2 files changed, 10 insertions, 0 deletions

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 3715feb8446d..d055b1914c3d 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -263,6 +263,10 @@ retry:
                 printk("Please append a correct \"root=\" boot option; here are the available partitions:\n");
 
                 printk_all_partitions();
+#ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
+                printk("DEBUG_BLOCK_EXT_DEVT is enabled, you need to specify "
+                       "explicit textual name for \"root=\" boot option.\n");
+#endif
                 panic("VFS: Unable to mount root fs on %s", b);
         }
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 4378d5e923ca..c556896abe57 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -638,6 +638,12 @@ config DEBUG_BLOCK_EXT_DEVT
           userland code paths which assume predetermined contiguous
           device number allocation.
 
+          Note that turning on this debug option shuffles all the
+          device numbers for all IDE and SCSI devices including libata
+          ones, so root partition specified using device number
+          directly (via rdev or root=MAJ:MIN) won't work anymore.
+          Textual device names (root=/dev/sdXn) will continue to work.
+
           Say N if you are unsure.
 
 config LKDTM