[PATCH RESEND v2 2/5] block: disk_events: introduce event flags

[Martin Wilck <mwilck@suse.com>]

Currently, an empty disk->events field tells the block layer not to forward
media change events to user space. This was done in
commit 7c88a168da80 ("block: don't propagate unlisted DISK_EVENTs to userland")
in order to avoid events from "fringe" drivers to be forwarded to user
space. By doing so, the block layer lost the information which events were
supported by a particular block device, and most importantly, whether or
not a given device supports media change events at all.

Prepare for not interpreting the "events" field this way in the future any
more. This is done by adding two flag bits that can be set to have the
device treated like one that has the "events" field set to a non-zero value
before. This applies only to the sd and sr drivers, which are changed to
set the new flags.

The new flags are DISK_EVENT_FLAG_POLL to enforce polling of the device for
synchronous events, and DISK_EVENT_FLAG_UEVENT to tell the blocklayer to
generate udev events from kernel events. They can easily be fit in the int
reserved for event bits.

This patch doesn't change behavior.

Signed-off-by: Martin Wilck <mwilck@suse.com>
---
 block/genhd.c         | 15 ++++++++++-----
 drivers/scsi/sd.c     |  3 ++-
 drivers/scsi/sr.c     |  3 ++-
 include/linux/genhd.h |  7 +++++++
 4 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index ee76de0..cc6c52d1 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1632,7 +1632,7 @@ static unsigned long disk_events_poll_jiffies(struct gendisk *disk)
 	 */
 	if (ev->poll_msecs >= 0)
 		intv_msecs = ev->poll_msecs;
-	else if (disk->events)
+	else if (disk->events & DISK_EVENT_FLAG_POLL)
 		intv_msecs = disk_events_dfl_poll_msecs;
 
 	return msecs_to_jiffies(intv_msecs);
@@ -1842,11 +1842,13 @@ static void disk_check_events(struct disk_events *ev,
 
 	/*
 	 * Tell userland about new events.  Only the events listed in
-	 * @disk->events are reported.  Unlisted events are processed the
-	 * same internally but never get reported to userland.
+	 * @disk->events are reported, and only if DISK_EVENT_FLAG_UEVENT
+	 * is set. Otherwise, events are processed internally but never
+	 * get reported to userland.
 	 */
 	for (i = 0; i < ARRAY_SIZE(disk_uevents); i++)
-		if (events & disk->events & (1 << i))
+		if (events & disk->events & (1 << i) &&
+		    disk->events & DISK_EVENT_FLAG_UEVENT)
 			envp[nr_events++] = disk_uevents[i];
 
 	if (nr_events)
@@ -1884,7 +1886,10 @@ static ssize_t disk_events_show(struct device *dev,
 {
 	struct gendisk *disk = dev_to_disk(dev);
 
-	return __disk_events_show(disk->events, buf);
+	if (!(disk->events & DISK_EVENT_FLAG_UEVENT))
+		return 0;
+
+	return __disk_events_show(disk->events & DISK_EVENT_TYPES_MASK, buf);
 }
 
 static ssize_t disk_events_async_show(struct device *dev,
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 251db30..71a8a1b 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3326,7 +3326,8 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
 	gd->flags = GENHD_FL_EXT_DEVT;
 	if (sdp->removable) {
 		gd->flags |= GENHD_FL_REMOVABLE;
-		gd->events |= DISK_EVENT_MEDIA_CHANGE;
+		gd->events |= DISK_EVENT_MEDIA_CHANGE |
+			DISK_EVENT_FLAG_POLL | DISK_EVENT_FLAG_UEVENT;
 	}
 
 	blk_pm_runtime_init(sdp->request_queue, dev);
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 039c27c2..f7a9d34 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -715,7 +715,8 @@ static int sr_probe(struct device *dev)
 	sprintf(disk->disk_name, "sr%d", minor);
 	disk->fops = &sr_bdops;
 	disk->flags = GENHD_FL_CD | GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE;
-	disk->events = DISK_EVENT_MEDIA_CHANGE | DISK_EVENT_EJECT_REQUEST;
+	disk->events = DISK_EVENT_MEDIA_CHANGE | DISK_EVENT_EJECT_REQUEST
+		| DISK_EVENT_FLAG_POLL | DISK_EVENT_FLAG_UEVENT;
 
 	blk_queue_rq_timeout(sdev->request_queue, SR_TIMEOUT);
 
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 5f78edb..a3d5b1c 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -148,8 +148,15 @@ struct hd_struct {
 enum {
 	DISK_EVENT_MEDIA_CHANGE			= 1 << 0, /* media changed */
 	DISK_EVENT_EJECT_REQUEST		= 1 << 1, /* eject requested */
+	/* Poll even if events_poll_msecs is unset */
+	DISK_EVENT_FLAG_POLL			= 1 << 16,
+	/* Forward events to udev */
+	DISK_EVENT_FLAG_UEVENT			= 1 << 17,
 };
 
+#define DISK_EVENT_TYPES_MASK \
+	(DISK_EVENT_MEDIA_CHANGE | DISK_EVENT_EJECT_REQUEST)
+
 struct disk_part_tbl {
 	struct rcu_head rcu_head;
 	int len;
-- 
2.21.0