From 25705e3a3e9f91280b51124a28e74418aff00c7d Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Fri, 2 Mar 2012 10:51:00 +0100
Subject: 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>
---
 block/genhd.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

(limited to 'block/genhd.c')

diff --git a/block/genhd.c b/block/genhd.c
index 091429d..f6ecddb 100644
--- 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);
 
-- 
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