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mtd: Clean refcounting with MTD_PARTITIONED_MASTER

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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: 19bfa9ebeb ("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
This commit is contained in:
Miquel Raynal 2023-07-31 11:09:03 +02:00
parent e9714c22c1
commit 264725e35f
1 changed files with 10 additions and 7 deletions
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17
drivers/mtd/mtdcore.c
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@ -1247,14 +1247,15 @@ int __get_mtd_device(struct mtd_info *mtd)
return -ENODEV;
}
kref_get(&mtd->refcnt);
while (mtd->parent) {
if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) || mtd->parent != master)
kref_get(&mtd->parent->refcnt);
while (mtd) {
if (mtd != master)
kref_get(&mtd->refcnt);
mtd = mtd->parent;
}
if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
kref_get(&master->refcnt);
return 0;
}
EXPORT_SYMBOL_GPL(__get_mtd_device);
@ -1338,10 +1339,12 @@ 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;
kref_put(&mtd->refcnt, mtd_device_release);
if (mtd != master)
kref_put(&mtd->refcnt, mtd_device_release);
mtd = parent;
}