diff --git a/Documentation/btrfs-check.asciidoc b/Documentation/btrfs-check.asciidoc
index fa054e45..fbf48847 100644
--- a/Documentation/btrfs-check.asciidoc
+++ b/Documentation/btrfs-check.asciidoc
@@ -3,7 +3,7 @@ btrfs-check(8)
 
 NAME
 ----
-btrfs-check - check or repair an unmounted btrfs filesystem
+btrfs-check - check or repair a btrfs filesystem
 
 SYNOPSIS
 --------
@@ -13,7 +13,9 @@ DESCRIPTION
 -----------
 
 The filesystem checker is used to verify structural integrity of a filesystem
-and attempt to repair it if requested. The filesystem must be unmounted.
+and attempt to repair it if requested.  It is recommended to unmount the
+filesystem prior to running the check, but it is possible to start checking a
+mounted filesystem (see '--force').
 
 By default, *btrfs check* will not modify the device but you can reaffirm that
 by the option '--readonly'.
@@ -120,6 +122,12 @@ needs to re-read blocks when needed. This may increase run time.
 NOTE: 'lowmem' mode does not work with '--repair' yet, and is still considered
 experimental.
 
+--force::
+allow to work on a mounted filesystem. Note that this should work fine on a
+quiescent or read-only mounted filesystem but may crash if the device is
+changed externally, eg. by the kernel module.  Repair without mount checks is
+not supported right now.
+
 EXIT STATUS
 -----------
 *btrfs check* returns a zero exit status if it succeeds. Non zero is
diff --git a/cmds-check.c b/cmds-check.c
index a633d044..006edbde 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -12730,6 +12730,7 @@ const char * const cmd_check_usage[] = {
 	"",
 	"-s|--super <superblock>     use this superblock copy",
 	"-b|--backup                 use the first valid backup root copy",
+	"--force                     skip mount checks, repair is not possible",
 	"--repair                    try to repair the filesystem",
 	"--readonly                  run in read-only mode (default)",
 	"--init-csum-tree            create a new CRC tree",
@@ -12761,7 +12762,7 @@ int cmd_check(int argc, char **argv)
 	u64 tree_root_bytenr = 0;
 	u64 chunk_root_bytenr = 0;
 	char uuidbuf[BTRFS_UUID_UNPARSED_SIZE];
-	int ret;
+	int ret = 0;
 	int err = 0;
 	u64 num;
 	int init_csum_tree = 0;
@@ -12770,13 +12771,15 @@ int cmd_check(int argc, char **argv)
 	int qgroup_report = 0;
 	int qgroups_repaired = 0;
 	unsigned ctree_flags = OPEN_CTREE_EXCLUSIVE;
+	int force = 0;
 
 	while(1) {
 		int c;
 		enum { GETOPT_VAL_REPAIR = 257, GETOPT_VAL_INIT_CSUM,
 			GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
 			GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
-			GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE };
+			GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE,
+			GETOPT_VAL_FORCE };
 		static const struct option long_options[] = {
 			{ "super", required_argument, NULL, 's' },
 			{ "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
@@ -12798,6 +12801,7 @@ int cmd_check(int argc, char **argv)
 				GETOPT_VAL_MODE },
 			{ "clear-space-cache", required_argument, NULL,
 				GETOPT_VAL_CLEAR_SPACE_CACHE},
+			{ "force", no_argument, NULL, GETOPT_VAL_FORCE },
 			{ NULL, 0, NULL, 0}
 		};
 
@@ -12882,6 +12886,9 @@ int cmd_check(int argc, char **argv)
 				}
 				ctree_flags |= OPEN_CTREE_WRITES;
 				break;
+			case GETOPT_VAL_FORCE:
+				force = 1;
+				break;
 		}
 	}
 
@@ -12910,15 +12917,36 @@ int cmd_check(int argc, char **argv)
 	radix_tree_init();
 	cache_tree_init(&root_cache);
 
-	if((ret = check_mounted(argv[optind])) < 0) {
-		error("could not check mount status: %s", strerror(-ret));
-		err |= !!ret;
-		goto err_out;
-	} else if(ret) {
-		error("%s is currently mounted, aborting", argv[optind]);
-		ret = -EBUSY;
-		err |= !!ret;
-		goto err_out;
+	ret = check_mounted(argv[optind]);
+	if (!force) {
+		if (ret < 0) {
+			error("could not check mount status: %s",
+					strerror(-ret));
+			err |= !!ret;
+			goto err_out;
+		} else if (ret) {
+			error(
+"%s is currently mounted, use --force if you really intend to check the filesystem",
+				argv[optind]);
+			ret = -EBUSY;
+			err |= !!ret;
+			goto err_out;
+		}
+	} else {
+		if (repair) {
+			error("repair and --force is not yet supported");
+			ret = 1;
+			err |= !!ret;
+			goto err_out;
+		}
+		if (ret < 0) {
+			warning(
+"cannot check mount status of %s, the filesystem could be mounted, continuing because of --force",
+				argv[optind]);
+		} else if (ret) {
+			warning(
+			"filesystem mounted, continuing because of --force");
+		}
 	}
 
 	/* only allow partial opening under repair mode */