mdopen: call "modprobe md_mod" if it might be needed.

Creating an array by opening a block-device with major number of 9
will transparently load the md module if needed.
Creating an array by opening
   /sys/module/md_mod/parameters/new_array
and writing to it won't, it will just fail if md_mod isn't loaded.

So when opening that file fails with ENOENT, run "modprobe md_mod" and
try again.

This fixes a bug whereby if you have "CREATE names=yes" in mdadm.conf,
and the md modules isn't loaded, then creating or assembling an
array will not honor the "names=yes" configuration.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>

diff --git a/mdopen.c b/mdopen.c
index 3c0052f2db23a000362a05e838bd735ee65ccc45..dcdc6f23e6c14176a2278c3d67110545891fd4ee 100644 (file)
--- a/mdopen.c
+++ b/mdopen.c
@@ -312,6 +312,10 @@ int create_mddev(char *dev, char *name, int autof, int trustworthy,
                if (block_udev)
                        udev_block(devnm);
                fd = open("/sys/module/md_mod/parameters/new_array", O_WRONLY);
+               if (fd < 0 && errno == ENOENT) {
+                       system("modprobe md_mod");
+                       fd = open("/sys/module/md_mod/parameters/new_array", O_WRONLY);
+               }
                if (fd >= 0) {
                        n = write(fd, devnm, strlen(devnm));
                        close(fd);