btrfs-progs: fix-data-checksum: update csum items to fix csum mismatch

Add a new group of actions in the interactive mode to fix a csum
mismatch.

The output looks like this:

  logical=13631488 corrtuped mirrors=1 affected files:
    (subvolume 5)/foo
    (subvolume 5)/dir/bar
  <<I>>gnore/<1>:1
  Csum item for logical 13631488 updated using data from mirror 1

In the interactive mode, the update-csum-item behavior is printed as all
available mirror numbers.

Considering all the existing (and future) actions, the name should start
with an single letter, it's pretty easy to distinguish mirror number
from other actions.

The update-csum-item action itself is pretty straight-forward, just read
out the data from specified mirror, then calculate a new checksum, and
update the corresponding csum item in csum tree.

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

Author: adam900710

cmds/rescue-fix-data-checksum.c

@@ -20,6 +20,8 @@
 #include "kernel-shared/ctree.h"
 #include "kernel-shared/volumes.h"
 #include "kernel-shared/backref.h"
+#include "kernel-shared/transaction.h"
+#include "kernel-shared/file-item.h"
 #include "common/messages.h"
 #include "common/open-utils.h"
 #include "cmds/rescue.h"
@@ -48,6 +50,7 @@ struct corrupted_block {
 
 enum fix_data_checksum_action_value {
 	ACTION_IGNORE,
+	ACTION_UPDATE_CSUM,
 	ACTION_LAST,
 };
 
@@ -59,6 +62,10 @@ static const struct fix_data_checksum_action {
 		.value = ACTION_IGNORE,
 		.string = "ignore"
 	},
+	[ACTION_UPDATE_CSUM] = {
+		.value = ACTION_UPDATE_CSUM,
+		.string = "update-csum"
+	},
 };
 
 static int global_repair_mode;
@@ -260,23 +267,35 @@ static int iterate_csum_root(struct btrfs_fs_info *fs_info, struct btrfs_root *c
 }
 
 #define ASK_ACTION_BUFSIZE	(32)
-static enum fix_data_checksum_action_value ask_action(void)
+static enum fix_data_checksum_action_value ask_action(unsigned int num_mirrors,
+						      unsigned int *mirror_ret)
 {
+	unsigned long ret;
 	char buf[ASK_ACTION_BUFSIZE] = { 0 };
 	bool printed;
+	char *endptr;
 
