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path: root/drivers/block/loop.c
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Diffstat (limited to 'drivers/block/loop.c')
-rw-r--r--drivers/block/loop.c75
1 files changed, 49 insertions, 26 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index fa1c298a8cfb..7bf4686af774 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2111,18 +2111,6 @@ int loop_register_transfer(struct loop_func_table *funcs)
return 0;
}
-static int unregister_transfer_cb(int id, void *ptr, void *data)
-{
- struct loop_device *lo = ptr;
- struct loop_func_table *xfer = data;
-
- mutex_lock(&lo->lo_mutex);
- if (lo->lo_encryption == xfer)
- loop_release_xfer(lo);
- mutex_unlock(&lo->lo_mutex);
- return 0;
-}
-
int loop_unregister_transfer(int number)
{
unsigned int n = number;
@@ -2130,9 +2118,20 @@ int loop_unregister_transfer(int number)
if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
return -EINVAL;
+ /*
+ * This function is called from only cleanup_cryptoloop().
+ * Given that each loop device that has a transfer enabled holds a
+ * reference to the module implementing it we should never get here
+ * with a transfer that is set (unless forced module unloading is
+ * requested). Thus, check module's refcount and warn if this is
+ * not a clean unloading.
+ */
+#ifdef CONFIG_MODULE_UNLOAD
+ if (xfer->owner && module_refcount(xfer->owner) != -1)
+ pr_err("Danger! Unregistering an in use transfer function.\n");
+#endif
xfer_funcs[n] = NULL;
- idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
return 0;
}
@@ -2323,8 +2322,9 @@ static int loop_add(int i)
} else {
err = idr_alloc(&loop_index_idr, lo, 0, 0, GFP_KERNEL);
}
+ mutex_unlock(&loop_ctl_mutex);
if (err < 0)
- goto out_unlock;
+ goto out_free_dev;
i = err;
err = -ENOMEM;
@@ -2393,15 +2393,19 @@ static int loop_add(int i)
disk->events = DISK_EVENT_MEDIA_CHANGE;
disk->event_flags = DISK_EVENT_FLAG_UEVENT;
sprintf(disk->disk_name, "loop%d", i);
+ /* Make this loop device reachable from pathname. */
add_disk(disk);
+ /* Show this loop device. */
+ mutex_lock(&loop_ctl_mutex);
+ lo->idr_visible = true;
mutex_unlock(&loop_ctl_mutex);
return i;
out_cleanup_tags:
blk_mq_free_tag_set(&lo->tag_set);
out_free_idr:
+ mutex_lock(&loop_ctl_mutex);
idr_remove(&loop_index_idr, i);
-out_unlock:
mutex_unlock(&loop_ctl_mutex);
out_free_dev:
kfree(lo);
@@ -2411,9 +2415,14 @@ out:
static void loop_remove(struct loop_device *lo)
{
+ /* Make this loop device unreachable from pathname. */
del_gendisk(lo->lo_disk);
blk_cleanup_disk(lo->lo_disk);
blk_mq_free_tag_set(&lo->tag_set);
+ mutex_lock(&loop_ctl_mutex);
+ idr_remove(&loop_index_idr, lo->lo_number);
+ mutex_unlock(&loop_ctl_mutex);
+ /* There is no route which can find this loop device. */
mutex_destroy(&lo->lo_mutex);
kfree(lo);
}
@@ -2437,31 +2446,40 @@ static int loop_control_remove(int idx)
return -EINVAL;
}
+ /* Hide this loop device for serialization. */
ret = mutex_lock_killable(&loop_ctl_mutex);
if (ret)
return ret;
-
lo = idr_find(&loop_index_idr, idx);
- if (!lo) {
+ if (!lo || !lo->idr_visible)
ret = -ENODEV;
- goto out_unlock_ctrl;
- }
+ else
+ lo->idr_visible = false;
+ mutex_unlock(&loop_ctl_mutex);
+ if (ret)
+ return ret;
+ /* Check whether this loop device can be removed. */
ret = mutex_lock_killable(&lo->lo_mutex);
if (ret)
- goto out_unlock_ctrl;
+ goto mark_visible;
if (lo->lo_state != Lo_unbound ||
atomic_read(&lo->lo_refcnt) > 0) {
mutex_unlock(&lo->lo_mutex);
ret = -EBUSY;
- goto out_unlock_ctrl;
+ goto mark_visible;
}
+ /* Mark this loop device no longer open()-able. */
lo->lo_state = Lo_deleting;
mutex_unlock(&lo->lo_mutex);
- idr_remove(&loop_index_idr, lo->lo_number);
loop_remove(lo);
-out_unlock_ctrl:
+ return 0;
+
+mark_visible:
+ /* Show this loop device again. */
+ mutex_lock(&loop_ctl_mutex);
+ lo->idr_visible = true;
mutex_unlock(&loop_ctl_mutex);
return ret;
}
@@ -2475,7 +2493,8 @@ static int loop_control_get_free(int idx)
if (ret)
return ret;
idr_for_each_entry(&loop_index_idr, lo, id) {
- if (lo->lo_state == Lo_unbound)
+ /* Hitting a race results in creating a new loop device which is harmless. */
+ if (lo->idr_visible && data_race(lo->lo_state) == Lo_unbound)
goto found;
}
mutex_unlock(&loop_ctl_mutex);
@@ -2591,10 +2610,14 @@ static void __exit loop_exit(void)
unregister_blkdev(LOOP_MAJOR, "loop");
misc_deregister(&loop_misc);
- mutex_lock(&loop_ctl_mutex);
+ /*
+ * There is no need to use loop_ctl_mutex here, for nobody else can
+ * access loop_index_idr when this module is unloading (unless forced
+ * module unloading is requested). If this is not a clean unloading,
+ * we have no means to avoid kernel crash.
+ */
idr_for_each_entry(&loop_index_idr, lo, id)
loop_remove(lo);
- mutex_unlock(&loop_ctl_mutex);
idr_destroy(&loop_index_idr);
}