dm: avoid _hash_lock deadlock

[firefly-linux-kernel-4.4.55.git] / drivers / md / dm-ioctl.c

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index a679429315828eef8e4cbe896b8cdfba00f5eda2..d19854c98184de70a6ba7bb5432543eecd212a04 100644 (file)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -56,6 +56,11 @@ static void dm_hash_remove_all(int keep_open_devices);
  */
 static DECLARE_RWSEM(_hash_lock);
 
+/*
+ * Protects use of mdptr to obtain hash cell name and uuid from mapped device.
+ */
+static DEFINE_MUTEX(dm_hash_cells_mutex);
+
 static void init_buckets(struct list_head *buckets)
 {
        unsigned int i;
@@ -206,7 +211,9 @@ static int dm_hash_insert(const char *name, const char *uuid, struct mapped_devi
                list_add(&cell->uuid_list, _uuid_buckets + hash_str(uuid));
        }
        dm_get(md);
+       mutex_lock(&dm_hash_cells_mutex);
        dm_set_mdptr(md, cell);
+       mutex_unlock(&dm_hash_cells_mutex);
        up_write(&_hash_lock);
 
        return 0;
@@ -224,7 +231,9 @@ static void __hash_remove(struct hash_cell *hc)
        /* remove from the dev hash */
        list_del(&hc->uuid_list);
        list_del(&hc->name_list);
+       mutex_lock(&dm_hash_cells_mutex);
        dm_set_mdptr(hc->md, NULL);
+       mutex_unlock(&dm_hash_cells_mutex);
 
        table = dm_get_table(hc->md);
        if (table) {
@@ -321,7 +330,9 @@ static int dm_hash_rename(uint32_t cookie, const char *old, const char *new)
         */
        list_del(&hc->name_list);
        old_name = hc->name;
+       mutex_lock(&dm_hash_cells_mutex);
        hc->name = new_name;
+       mutex_unlock(&dm_hash_cells_mutex);
        list_add(&hc->name_list, _name_buckets + hash_str(new_name));
 
        /*
@@ -1582,8 +1593,7 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
        if (!md)
                return -ENXIO;
 
-       dm_get(md);
-       down_read(&_hash_lock);
+       mutex_lock(&dm_hash_cells_mutex);
        hc = dm_get_mdptr(md);
        if (!hc || hc->md != md) {
                r = -ENXIO;
@@ -1596,8 +1606,7 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
                strcpy(uuid, hc->uuid ? : "");
 
 out:
-       up_read(&_hash_lock);
-       dm_put(md);
+       mutex_unlock(&dm_hash_cells_mutex);
 
        return r;
 }