btrfs: add reconfigure callback for fs_context

This is what is used to remount the file system with the new mount API.
Because the mount options are parsed separately and one at a time I've
added a helper to emit the mount options after the fact once the mount
is configured, this matches the dmesg output for what happens with the
old mount API.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/zoned.c

@@ -781,7 +781,7 @@ int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
 	 * Check mount options here, because we might change fs_info->zoned
 	 * from fs_info->zone_size.
 	 */
-	ret = btrfs_check_mountopts_zoned(fs_info);
+	ret = btrfs_check_mountopts_zoned(fs_info, &fs_info->mount_opt);
 	if (ret)
 		return ret;
 
@@ -789,7 +789,7 @@ int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
 	return 0;
 }
 
-int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
+int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info, unsigned long *mount_opt)
 {
 	if (!btrfs_is_zoned(info))
 		return 0;
@@ -798,18 +798,21 @@ int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
 	 * Space cache writing is not COWed. Disable that to avoid write errors
 	 * in sequential zones.
 	 */
-	if (btrfs_test_opt(info, SPACE_CACHE)) {
+	if (btrfs_raw_test_opt(*mount_opt, SPACE_CACHE)) {
 		btrfs_err(info, "zoned: space cache v1 is not supported");
 		return -EINVAL;
 	}
 
-	if (btrfs_test_opt(info, NODATACOW)) {
+	if (btrfs_raw_test_opt(*mount_opt, NODATACOW)) {
 		btrfs_err(info, "zoned: NODATACOW not supported");
 		return -EINVAL;
 	}
 
-	btrfs_clear_and_info(info, DISCARD_ASYNC,
-			"zoned: async discard ignored and disabled for zoned mode");
+	if (btrfs_raw_test_opt(*mount_opt, DISCARD_ASYNC)) {
+		btrfs_info(info,
+			   "zoned: async discard ignored and disabled for zoned mode");
+		btrfs_clear_opt(*mount_opt, DISCARD_ASYNC);
+	}
 
 	return 0;
 }

fs/btrfs/zoned.h

@@ -45,7 +45,7 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache);
 void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
 struct btrfs_zoned_device_info *btrfs_clone_dev_zone_info(struct btrfs_device *orig_dev);
 int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info);
-int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info);
+int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info, unsigned long *mount_opt);
 int btrfs_sb_log_location_bdev(struct block_device *bdev, int mirror, int rw,
 			       u64 *bytenr_ret);
 int btrfs_sb_log_location(struct btrfs_device *device, int mirror, int rw,
@@ -121,7 +121,8 @@ static inline int btrfs_check_zoned_mode(const struct btrfs_fs_info *fs_info)
 	return -EOPNOTSUPP;
 }
 
-static inline int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
+static inline int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info,
+					      unsigned long *mount_opt)
 {
 	return 0;
 }