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Commit 9972cebb authored by Mike Christie's avatar Mike Christie Committed by Nicholas Bellinger
Browse files

tcmu: fix unmap thread race 



If the unmap thread has already run find_free_blocks
but not yet run prepare_to_wait when a wake_up(&unmap_wait)
call is done, the unmap thread is going to miss the wake
call. Instead of adding checks for if new waiters were added
this just has us use a work queue which will run us again
in this type of case.

Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 89ec9cfd

drivers/target/target_core_user.c

+10 −33
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ 
#include <linux/highmem.h>

#include <linux/configfs.h>

#include <linux/mutex.h>

#include <linux/kthread.h>

#include <linux/workqueue.h>

#include <net/genetlink.h>

#include <scsi/scsi_common.h>

#include <scsi/scsi_proto.h>
@@ -176,12 +176,11 @@ struct tcmu_cmd { 
	unsigned long flags;

};



static struct task_struct *unmap_thread;

static wait_queue_head_t unmap_wait;

static DEFINE_MUTEX(root_udev_mutex);

static LIST_HEAD(root_udev);



static atomic_t global_db_count = ATOMIC_INIT(0);

static struct work_struct tcmu_unmap_work;



static struct kmem_cache *tcmu_cmd_cache;
@@ -389,8 +388,7 @@ static bool tcmu_get_empty_blocks(struct tcmu_dev *udev, 


err:

	udev->waiting_global = true;

	/* Try to wake up the unmap thread */

	wake_up(&unmap_wait);

	schedule_work(&tcmu_unmap_work);

	return false;

}
@@ -1065,8 +1063,7 @@ static void tcmu_device_timedout(struct timer_list *t) 
	idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);

	spin_unlock_irqrestore(&udev->commands_lock, flags);



	/* Try to wake up the ummap thread */

	wake_up(&unmap_wait);

	schedule_work(&tcmu_unmap_work);



	/*

	 * We don't need to wakeup threads on wait_cmdr since they have their
@@ -2044,31 +2041,20 @@ static void run_cmdr_queues(void) 
	mutex_unlock(&root_udev_mutex);

}



static int unmap_thread_fn(void *data)

static void tcmu_unmap_work_fn(struct work_struct *work)

{

	while (!kthread_should_stop()) {

		DEFINE_WAIT(__wait);



		prepare_to_wait(&unmap_wait, &__wait, TASK_INTERRUPTIBLE);

		schedule();

		finish_wait(&unmap_wait, &__wait);



		if (kthread_should_stop())

			break;



	find_free_blocks();

	run_cmdr_queues();

}



	return 0;

}



static int __init tcmu_module_init(void)

{

	int ret, i, k, len = 0;



	BUILD_BUG_ON((sizeof(struct tcmu_cmd_entry) % TCMU_OP_ALIGN_SIZE) != 0);



	INIT_WORK(&tcmu_unmap_work, tcmu_unmap_work_fn);



	tcmu_cmd_cache = kmem_cache_create("tcmu_cmd_cache",

				sizeof(struct tcmu_cmd),

				__alignof__(struct tcmu_cmd),
@@ -2114,17 +2100,8 @@ static int __init tcmu_module_init(void) 
	if (ret)

		goto out_attrs;



	init_waitqueue_head(&unmap_wait);

	unmap_thread = kthread_run(unmap_thread_fn, NULL, "tcmu_unmap");

	if (IS_ERR(unmap_thread)) {

		ret = PTR_ERR(unmap_thread);

		goto out_unreg_transport;

	}



	return 0;



out_unreg_transport:

	target_backend_unregister(&tcmu_ops);

out_attrs:

	kfree(tcmu_attrs);

out_unreg_genl:
@@ -2139,7 +2116,7 @@ static int __init tcmu_module_init(void) 


static void __exit tcmu_module_exit(void)

{

	kthread_stop(unmap_thread);

	cancel_work_sync(&tcmu_unmap_work);

	target_backend_unregister(&tcmu_ops);

	kfree(tcmu_attrs);

	genl_unregister_family(&tcmu_genl_family);