New function reset_tree_block_csum() will do the black magic to reset
csum for a tree block in-place.
This provides the basis to the whole tree csum resetting function.
Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
---
cmds-check.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/cmds-check.c b/cmds-check.c
index 5817ecf..e4b4f4a 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -9137,6 +9137,62 @@ static u16 report_root_corrupted(struct btrfs_fs_info *fs_info,
return ret;
}
+/*
+ * Black magics to reset the csum of a tree block.
+ * The evil part is to modify block without transaction/cow.
+ *
+ * Return 0 if the csum is OK or reset the csum
+ * Return <0 if error happened
+ */
+static int reset_tree_block_csum(struct btrfs_fs_info *fs_info,
+ u64 bytenr, u32 len)
+{
+ /*
+ * read_tree_block just use root as ladder to reach fs_info,
+ * so use chunk_root since it must be OK.
+ */
+ struct btrfs_root *root = fs_info->chunk_root;
+ struct extent_buffer *eb;
+ char *buf = NULL;
+ u32 crc;
+ int ret = 0;
+
+ eb = read_tree_block(root, bytenr, len, 0);
+ /* No need to do anything since its csum is OK */
+ if (extent_buffer_uptodate(eb))
+ goto out;
+
+ buf = malloc(len);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ ret = read_data_from_disk(fs_info, buf, bytenr, len, 0);
+ if (ret < 0)
+ goto out;
+ crc = ~(u32)0;
+ crc = btrfs_csum_data(NULL, buf + BTRFS_CSUM_SIZE, crc,
+ len - BTRFS_CSUM_SIZE);
+ btrfs_csum_final(crc, buf);
+ ret = write_data_to_disk(fs_info, buf, bytenr, len, 0);
+ if (ret < 0)
+ goto out;
+
+ /* Make sure now we can read the tree block */
+ eb = read_tree_block(root, bytenr, len, 0);
+ if (!extent_buffer_uptodate(eb)) {
+ if (IS_ERR(eb))
+ ret = PTR_ERR(eb);
+ else
+ ret = -EINVAL;
+ goto out;
+ }
+out:
+ free(buf);
+ free_extent_buffer(eb);
+ return ret;
+}
+
const char * const cmd_check_usage[] = {
"btrfs check [options] <device>",
"Check an unmounted btrfs filesystem.",
--
2.2.2
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