Block: use a freezable workqueue for disk-event polling

commit 62d3c5439c534b0e6c653fc63e6d8c67be3a57b1 upstream.

This patch (as1519) fixes a bug in the block layer's disk-events
polling.  The polling is done by a work routine queued on the
system_nrt_wq workqueue.  Since that workqueue isn't freezable, the
polling continues even in the middle of a system sleep transition.

Obviously, polling a suspended drive for media changes and such isn't
a good thing to do; in the case of USB mass-storage devices it can
lead to real problems requiring device resets and even re-enumeration.

The patch fixes things by creating a new system-wide, non-reentrant,
freezable workqueue and using it for disk-events polling.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/block/genhd.c b/block/genhd.c
index 9db720d..997afd6 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1479,9 +1479,9 @@ static void __disk_unblock_events(struct gendisk *disk, bool check_now)
        intv = disk_events_poll_jiffies(disk);
        set_timer_slack(&ev->dwork.timer, intv / 4);
        if (check_now)
        intv = disk_events_poll_jiffies(disk);
        set_timer_slack(&ev->dwork.timer, intv / 4);
        if (check_now)

-               queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+               queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);

        else if (intv)
        else if (intv)

-               queue_delayed_work(system_nrt_wq, &ev->dwork, intv);
+               queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, intv);

 out_unlock:
        spin_unlock_irqrestore(&ev->lock, flags);
 }
 out_unlock:
        spin_unlock_irqrestore(&ev->lock, flags);
 }


@@ -1525,7 +1525,7 @@ void disk_flush_events(struct gendisk *disk, unsigned int mask)
        ev->clearing |= mask;
        if (!ev->block) {
                cancel_delayed_work(&ev->dwork);
        ev->clearing |= mask;
        if (!ev->block) {
                cancel_delayed_work(&ev->dwork);

-               queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+               queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);

        }
        spin_unlock_irq(&ev->lock);
 }
        }
        spin_unlock_irq(&ev->lock);
 }


@@ -1562,7 +1562,7 @@ unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask)
 
        /* uncondtionally schedule event check and wait for it to finish */
        disk_block_events(disk);
 
        /* uncondtionally schedule event check and wait for it to finish */
        disk_block_events(disk);

-       queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+       queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);

        flush_delayed_work(&ev->dwork);
        __disk_unblock_events(disk, false);
 
        flush_delayed_work(&ev->dwork);
        __disk_unblock_events(disk, false);
 


@@ -1599,7 +1599,7 @@ static void disk_events_workfn(struct work_struct *work)
 
        intv = disk_events_poll_jiffies(disk);
        if (!ev->block && intv)
 
        intv = disk_events_poll_jiffies(disk);
        if (!ev->block && intv)

-               queue_delayed_work(system_nrt_wq, &ev->dwork, intv);
+               queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, intv);

 
        spin_unlock_irq(&ev->lock);
 
 
        spin_unlock_irq(&ev->lock);
 

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 0d556de..e228ca9 100644 (file)
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -289,12 +289,16 @@ enum {
  *
  * system_freezable_wq is equivalent to system_wq except that it's
  * freezable.
  *
  * system_freezable_wq is equivalent to system_wq except that it's
  * freezable.

+ *
+ * system_nrt_freezable_wq is equivalent to system_nrt_wq except that
+ * it's freezable.

  */
 extern struct workqueue_struct *system_wq;
 extern struct workqueue_struct *system_long_wq;
 extern struct workqueue_struct *system_nrt_wq;
 extern struct workqueue_struct *system_unbound_wq;
 extern struct workqueue_struct *system_freezable_wq;
  */
 extern struct workqueue_struct *system_wq;
 extern struct workqueue_struct *system_long_wq;
 extern struct workqueue_struct *system_nrt_wq;
 extern struct workqueue_struct *system_unbound_wq;
 extern struct workqueue_struct *system_freezable_wq;

+extern struct workqueue_struct *system_nrt_freezable_wq;

 
 extern struct workqueue_struct *
 __alloc_workqueue_key(const char *name, unsigned int flags, int max_active,
 
 extern struct workqueue_struct *
 __alloc_workqueue_key(const char *name, unsigned int flags, int max_active,

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 42fa9ad..bb425b1 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -253,11 +253,13 @@ struct workqueue_struct *system_long_wq __read_mostly;
 struct workqueue_struct *system_nrt_wq __read_mostly;
 struct workqueue_struct *system_unbound_wq __read_mostly;
 struct workqueue_struct *system_freezable_wq __read_mostly;
 struct workqueue_struct *system_nrt_wq __read_mostly;
 struct workqueue_struct *system_unbound_wq __read_mostly;
 struct workqueue_struct *system_freezable_wq __read_mostly;

+struct workqueue_struct *system_nrt_freezable_wq __read_mostly;

 EXPORT_SYMBOL_GPL(system_wq);
 EXPORT_SYMBOL_GPL(system_long_wq);
 EXPORT_SYMBOL_GPL(system_nrt_wq);
 EXPORT_SYMBOL_GPL(system_unbound_wq);
 EXPORT_SYMBOL_GPL(system_freezable_wq);
 EXPORT_SYMBOL_GPL(system_wq);
 EXPORT_SYMBOL_GPL(system_long_wq);
 EXPORT_SYMBOL_GPL(system_nrt_wq);
 EXPORT_SYMBOL_GPL(system_unbound_wq);
 EXPORT_SYMBOL_GPL(system_freezable_wq);

+EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);

 
 #define CREATE_TRACE_POINTS
 #include <trace/events/workqueue.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/workqueue.h>


@@ -3821,8 +3823,11 @@ static int __init init_workqueues(void)
                                            WQ_UNBOUND_MAX_ACTIVE);
        system_freezable_wq = alloc_workqueue("events_freezable",
                                              WQ_FREEZABLE, 0);
                                            WQ_UNBOUND_MAX_ACTIVE);
        system_freezable_wq = alloc_workqueue("events_freezable",
                                              WQ_FREEZABLE, 0);

+       system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable",
+                       WQ_NON_REENTRANT | WQ_FREEZABLE, 0);

        BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
        BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||

-              !system_unbound_wq || !system_freezable_wq);
+              !system_unbound_wq || !system_freezable_wq ||
+               !system_nrt_freezable_wq);

        return 0;
 }
 early_initcall(init_workqueues);
        return 0;
 }
 early_initcall(init_workqueues);