Index: sys/fs/ext2fs/ext2_vfsops.c
===================================================================
--- sys/fs/ext2fs/ext2_vfsops.c
+++ sys/fs/ext2fs/ext2_vfsops.c
@@ -279,6 +279,7 @@
 static int
 ext2_check_sb_compat(struct ext2fs *es, struct cdev *dev, int ronly)
 {
+	uint32_t i, mask;
 
 	if (es->e2fs_magic != E2FS_MAGIC) {
 		printf("ext2fs: %s: wrong magic number %#x (expected %#x)\n",
@@ -286,17 +287,25 @@
 		return (1);
 	}
 	if (es->e2fs_rev > E2FS_REV0) {
-		if (es->e2fs_features_incompat & ~(EXT2F_INCOMPAT_SUPP |
-						   EXT4F_RO_INCOMPAT_SUPP)) {
-			printf(
-"WARNING: mount of %s denied due to unsupported optional features\n",
-			    devtoname(dev));
+		mask = es->e2fs_features_incompat & ~(EXT2F_INCOMPAT_SUPP |
+		    EXT4F_RO_INCOMPAT_SUPP);
+		if (mask) {
+			printf("WARNING: mount of %s denied due to "
+			    "unsupported optional features:\n", devtoname(dev));
+			for (i = 0; i < nitems(incompat_names); i++)
+				if (mask & incompat_names[i].mask)
+					printf("%s ", incompat_names[i].name);
+			printf("\n");
 			return (1);
 		}
-		if (!ronly &&
-		    (es->e2fs_features_rocompat & ~EXT2F_ROCOMPAT_SUPP)) {
+		mask = es->e2fs_features_rocompat & ~EXT2F_ROCOMPAT_SUPP;
+		if (!ronly && mask) {
 			printf("WARNING: R/W mount of %s denied due to "
-			    "unsupported optional features\n", devtoname(dev));
+			    "unsupported optional features:\n", devtoname(dev));
+			for (i = 0; i < nitems(ro_compat_names); i++)
+				if (mask & ro_compat_names[i].mask)
+					printf("%s ", ro_compat_names[i].name);
+			printf("\n");
 			return (1);
 		}
 	}
Index: sys/fs/ext2fs/ext2fs.h
===================================================================
--- sys/fs/ext2fs/ext2fs.h
+++ sys/fs/ext2fs/ext2fs.h
@@ -202,40 +202,104 @@
 /*
  * compatible/incompatible features
  */
-#define	EXT2F_COMPAT_PREALLOC		0x0001
-#define	EXT2F_COMPAT_HASJOURNAL		0x0004
-#define	EXT2F_COMPAT_EXT_ATTR		0x0008
-#define	EXT2F_COMPAT_RESIZE		0x0010
-#define	EXT2F_COMPAT_DIRHASHINDEX	0x0020
-#define	EXT2F_COMPAT_SPARSESUPER2	0x0200
-
-#define	EXT2F_ROCOMPAT_SPARSESUPER	0x0001
-#define	EXT2F_ROCOMPAT_LARGEFILE	0x0002
-#define	EXT2F_ROCOMPAT_BTREE_DIR	0x0004
-#define	EXT2F_ROCOMPAT_HUGE_FILE	0x0008
-#define	EXT2F_ROCOMPAT_GDT_CSUM		0x0010
-#define	EXT2F_ROCOMPAT_DIR_NLINK	0x0020
