Index: share/man/man9/disk.9
===================================================================
--- share/man/man9/disk.9
+++ share/man/man9/disk.9
@@ -37,6 +37,8 @@
 .In geom/geom_disk.h
 .Ft struct disk *
 .Fn disk_alloc void
+.Ft struct disk *
+.Fn disk_alloc_nowait void
 .Ft void
 .Fn disk_create "struct disk *disk" "int version"
 .Ft void
@@ -67,12 +69,16 @@
 .Pp
 GEOM has the ownership of
 .Vt "struct disk" ,
-and drivers must allocate storage for it with the
+and drivers must allocate storage for it with one of the
 .Fn disk_alloc
-function,
+or
+.Fn disk_alloc_nowait
+functions,
 fill in the fields and call
 .Fn disk_create
 when the device is ready to service requests.
+.Fn disk_alloc_nowait
+must be used from contexts that cannot sleep.
 .Fn disk_free
 frees uninitialized disks from
 .Fn disk_alloc
Index: sys/geom/geom_disk.h
===================================================================
--- sys/geom/geom_disk.h
+++ sys/geom/geom_disk.h
@@ -137,6 +137,7 @@
 #define	DISKFLAG_WRITE_PROTECT		0x0100
 
 struct disk *disk_alloc(void);
+struct disk *disk_alloc_nowait(void);
 void disk_create(struct disk *disk, int version);
 void disk_destroy(struct disk *disk);
 void disk_free(struct disk *disk);
Index: sys/geom/geom_disk.c
===================================================================
--- sys/geom/geom_disk.c
+++ sys/geom/geom_disk.c
@@ -862,16 +862,30 @@
 	strlcpy(ident, newid, size);
 }
 
-struct disk *
-disk_alloc(void)
+static struct disk *
+disk_alloc_flags(int flags)
 {
 	struct disk *dp;
 
-	dp = g_malloc(sizeof(struct disk), M_WAITOK | M_ZERO);
+	dp = g_malloc(sizeof(struct disk), flags | M_ZERO);
+	if (dp == NULL)
+		return (NULL);
 	LIST_INIT(&dp->d_aliases);
 	return (dp);
 }
 
+struct disk *
+disk_alloc(void)
+{
+	return (disk_alloc_flags(M_WAITOK));
+}
+
+struct disk *
+disk_alloc_nowait(void)
+{
+	return (disk_alloc_flags(M_NOWAIT));
+}
+
 void
 disk_create(struct disk *dp, int version)
 {