mtd: warn when registering the same master many times

When CONFIG_MTD_PARTITIONED_MASTER=y, it is fatal to call
mtd_device_parse_register() twice on the same MTD, as we try to register
the same device/kobject multipile times.

When CONFIG_MTD_PARTITIONED_MASTER=n, calling
mtd_device_parse_register() is more of just a nuisance, as we can mostly
navigate around any conflicting actions.

But anyway, doing so is a Bad Thing (TM), and we should complain loudly
for any drivers that try to do this.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Reviewed-by: Richard Weinberger <richard@nod.at>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index a2e76ac9f1dc..41dc501cb49a 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -387,6 +387,14 @@ int add_mtd_device(struct mtd_info *mtd)
         struct mtd_notifier *not;
         int i, error;
 
+        /*
+         * May occur, for instance, on buggy drivers which call
+         * mtd_device_parse_register() multiple times on the same master MTD,
+         * especially with CONFIG_MTD_PARTITIONED_MASTER=y.
+         */
+        if (WARN_ONCE(mtd->backing_dev_info, "MTD already registered\n"))
+                return -EEXIST;
+
         mtd->backing_dev_info = &mtd_bdi;
 
         BUG_ON(mtd->writesize == 0);
@@ -606,6 +614,7 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
          * does cause problems with parse_mtd_partitions() above (e.g.,
          * cmdlineparts will register partitions more than once).
          */
+        WARN_ONCE(mtd->reboot_notifier.notifier_call, "MTD already registered\n");
         if (mtd->_reboot && !mtd->reboot_notifier.notifier_call) {
                 mtd->reboot_notifier.notifier_call = mtd_reboot_notifier;
                 register_reboot_notifier(&mtd->reboot_notifier);