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block: check_events: don't bother with events if unsupported 

Drivers now report to the block layer if they support media change
events. If this is not the case, there's no need to allocate the event
structure, and all event handling code can effectively be skipped. This
simplifies code flow in particular for non-removable sd devices.

This effectively reverts commit 75e3f3ee3c ("block: always allocate
genhd->ev if check_events is implemented").

The sysfs files for the events are kept in place even if no events are
supported, as user space may rely on them being present. The only
difference is that an error code is now returned if the user tries to
set poll_msecs.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Martin Wilck 2019-03-27 14:51:05 +01:00 committed by Jens Axboe
parent 773008f6fe
commit cdf3e3deb7
1 changed files with 16 additions and 11 deletions
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27
block/genhd.c
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@ -1904,6 +1904,9 @@ static ssize_t disk_events_poll_msecs_show(struct device *dev,
{
struct gendisk *disk = dev_to_disk(dev);
if (!disk->ev)
return sprintf(buf, "-1\n");
return sprintf(buf, "%ld\n", disk->ev->poll_msecs);
}
@ -1920,6 +1923,9 @@ static ssize_t disk_events_poll_msecs_store(struct device *dev,
if (intv < 0 && intv != -1)
return -EINVAL;
if (!disk->ev)
return -ENODEV;
disk_block_events(disk);
disk->ev->poll_msecs = intv;
__disk_unblock_events(disk, true);
@ -1984,7 +1990,7 @@ static void disk_alloc_events(struct gendisk *disk)
{
struct disk_events *ev;
if (!disk->fops->check_events)
if (!disk->fops->check_events || !disk->events)
return;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
@ -2006,14 +2012,14 @@ static void disk_alloc_events(struct gendisk *disk)
static void disk_add_events(struct gendisk *disk)
{
if (!disk->ev)
return;
/* FIXME: error handling */
if (sysfs_create_files(&disk_to_dev(disk)->kobj, disk_events_attrs) < 0)
pr_warn("%s: failed to create sysfs files for events\n",
disk->disk_name);
if (!disk->ev)
return;
mutex_lock(&disk_events_mutex);
list_add_tail(&disk->ev->node, &disk_events);
mutex_unlock(&disk_events_mutex);
@ -2027,14 +2033,13 @@ static void disk_add_events(struct gendisk *disk)
static void disk_del_events(struct gendisk *disk)
{
if (!disk->ev)
return;
if (disk->ev) {
disk_block_events(disk);
disk_block_events(disk);
mutex_lock(&disk_events_mutex);
list_del_init(&disk->ev->node);
mutex_unlock(&disk_events_mutex);
mutex_lock(&disk_events_mutex);
list_del_init(&disk->ev->node);
mutex_unlock(&disk_events_mutex);
}
sysfs_remove_files(&disk_to_dev(disk)->kobj, disk_events_attrs);
}