dm-delay: fix bugs introduced by kthread mode
This commit fixes the following bugs introduced by commit 70bbeb29fab0
("dm delay: for short delays, use kthread instead of timers and wq"):
* the function flush_worker_fn has no exit path - on unload, this
function will just loop and consume 100% CPU without any progress
* the wake-up mechanism in flush_worker_fn is racy - a wake up will be
missed if the process adds entries to the delayed_bios list just
before set_current_state(TASK_INTERRUPTIBLE)
* flush_delayed_bios_fast submits a bio while holding a global mutex;
this may deadlock if we have multiple stacked dm-delay devices and
the underlying device attempts to acquire the mutex too
* if the target constructor fails, it will call delay_dtr. delay_dtr
would attempt to free dc->timer_lock without it being initialized by
the constructor.
* if the target constructor's kthread allocation fails, delay_dtr
would crash trying to dereference dc->worker because it is non-NULL
due to ERR_PTR.
Fixes: 70bbeb29fab0 ("dm delay: for short delays, use kthread instead of timers and wq")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 2d6b900..00c09d9 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -73,39 +73,6 @@
return !!dc->worker;
}
-static void flush_delayed_bios_fast(struct delay_c *dc, bool flush_all)
-{
- struct dm_delay_info *delayed, *next;
-
- mutex_lock(&delayed_bios_lock);
- list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
- if (flush_all || time_after_eq(jiffies, delayed->expires)) {
- struct bio *bio = dm_bio_from_per_bio_data(delayed,
- sizeof(struct dm_delay_info));
- list_del(&delayed->list);
- dm_submit_bio_remap(bio, NULL);
- delayed->class->ops--;
- }
- }
- mutex_unlock(&delayed_bios_lock);
-}
-
-static int flush_worker_fn(void *data)
-{
- struct delay_c *dc = data;
-
- while (1) {
- flush_delayed_bios_fast(dc, false);
- if (unlikely(list_empty(&dc->delayed_bios))) {
- set_current_state(TASK_INTERRUPTIBLE);
- schedule();
- } else
- cond_resched();
- }
-
- return 0;
-}
-
static void flush_bios(struct bio *bio)
{
struct bio *n;
@@ -118,12 +85,11 @@
}
}
-static struct bio *flush_delayed_bios(struct delay_c *dc, bool flush_all)
+static void flush_delayed_bios_fast(struct delay_c *dc, bool flush_all)
{
struct dm_delay_info *delayed, *next;
- unsigned long next_expires = 0;
- unsigned long start_timer = 0;
- struct bio_list flush_bios = { };
+ struct bio_list flush_bio_list;
+ bio_list_init(&flush_bio_list);
mutex_lock(&delayed_bios_lock);
list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
@@ -131,7 +97,50 @@
struct bio *bio = dm_bio_from_per_bio_data(delayed,
sizeof(struct dm_delay_info));
list_del(&delayed->list);
- bio_list_add(&flush_bios, bio);
+ bio_list_add(&flush_bio_list, bio);
+ delayed->class->ops--;
+ }
+ }
+ mutex_unlock(&delayed_bios_lock);
+
+ flush_bios(bio_list_get(&flush_bio_list));
+}
+
+static int flush_worker_fn(void *data)
+{
+ struct delay_c *dc = data;
+
+ while (!kthread_should_stop()) {
+ flush_delayed_bios_fast(dc, false);
+ mutex_lock(&delayed_bios_lock);
+ if (unlikely(list_empty(&dc->delayed_bios))) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ mutex_unlock(&delayed_bios_lock);
+ schedule();
+ } else {
+ mutex_unlock(&delayed_bios_lock);
+ cond_resched();
+ }
+ }
+
+ return 0;
+}
+
+static void flush_delayed_bios(struct delay_c *dc, bool flush_all)
+{
+ struct dm_delay_info *delayed, *next;
+ unsigned long next_expires = 0;
+ unsigned long start_timer = 0;
+ struct bio_list flush_bio_list;
+ bio_list_init(&flush_bio_list);
+
+ mutex_lock(&delayed_bios_lock);
+ list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
+ if (flush_all || time_after_eq(jiffies, delayed->expires)) {
+ struct bio *bio = dm_bio_from_per_bio_data(delayed,
+ sizeof(struct dm_delay_info));
+ list_del(&delayed->list);
+ bio_list_add(&flush_bio_list, bio);
delayed->class->ops--;
continue;
}
@@ -147,7 +156,7 @@
if (start_timer)
queue_timeout(dc, next_expires);
- return bio_list_get(&flush_bios);
+ flush_bios(bio_list_get(&flush_bio_list));
}
static void flush_expired_bios(struct work_struct *work)
@@ -158,7 +167,7 @@
if (delay_is_fast(dc))
flush_delayed_bios_fast(dc, false);
else
- flush_bios(flush_delayed_bios(dc, false));
+ flush_delayed_bios(dc, false);
}
static void delay_dtr(struct dm_target *ti)
@@ -177,8 +186,7 @@
if (dc->worker)
kthread_stop(dc->worker);
- if (!delay_is_fast(dc))
- mutex_destroy(&dc->timer_lock);
+ mutex_destroy(&dc->timer_lock);
kfree(dc);
}
@@ -236,6 +244,7 @@
ti->private = dc;
INIT_LIST_HEAD(&dc->delayed_bios);
+ mutex_init(&dc->timer_lock);
dc->may_delay = true;
dc->argc = argc;
@@ -282,12 +291,12 @@
"dm-delay-flush-worker");
if (IS_ERR(dc->worker)) {
ret = PTR_ERR(dc->worker);
+ dc->worker = NULL;
goto bad;
}
} else {
timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
- mutex_init(&dc->timer_lock);
dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
if (!dc->kdelayd_wq) {
ret = -EINVAL;
@@ -345,11 +354,11 @@
dc->may_delay = false;
mutex_unlock(&delayed_bios_lock);
- if (delay_is_fast(dc))
+ if (delay_is_fast(dc)) {
flush_delayed_bios_fast(dc, true);
- else {
+ } else {
del_timer_sync(&dc->delay_timer);
- flush_bios(flush_delayed_bios(dc, true));
+ flush_delayed_bios(dc, true);
}
}
