btrfs: add error messages to all unrecognized mount options

Almost none of the errors stemming from a valid mount option but wrong
value prints a descriptive message which would help to identify why
mount failed. Like in the linked report:

  $ uname -r
  v4.19
  $ mount -o compress=zstd /dev/sdb /mnt
  mount: /mnt: wrong fs type, bad option, bad superblock on
  /dev/sdb, missing codepage or helper program, or other error.
  $ dmesg
  ...
  BTRFS error (device sdb): open_ctree failed

Errors caused by memory allocation failures are left out as it's not a
user error so reporting that would be confusing.

Link: https://lore.kernel.org/linux-btrfs/[email protected]/
CC: [email protected] # 4.9+
Reviewed-by: Qu Wenruo <[email protected]>
Reviewed-by: Nikolay Borisov <[email protected]>
Reviewed-by: Anand Jain <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: kdave

fs/btrfs/super.c

@@ -763,6 +763,8 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 				compress_force = false;
 				no_compress++;
 			} else {
+				btrfs_err(info, "unrecognized compression value %s",
+					  args[0].from);
 				ret = -EINVAL;
 				goto out;
 			}
@@ -821,8 +823,11 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 		case Opt_thread_pool:
 			ret = match_int(&args[0], &intarg);
 			if (ret) {
+				btrfs_err(info, "unrecognized thread_pool value %s",
+					  args[0].from);
 				goto out;
 			} else if (intarg == 0) {
+				btrfs_err(info, "invalid value 0 for thread_pool");
 				ret = -EINVAL;
 				goto out;
 			}
@@ -883,8 +888,11 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			break;
 		case Opt_ratio:
 			ret = match_int(&args[0], &intarg);
-			if (ret)
+			if (ret) {
+				btrfs_err(info, "unrecognized metadata_ratio value %s",
+					  args[0].from);
 				goto out;
+			}
 			info->metadata_ratio = intarg;
 			btrfs_info(info, "metadata ratio %u",
 				   info->metadata_ratio);
@@ -901,6 +909,8 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 				btrfs_set_and_info(info, DISCARD_ASYNC,
 						   "turning on async discard");
 			} else {
+				btrfs_err(info, "unrecognized discard mode value %s",
+					  args[0].from);
 				ret = -EINVAL;
 				goto out;
 			}
@@ -933,6 +943,8 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 				btrfs_set_and_info(info, FREE_SPACE_TREE,
 						   "enabling free space tree");
 			} else {
+				btrfs_err(info, "unrecognized space_cache value %s",
+					  args[0].from);
 				ret = -EINVAL;
 				goto out;
 			}
@@ -1014,8 +1026,12 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			break;
 		case Opt_check_integrity_print_mask:
 			ret = match_int(&args[0], &intarg);
-			if (ret)
+			if (ret) {
+				btrfs_err(info,
+				"unrecognized check_integrity_print_mask value %s",
+					args[0].from);
 				goto out;
+			}
 			info->check_integrity_print_mask = intarg;
 			btrfs_info(info, "check_integrity_print_mask 0x%x",
 				   info->check_integrity_print_mask);
@@ -1030,22 +1046,28 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			goto out;
 #endif
 		case Opt_fatal_errors:
-			if (strcmp(args[0].from, "panic") == 0)
+			if (strcmp(args[0].from, "panic") == 0) {
 				btrfs_set_opt(info->mount_opt,
 					      PANIC_ON_FATAL_ERROR);
-			else if (strcmp(args[0].from, "bug") == 0)
+			} else if (strcmp(args[0].from, "bug") == 0) {
 				btrfs_clear_opt(info->mount_opt,
 					      PANIC_ON_FATAL_ERROR);
-			else {
+			} else {
+				btrfs_err(info, "unrecognized fatal_errors value %s",
+					  args[0].from);
 				ret = -EINVAL;
 				goto out;
 			}
 			break;
 		case Opt_commit_interval:
 			intarg = 0;
 			ret = match_int(&args[0], &intarg);
-			if (ret)
+			if (ret) {
+				btrfs_err(info, "unrecognized commit_interval value %s",
+					  args[0].from);
+				ret = -EINVAL;
 				goto out;
+			}
 			if (intarg == 0) {
 				btrfs_info(info,
 					   "using default commit interval %us",
@@ -1059,8 +1081,11 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			break;
 		case Opt_rescue:
 			ret = parse_rescue_options(info, args[0].from);
-			if (ret < 0)
+			if (ret < 0) {
+				btrfs_err(info, "unrecognized rescue value %s",
+					  args[0].from);
 				goto out;
+			}
 			break;
 #ifdef CONFIG_BTRFS_DEBUG
 		case Opt_fragment_all: