On 1/18/19 10:32 PM, Martin Wilck wrote:
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@xxxxxxxx>
---
block/genhd.c | 22 ++++++++++++++++------
drivers/scsi/sd.c | 3 ++-
drivers/scsi/sr.c | 3 ++-
include/linux/genhd.h | 7 +++++++
4 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 1dd8fd6..bcd16f6 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1631,7 +1631,8 @@ static unsigned long disk_events_poll_jiffies(struct gendisk *disk)
*/
if (ev->poll_msecs >= 0)
intv_msecs = ev->poll_msecs;
- else if (disk->events & ~disk->async_events)
+ else if (disk->events & DISK_EVENT_FLAG_POLL
+ && disk->events & ~disk->async_events)
intv_msecs = disk_events_dfl_poll_msecs;
return msecs_to_jiffies(intv_msecs);
Hmm. That is an ... odd condition.
Clearly it's pointless to have the event bit set in the ->events mask if
it's already part of the ->async_events mask.
But shouldn't we better _prevent_ this from happening, ie refuse to set
DISK_EVENT_FLAG_POLL in events if it's already in ->async_events?
Then the above check would be simplified.
Cheers,
Hannes