 again:
 	printed = false;
 	for (int i = 0; i < ACTION_LAST; i++) {
 		if (printed)
 			pr_verbose(LOG_DEFAULT, "/");
 		/* Mark Ignore as default. */
-		if (i == ACTION_IGNORE)
+		if (i == ACTION_IGNORE) {
 			pr_verbose(LOG_DEFAULT, "<<%c>>%s", toupper(actions[i].string[0]),
 				   actions[i].string + 1);
-		else
+		} else if (i == ACTION_UPDATE_CSUM) {
+			/*
+			 * For update-csum action, we need a mirror number,
+			 * so output all valid mirrors numbers instead.
+			 */
+			for (int cur_mirror = 1; cur_mirror <= num_mirrors; cur_mirror++)
+				pr_verbose(LOG_DEFAULT, "<%u>", cur_mirror);
+		} else {
 			pr_verbose(LOG_DEFAULT, "<%c>%s", toupper(actions[i].string[0]),
 				   actions[i].string + 1);
+		}
+		printed = true;
 	}
 	pr_verbose(LOG_DEFAULT, ":");
 	fflush(stdout);
@@ -287,13 +306,79 @@ static enum fix_data_checksum_action_value ask_action(void)
 		return ACTION_IGNORE;
 	/* Check exact match or matching the initial letter. */
 	for (int i = 0; i < ACTION_LAST; i++) {
-		if (strncasecmp(buf, actions[i].string, 1) == 0 ||
-		    strncasecmp(buf, actions[i].string, ASK_ACTION_BUFSIZE) == 0)
+		if ((strncasecmp(buf, actions[i].string, 1) == 0 ||
+		     strncasecmp(buf, actions[i].string, ASK_ACTION_BUFSIZE) == 0) &&
+		     actions[i].value != ACTION_UPDATE_CSUM)
 			return actions[i].value;
 	}
-	/* No valid action found, retry. */
-	warning("invalid action, please retry");
-	goto again;
+	/* No match, check if it's some numeric string. */
+	ret = strtoul(buf, &endptr, 10);
+	if (endptr == buf || ret == ULONG_MAX) {
+		/* No valid action found, retry. */
+		warning("invalid action, please retry");
+		goto again;
+	}
+	if (ret > num_mirrors || ret == 0) {
+		warning("invalid mirror number %lu, must be in range [1, %d], please retry",
+			ret, num_mirrors);
+		goto again;
+	}
+	*mirror_ret = ret;
+	return ACTION_UPDATE_CSUM;
+}
+
+static int update_csum_item(struct btrfs_fs_info *fs_info, u64 logical,
+			    unsigned int mirror)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *csum_root = btrfs_csum_root(fs_info, logical);
+	struct btrfs_path path = { 0 };
+	struct btrfs_csum_item *citem;
+	u64 read_len = fs_info->sectorsize;
+	u8 csum[BTRFS_CSUM_SIZE] = { 0 };
+	u8 *buf;
+	int ret;
+
+	buf = malloc(fs_info->sectorsize);
+	if (!buf)
+		return -ENOMEM;
+	ret = read_data_from_disk(fs_info, buf, logical, &read_len, mirror);
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to read block at logical %llu mirror %u: %m",
+			logical, mirror);
+		goto out;
+	}
+	trans = btrfs_start_transaction(csum_root, 1);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		errno = -ret;
+		error_msg(ERROR_MSG_START_TRANS, "%m");
+		goto out;
+	}
+	citem = btrfs_lookup_csum(trans, csum_root, &path, logical,
+				  BTRFS_EXTENT_CSUM_OBJECTID, fs_info->csum_type, 1);
+	if (IS_ERR(citem)) {
+		ret = PTR_ERR(citem);
+		errno = -ret;
+		error("failed to find csum item for logical %llu: $m", logical);
+		btrfs_abort_transaction(trans, ret);
+		goto out;
+	}
+	btrfs_csum_data(fs_info, fs_info->csum_type, buf, csum, fs_info->sectorsize);
+	write_extent_buffer(path.nodes[0], csum, (unsigned long)citem, fs_info->csum_size);
+	btrfs_release_path(&path);
+	ret = btrfs_commit_transaction(trans, csum_root);
+	if (ret < 0) {
+		errno = -ret;
+		error_msg(ERROR_MSG_COMMIT_TRANS, "%m");
+	}
+	printf("Csum item for logical %llu updated using data from mirror %u\n",
+		logical, mirror);
+out:
+	free(buf);
+	btrfs_release_path(&path);
+	return ret;
 }
 
 static void report_corrupted_blocks(struct btrfs_fs_info *fs_info,
@@ -309,6 +394,7 @@ static void report_corrupted_blocks(struct btrfs_fs_info *fs_info,
 	}
 
 	list_for_each_entry(entry, &corrupted_blocks, list) {
+		unsigned int mirror;
 		bool has_printed = false;
 		int ret;
 
@@ -336,10 +422,20 @@ static void report_corrupted_blocks(struct btrfs_fs_info *fs_info,
 		}
 		switch (mode) {
 		case BTRFS_FIX_DATA_CSUMS_INTERACTIVE:
-			action = ask_action();
-			UASSERT(action == ACTION_IGNORE);
-			fallthrough;
+			action = ask_action(entry->num_mirrors, &mirror);
+			break;
 		case BTRFS_FIX_DATA_CSUMS_READONLY:
+			action = ACTION_IGNORE;
+			break;
+		default:
+			UASSERT(0);
+		}
+
+		switch (action) {
+		case ACTION_IGNORE:
+			break;
+		case ACTION_UPDATE_CSUM:
+			ret = update_csum_item(fs_info, entry->logical, mirror);
 			break;
 		default:
 			UASSERT(0);

kernel-shared/file-item.c

@@ -112,7 +112,7 @@ int btrfs_insert_inline_extent(struct btrfs_trans_handle *trans,
 	return err;
 }
 
-static struct btrfs_csum_item *
+struct btrfs_csum_item *
 btrfs_lookup_csum(struct btrfs_trans_handle *trans,
 		  struct btrfs_root *root,
 		  struct btrfs_path *path,

kernel-shared/file-item.h

@@ -89,6 +89,11 @@ int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_file_extent_item *stack_fi);
 int btrfs_csum_file_block(struct btrfs_trans_handle *trans, u64 logical,
 			  u64 csum_objectid, u32 csum_type, const char *data);
+struct btrfs_csum_item *
+btrfs_lookup_csum(struct btrfs_trans_handle *trans,
+		  struct btrfs_root *root,
+		  struct btrfs_path *path,
+		  u64 bytenr, u64 csum_objectid, u16 csum_type, int cow);
 int btrfs_insert_inline_extent(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root, u64 objectid,
 			       u64 offset, const char *buffer, size_t size,