */
 	cur_off = btrfs_sb_offset(1);
 	cur_len = min(total_bytes, cur_off + BTRFS_STRIPE_LEN) - cur_off;
-	if (cur_off < total_bytes)
+	if (cur_off > total_bytes)
 		return ret;
 	ret = migrate_one_reserved_range(trans, root, used, inode, fd, ino,
 					 cur_off, cur_len, datacsum);
@@ -1435,7 +1478,7 @@ static int migrate_reserved_ranges(struct btrfs_trans_handle *trans,
 	/* Last sb */
 	cur_off = btrfs_sb_offset(2);
 	cur_len = min(total_bytes, cur_off + BTRFS_STRIPE_LEN) - cur_off;
-	if (cur_off < total_bytes)
+	if (cur_off > total_bytes)
 		return ret;
 	ret = migrate_one_reserved_range(trans, root, used, inode, fd, ino,
 					 cur_off, cur_len, datacsum);