-#define	EXT2F_ROCOMPAT_EXTRA_ISIZE	0x0040
-#define	EXT2F_ROCOMPAT_QUOTA		0x0100
-#define	EXT2F_ROCOMPAT_BIGALLOC		0x0200
-#define	EXT2F_ROCOMPAT_METADATA_CKSUM	0x0400
-#define	EXT2F_ROCOMPAT_READONLY		0x1000
-#define	EXT2F_ROCOMPAT_PROJECT		0x2000
-
-#define	EXT2F_INCOMPAT_COMP		0x0001
-#define	EXT2F_INCOMPAT_FTYPE		0x0002
-#define	EXT2F_INCOMPAT_RECOVER		0x0004
-#define	EXT2F_INCOMPAT_META_BG		0x0010
-#define	EXT2F_INCOMPAT_EXTENTS		0x0040
-#define	EXT2F_INCOMPAT_64BIT		0x0080
-#define	EXT2F_INCOMPAT_MMP		0x0100
-#define	EXT2F_INCOMPAT_FLEX_BG		0x0200
-#define	EXT2F_INCOMPAT_EA_INODE		0x0400
-#define	EXT2F_INCOMPAT_DIRDATA		0x1000
-#define	EXT2F_INCOMPAT_CSUM_SEED	0x2000
-#define	EXT2F_INCOMPAT_LARGEDIR		0x4000
-#define	EXT2F_INCOMPAT_INLINE_DATA	0x8000
-#define	EXT2F_INCOMPAT_ENCRYPT		0x10000
+typedef enum {
+	EXT2F_COMPAT_PREALLOC		= 0x0001,
+	EXT2F_COMPAT_IMAGIC_INODES	= 0x0002,
+	EXT2F_COMPAT_HASJOURNAL		= 0x0004,
+	EXT2F_COMPAT_EXT_ATTR		= 0x0008,
+	EXT2F_COMPAT_RESIZE		= 0x0010,
+	EXT2F_COMPAT_DIRHASHINDEX	= 0x0020,
+	EXT2F_COMPAT_LAZY_BG		= 0x0040,
+	EXT2F_COMPAT_EXCLUDE_BITMAP	= 0x0100,
+	EXT2F_COMPAT_SPARSESUPER2	= 0x0200
+} compat;
+
+typedef enum {
+	EXT2F_ROCOMPAT_SPARSESUPER	= 0x0001,
+	EXT2F_ROCOMPAT_LARGEFILE	= 0x0002,
+	EXT2F_ROCOMPAT_BTREE_DIR	= 0x0004,
+	EXT2F_ROCOMPAT_HUGE_FILE	= 0x0008,
+	EXT2F_ROCOMPAT_GDT_CSUM		= 0x0010,
+	EXT2F_ROCOMPAT_DIR_NLINK	= 0x0020,
+	EXT2F_ROCOMPAT_EXTRA_ISIZE	= 0x0040,
+	EXT2F_ROCOMPAT_HAS_SNAPSHOT	= 0x0080,
+	EXT2F_ROCOMPAT_QUOTA		= 0x0100,
+	EXT2F_ROCOMPAT_BIGALLOC		= 0x0200,
+	EXT2F_ROCOMPAT_METADATA_CKSUM	= 0x0400,
+	EXT2F_ROCOMPAT_REPLICA		= 0x0800,
+	EXT2F_ROCOMPAT_READONLY		= 0x1000,
+	EXT2F_ROCOMPAT_PROJECT		= 0x2000
+} ro_compat;
+
+typedef enum {
+	EXT2F_INCOMPAT_COMP		= 0x0001,
+	EXT2F_INCOMPAT_FTYPE		= 0x0002,
+	EXT2F_INCOMPAT_RECOVER		= 0x0004,
+	EXT2F_INCOMPAT_JOURNAL_DEV	= 0x0008,
+	EXT2F_INCOMPAT_META_BG		= 0x0010,
+	EXT2F_INCOMPAT_EXTENTS		= 0x0040,
+	EXT2F_INCOMPAT_64BIT		= 0x0080,
+	EXT2F_INCOMPAT_MMP		= 0x0100,
+	EXT2F_INCOMPAT_FLEX_BG		= 0x0200,
+	EXT2F_INCOMPAT_EA_INODE		= 0x0400,
+	EXT2F_INCOMPAT_DIRDATA		= 0x1000,
+	EXT2F_INCOMPAT_CSUM_SEED	= 0x2000,
+	EXT2F_INCOMPAT_LARGEDIR		= 0x4000,
+	EXT2F_INCOMPAT_INLINE_DATA	= 0x8000,
+	EXT2F_INCOMPAT_ENCRYPT		= 0x10000
+} incompat;
+
+struct ext2_feature
