--- a/fs/btrfs/ioctl.c	2013-10-21 16:09:48.844287259 -0400
+++ b/fs/btrfs/ioctl.c	2013-10-21 16:10:01.856001602 -0400
@@ -57,6 +57,7 @@
 #include "rcu-string.h"
 #include "send.h"
 #include "dev-replace.h"
+#include "sysfs.h"
 
 static int btrfs_clone(struct inode *src, struct inode *inode,
 		       u64 off, u64 olen, u64 olen_aligned, u64 destoff);
@@ -4531,17 +4532,27 @@ static int btrfs_ioctl_get_features(stru
 	return 0;
 }
 
-static int check_feature_bits(struct btrfs_root *root, const char *type,
+static int check_feature_bits(struct btrfs_root *root,
+			      enum btrfs_feature_set set,
 			      u64 change_mask, u64 flags, u64 supported_flags,
 			      u64 safe_set, u64 safe_clear)
 {
+	const char *type = btrfs_feature_set_names[set];
+	char *names;
 	u64 disallowed, unsupported;
 	u64 set_mask = flags & change_mask;
 	u64 clear_mask = ~flags & change_mask;
 
 	unsupported = set_mask & ~supported_flags;
 	if (unsupported) {
-		btrfs_warn(root->fs_info,
+		names = btrfs_printable_features(set, unsupported);
+		if (names) {
+			btrfs_warn(root->fs_info,
+			   "this kernel does not support the %s feature bit%s",
+			   names, strchr(names, ',') ? "s" : "");
+			kfree(names);
+		} else
+			btrfs_warn(root->fs_info,
 			   "this kernel does not support %s bits 0x%llx",
 			   type, unsupported);
 		return -EOPNOTSUPP;
@@ -4549,7 +4560,14 @@ static int check_feature_bits(struct btr
 
 	disallowed = set_mask & ~safe_set;
 	if (disallowed) {
-		btrfs_warn(root->fs_info,
+		names = btrfs_printable_features(set, disallowed);
+		if (names) {
+			btrfs_warn(root->fs_info,
+			   "can't set the %s feature bit%s while mounted",
+			   names, strchr(names, ',') ? "s" : "");
+			kfree(names);
+		} else
+			btrfs_warn(root->fs_info,
 			   "can't set %s bits 0x%llx while mounted",
 			   type, disallowed);
 		return -EPERM;
@@ -4557,7 +4575,14 @@ static int check_feature_bits(struct btr
 
 	disallowed = clear_mask & ~safe_clear;
 	if (disallowed) {
-		btrfs_warn(root->fs_info,
+		names = btrfs_printable_features(set, disallowed);
+		if (names) {
+			btrfs_warn(root->fs_info,
+			   "can't clear the %s feature bit%s while mounted",
+			   names, strchr(names, ',') ? "s" : "");
+			kfree(names);
+		} else
+			btrfs_warn(root->fs_info,
 			   "can't clear %s bits 0x%llx while mounted",
 			   type, disallowed);
 		return -EPERM;
@@ -4567,7 +4592,7 @@ static int check_feature_bits(struct btr
 }
 
 #define check_feature(root, change_mask, flags, mask_base)	\
-check_feature_bits(root, # mask_base, change_mask, flags,	\
+check_feature_bits(root, FEAT_##mask_base, change_mask, flags,	\
 		   BTRFS_FEATURE_ ## mask_base ## _SUPP,	\
 		   BTRFS_FEATURE_ ## mask_base ## _SAFE_SET,	\
 		   BTRFS_FEATURE_ ## mask_base ## _SAFE_CLEAR)
--- a/fs/btrfs/sysfs.c	2013-10-21 16:10:01.456010390 -0400
+++ b/fs/btrfs/sysfs.c	2013-10-21 16:10:01.856001602 -0400
@@ -254,6 +254,31 @@ const char * const btrfs_feature_set_nam
 static char btrfs_unknown_feature_names[3][NUM_FEATURE_BITS][13];
 static struct btrfs_feature_attr btrfs_feature_attrs[3][NUM_FEATURE_BITS];
 
+char *btrfs_printable_features(enum btrfs_feature_set set, u64 flags)
+{
+	size_t bufsize = 4096; /* safe max, 64 names * 64 bytes */
+	int len = 0;
+	int i;
+	char *str;
+
+	str = kmalloc(bufsize, GFP_KERNEL);
+	if (!str)
+		return str;
+
+	for (i = 0; i < ARRAY_SIZE(btrfs_feature_attrs[set]); i++) {
+		const char *name;
+
+		if (!(flags & (1ULL << i)))
+			continue;
+
+		name = btrfs_feature_attrs[set][i].kobj_attr.attr.name;
+		len += snprintf(str + len, bufsize - len, "%s%s",
+				len ? "," : "", name);
+	}
+
+	return str;
+}
+
 static void init_feature_attrs(void)
 {
 	struct btrfs_feature_attr *fa;
@@ -264,11 +289,17 @@ static void init_feature_attrs(void)
 	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names[0]) !=
 		     ARRAY_SIZE(btrfs_feature_attrs[0]));
 
+	memset(btrfs_feature_attrs, 0, sizeof(btrfs_feature_attrs));
+	memset(btrfs_unknown_feature_names, 0,
+	       sizeof(btrfs_unknown_feature_names));
+
 	for (i = 0; btrfs_supported_feature_attrs[i]; i++) {
 		struct btrfs_feature_attr *sfa;
 		struct attribute *a = btrfs_supported_feature_attrs[i];
+		int bit;
 		sfa = attr_to_btrfs_feature_attr(a);
-		fa = &btrfs_feature_attrs[sfa->feature_set][sfa->feature_bit];
+		bit = ilog2(sfa->feature_bit);
+		fa = &btrfs_feature_attrs[sfa->feature_set][bit];
 
 		fa->kobj_attr.attr.name = sfa->kobj_attr.attr.name;
 	}
--- a/fs/btrfs/sysfs.h	2013-10-21 16:10:01.460010303 -0400
+++ b/fs/btrfs/sysfs.h	2013-10-21 16:10:01.860001514 -0400
@@ -51,4 +51,6 @@ static struct btrfs_feature_attr btrfs_a
 #define attr_to_btrfs_attr(a) container_of(a, struct kobj_attribute, attr)
 #define attr_to_btrfs_feature_attr(a) \
 			to_btrfs_feature_attr(attr_to_btrfs_attr(a))
+char *btrfs_printable_features(enum btrfs_feature_set set, u64 flags);
+extern const char * const btrfs_feature_set_names[3];
 #endif /* _BTRFS_SYSFS_H_ */
