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 091429d2c7c9b01c42f986c04198bde9775f4014..f6ecddb79952b9a132fd0380b8732102db0c641e 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1487,9 +1487,9 @@ 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)
-               queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+               queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);
        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);
 }
@@ -1530,7 +1530,7 @@ void disk_check_events(struct gendisk *disk)
        spin_lock_irqsave(&ev->lock, flags);
        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_irqrestore(&ev->lock, flags);
 }
@@ -1568,7 +1568,7 @@ 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);
-       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);
 
@@ -1605,7 +1605,7 @@ static void disk_events_workfn(struct work_struct *work)
 
        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);
 

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index f584aba78ca9a8d1add3b73797811b5a34071357..6c56a14a70d973002cc0b0449611014d9962936d 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_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_nrt_freezable_wq;
 
 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 aec02b6a1c4a4b70ae0eb1c15fc40b93b726c849..1456daba9a08b426e8485a4ef687616b5ee01951 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -252,11 +252,13 @@ 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_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_nrt_freezable_wq);
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/workqueue.h>
@@ -3796,8 +3798,11 @@ static int __init init_workqueues(void)
                                            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 ||
-              !system_unbound_wq || !system_freezable_wq);
+              !system_unbound_wq || !system_freezable_wq ||
+               !system_nrt_freezable_wq);
        return 0;
 }
 early_initcall(init_workqueues);