btrfs-progs: fix-data-checksum: show affected files

Previously "btrfs rescue fix-data-checksum" only showed affected logical
bytenr, which is not helpful to determine which files are affected.

Enhance the output by also printing the affected subvolumes (in numeric
form), and the file paths inside that subvolume.

The example looks like this:

  logical=13631488 corrtuped mirrors=1 affected files:
    (subvolume 5)/foo
    (subvolume 5)/dir/bar
  logical=13635584 corrtuped mirrors=1 affected files:
    (subvolume 5)/foo
    (subvolume 5)/dir/bar

Although the end result is still not perfect, it's much easier to find
out which files are affected.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: adam900710

cmds/rescue-fix-data-checksum.c

@@ -18,6 +18,7 @@
 #include "kernel-shared/disk-io.h"
 #include "kernel-shared/ctree.h"
 #include "kernel-shared/volumes.h"
+#include "kernel-shared/backref.h"
 #include "common/messages.h"
 #include "common/open-utils.h"
 #include "cmds/rescue.h"
@@ -159,6 +160,50 @@ static int iterate_one_csum_item(struct btrfs_fs_info *fs_info, struct btrfs_pat
 	return ret;
 }
 
+static int print_filenames(u64 ino, u64 offset, u64 rootid, void *ctx)
+{
+	struct btrfs_fs_info *fs_info = ctx;
+	struct btrfs_root *root;
+	struct btrfs_key key;
+	struct inode_fs_paths *ipath;
+	struct btrfs_path path = { 0 };
+	int ret;
+
+	key.objectid = rootid;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = (u64)-1;
+
+	root = btrfs_read_fs_root(fs_info, &key);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		errno = -ret;
+		error("failed to get subvolume %llu: %m", rootid);
+		return ret;
+	}
+	ipath = init_ipath(128 * BTRFS_PATH_NAME_MAX, root, &path);
+	if (IS_ERR(ipath)) {
+		ret = PTR_ERR(ipath);
+		errno = -ret;
+		error("failed to initialize ipath: %m");
+		return ret;
+	}
+	ret = paths_from_inode(ino, ipath);
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to resolve root %llu ino %llu to paths: %m", rootid, ino);
+		goto out;
+	}
+	for (int i = 0; i < ipath->fspath->elem_cnt; i++)
+		pr_verbose(LOG_DEFAULT, "  (subvolume %llu)/%s\n", rootid,
+			   (char *)ipath->fspath->val[i]);
+	if (ipath->fspath->elem_missed)
+		pr_verbose(LOG_DEFAULT, "  (subvolume %llu) %d files not printed\n",
+			   rootid, ipath->fspath->elem_missed);
+out:
+	free_ipath(ipath);
+	return ret;
+}
+
 static int iterate_csum_root(struct btrfs_fs_info *fs_info, struct btrfs_root *csum_root)
 {
 	struct btrfs_path path = { 0 };
@@ -198,9 +243,10 @@ static int iterate_csum_root(struct btrfs_fs_info *fs_info, struct btrfs_root *c
 	return ret;
 }
 
-static void report_corrupted_blocks(void)
+static void report_corrupted_blocks(struct btrfs_fs_info *fs_info)
 {
 	struct corrupted_block *entry;
+	struct btrfs_path path = { 0 };
 
 	if (list_empty(&corrupted_blocks)) {
 		pr_verbose(LOG_DEFAULT, "no data checksum mismatch found\n");
@@ -209,6 +255,7 @@ static void report_corrupted_blocks(void)
 
 	list_for_each_entry(entry, &corrupted_blocks, list) {
 		bool has_printed = false;
+		int ret;
 
 		pr_verbose(LOG_DEFAULT, "logical=%llu corrtuped mirrors=", entry->logical);
 		/* Open coded bitmap print. */
@@ -224,7 +271,14 @@ static void report_corrupted_blocks(void)
 				has_printed=true;
 			}
 		}
-		pr_verbose(LOG_DEFAULT, "\n");
+		pr_verbose(LOG_DEFAULT, " affected files:\n");
+		ret = iterate_inodes_from_logical(entry->logical, fs_info, &path,
+						  print_filenames, fs_info);
+		if (ret < 0) {
+			errno = -ret;
+			error("failed to iterate involved files: %m");
+			break;
+		}
 	}
 }
 
@@ -280,7 +334,7 @@ int btrfs_recover_fix_data_checksum(const char *path, enum btrfs_fix_data_checks
 		errno = -ret;
 		error("failed to iterate csum tree: %m");
 	}
-	report_corrupted_blocks();
+	report_corrupted_blocks(fs_info);
 out_close:
 	free_corrupted_blocks();
 	close_ctree_fs_info(fs_info);