Commit 264725e3 authored Jul 31, 2023 by Miquel Raynal

mtd: Clean refcounting with MTD_PARTITIONED_MASTER



The logic is way too convoluted, let's clean the kref_get/put section to
clarify what this block does when using CONFIG_MTD_PARTITIONED_MASTER:
- Iterate through all the parent mtd devices
- Grab a reference over them all but the master
- Only grab the master whith CONFIG_MTD_PARTITIONED_MASTER
Same logic must apply in the put path, otherwise it would be broken.

Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Alexander Usyskin <alexander.usyskin@intel.com>
Cc: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Fixes: 19bfa9eb ("mtd: use refcount to prevent corruption")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Alexander Usyskin <alexander.usyskin@intel.com>
Link: https://lore.kernel.org/linux-mtd/20230731090903.770277-1-miquel.raynal@bootlin.com

parent e9714c22

drivers/mtd/mtdcore.c

+10 −7

Original line number	Diff line number	Diff line
		@@ -1247,14 +1247,15 @@ int __get_mtd_device(struct mtd_info *mtd)
		return -ENODEV;
		}

		while (mtd) {
		if (mtd != master)
		kref_get(&mtd->refcnt);

		while (mtd->parent) {
		if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) \|\| mtd->parent != master)
		kref_get(&mtd->parent->refcnt);
		mtd = mtd->parent;
		}

		if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
		kref_get(&master->refcnt);

		return 0;
		}
		EXPORT_SYMBOL_GPL(__get_mtd_device);
		@@ -1338,9 +1339,11 @@ void __put_mtd_device(struct mtd_info *mtd)
		{
		struct mtd_info *master = mtd_get_master(mtd);

		while (mtd != master) {
		while (mtd) {
		/* kref_put() can relese mtd, so keep a reference mtd->parent */
		struct mtd_info *parent = mtd->parent;

		if (mtd != master)
		kref_put(&mtd->refcnt, mtd_device_release);
		mtd = parent;
		}