I suspect I could do a better job of showing the original component
size, so that you have a chance of recovering even then.

But the patch:

diff --git a/Grow.c b/Grow.c
index 455c5f9..701590f 100755
--- a/Grow.c
+++ b/Grow.c

@@ -1561,7 +1561,7 @@ static int reshape_container(char *container, char *devname,
 			     char *backup_file, int verbose,
 			     int forked, int restart, int freeze_reshape);
 
-int Grow_reshape(char *devname, int fd,
+int Grow_reshape(char *devname, int fd, int force,
 		 struct mddev_dev *devlist,
 		 unsigned long long data_offset,
 		 struct context *c, struct shape *s)

@@ -1574,6 +1574,7 @@ int Grow_reshape(char *devname, int fd,
 	 * requested everything (if kernel supports freezing - 2.6.30).
 	 * The steps are:
 	 *  - change size (i.e. component_size)
+         *    - when shrinking, you must force the change 
 	 *  - change level
 	 *  - change layout/chunksize/ndisks
 	 *

@@ -1617,6 +1618,11 @@ int Grow_reshape(char *devname, int fd,
 		return 1;
 	}
 
+	if ((s->size < (unsigned)array.size) && !force) {
+	    pr_err("Cannot set device size smaller than current component_size of %s array.  Use -f to force change.\n",devname);
+	    return 1;
+	}
+
 	if (s->raiddisks && s->raiddisks < array.raid_disks && array.level > 1 &&
 	    get_linux_version() < 2006032 &&
 	    !check_env("MDADM_FORCE_FEWER")) {

diff --git a/ReadMe.c b/ReadMe.c
index 50d3807..46988ae 100644
--- a/ReadMe.c
+++ b/ReadMe.c

@@ -203,6 +203,7 @@ struct option long_options[] = {
     {"invalid-backup",0,0,InvalidBackup},
     {"array-size", 1, 0, 'Z'},
     {"continue", 0, 0, Continue},
+    {"force",	  0, 0, Force},
 
     /* For Incremental */
     {"rebuild-map", 0, 0, RebuildMapOpt},

@@ -563,6 +564,7 @@ char Help_grow[] =
 "                      : This is useful if all devices have been replaced\n"
 "                      : with larger devices.   Value is in Kilobytes, or\n"
 "                      : the special word 'max' meaning 'as large as possible'.\n"
+"  --force       -f    : Override normal checks and be more forceful\n"
 "  --assume-clean      : When increasing the --size, this flag will avoid\n"
 "                      : a resync of the new space\n"
 "  --chunk=       -c   : Change the chunksize of the array\n"

diff --git a/mdadm.c b/mdadm.c
index c3a265b..821658a 100644
--- a/mdadm.c
+++ b/mdadm.c

@@ -1617,7 +1617,7 @@ int main(int argc, char *argv[])
 		else if (s.size > 0 || s.raiddisks || s.layout_str ||
 			 s.chunk != 0 || s.level != UnSet ||
 			 data_offset != INVALID_SECTORS) {
-			rv = Grow_reshape(devlist->devname, mdfd,
+		    rv = Grow_reshape(devlist->devname, mdfd, c.force,
 					  devlist->next,
 					  data_offset, &c, &s);
 		} else if (array_size == 0)

diff --git a/mdadm.h b/mdadm.h
index 71b8afb..9e00f05 100644
--- a/mdadm.h
+++ b/mdadm.h

@@ -1300,7 +1300,7 @@ extern int autodetect(void);
 extern int Grow_Add_device(char *devname, int fd, char *newdev);
 extern int Grow_addbitmap(char *devname, int fd,
 			  struct context *c, struct shape *s);
-extern int Grow_reshape(char *devname, int fd,
+extern int Grow_reshape(char *devname, int fd, int force,
 			struct mddev_dev *devlist,
 			unsigned long long data_offset,
 			struct context *c, struct shape *s);
--

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