+{
+	int mask;
+	const char *name;
+};
+
+static const struct ext2_feature compat_names[] = {
+	{ EXT2F_COMPAT_PREALLOC,       "dir_prealloc"    },
+	{ EXT2F_COMPAT_IMAGIC_INODES,  "imagic_inodes"   },
+	{ EXT2F_COMPAT_HASJOURNAL,     "has_journal"     },
+	{ EXT2F_COMPAT_EXT_ATTR,       "ext_attr"        },
+	{ EXT2F_COMPAT_RESIZE,         "resize_inode"    },
+	{ EXT2F_COMPAT_DIRHASHINDEX,   "dir_index"       },
+	{ EXT2F_COMPAT_EXCLUDE_BITMAP, "snapshot_bitmap" },
+	{ EXT2F_COMPAT_SPARSESUPER2,   "sparse_super2"   }
+};
+
+static const struct ext2_feature ro_compat_names[] = {
+	{ EXT2F_ROCOMPAT_SPARSESUPER,    "sparse_super"  },
+	{ EXT2F_ROCOMPAT_LARGEFILE,      "large_file"    },
+	{ EXT2F_ROCOMPAT_BTREE_DIR,      "btree_dir"     },
+	{ EXT2F_ROCOMPAT_HUGE_FILE,      "huge_file"     },
+	{ EXT2F_ROCOMPAT_GDT_CSUM,       "uninit_groups" },
+	{ EXT2F_ROCOMPAT_DIR_NLINK,      "dir_nlink"     },
+	{ EXT2F_ROCOMPAT_EXTRA_ISIZE,    "extra_isize"   },
+	{ EXT2F_ROCOMPAT_HAS_SNAPSHOT,   "snapshot"      },
+	{ EXT2F_ROCOMPAT_QUOTA,          "quota"         },
+	{ EXT2F_ROCOMPAT_BIGALLOC,       "bigalloc"      },
+	{ EXT2F_ROCOMPAT_METADATA_CKSUM, "metadata_csum" },
+	{ EXT2F_ROCOMPAT_REPLICA,        "replica"       },
+	{ EXT2F_ROCOMPAT_READONLY,       "ro"            },
+	{ EXT2F_ROCOMPAT_PROJECT,        "project"       }
+};
+
+static const struct ext2_feature incompat_names[] = {
+	{ EXT2F_INCOMPAT_COMP,        "compression"        },
+	{ EXT2F_INCOMPAT_FTYPE,       "filetype"           },
+	{ EXT2F_INCOMPAT_RECOVER,     "needs_recovery"     },
+	{ EXT2F_INCOMPAT_JOURNAL_DEV, "journal_dev"        },
+	{ EXT2F_INCOMPAT_META_BG,     "meta_bg"            },
+	{ EXT2F_INCOMPAT_EXTENTS,     "extents"            },
+	{ EXT2F_INCOMPAT_64BIT,       "64bit"              },
+	{ EXT2F_INCOMPAT_MMP,         "mmp"                },
+	{ EXT2F_INCOMPAT_FLEX_BG,     "flex_bg"            },
+	{ EXT2F_INCOMPAT_EA_INODE,    "ea_inode"           },
+	{ EXT2F_INCOMPAT_DIRDATA,     "dirdata"            },
+	{ EXT2F_INCOMPAT_CSUM_SEED,   "metadata_csum_seed" },
+	{ EXT2F_INCOMPAT_LARGEDIR,    "large_dir"          },
+	{ EXT2F_INCOMPAT_INLINE_DATA, "inline_data"        },
+	{ EXT2F_INCOMPAT_ENCRYPT,     "encrypt"            }
+};
 
 /*
  * Features supported in this implementation