linux-kernel - [PATCH/RFC] md: remove media-change code

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Message-id: <164991636542.11576.2282590308338864748@noble.neil.brown.name>
Date:   Thu, 14 Apr 2022 16:06:05 +1000
From:   "NeilBrown" <neilb@...e.de>
To:     Song Liu <song@...nel.org>, linux-raid@...r.kernel.org,
        linux-block@...r.kernel.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Lennart Poettering <lennart@...ttering.net>
Subject: [PATCH/RFC] md: remove media-change code


md only ever used the media-change interfaces to trigger a partition
rescan once the array became active.  Normally partition scan only
happens when the disk is first added, and with md the disk is typically
inactive when first added.

This rescan can now be achieved by simply setting GD_NEED_PART_SCAN.
So do that, and remove all the rescan.

This has the side effect of causing 'diskseq' to be stable for md devices.
Preciously diskseq would be incremented once the device became active
but no uevent would be generated to report this increment.  This was
confusing to systemd.

  https://github.com/systemd/systemd/pull/23011

Signed-off-by: NeilBrown <neilb@...e.de>
---
 drivers/md/md.c | 19 ++-----------------
 drivers/md/md.h |  2 --
 2 files changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 309b3af906ad..0ea4d34ec682 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5713,7 +5713,6 @@ static int md_alloc(dev_t dev, char *name)
 	mddev->queue = disk->queue;
 	blk_set_stacking_limits(&mddev->queue->limits);
 	blk_queue_write_cache(mddev->queue, true, true);
-	disk->events |= DISK_EVENT_MEDIA_CHANGE;
 	mddev->gendisk = disk;
 	error = add_disk(disk);
 	if (error)
@@ -6089,7 +6088,7 @@ int do_md_run(struct mddev *mddev)
 
 	set_capacity_and_notify(mddev->gendisk, mddev->array_sectors);
 	clear_bit(MD_NOT_READY, &mddev->flags);
-	mddev->changed = 1;
+	set_bit(GD_NEED_PART_SCAN, &mddev->gendisk->state);
 	kobject_uevent(&disk_to_dev(mddev->gendisk)->kobj, KOBJ_CHANGE);
 	sysfs_notify_dirent_safe(mddev->sysfs_state);
 	sysfs_notify_dirent_safe(mddev->sysfs_action);
@@ -6191,7 +6190,6 @@ static void md_clean(struct mddev *mddev)
 	mddev->sync_speed_min = mddev->sync_speed_max = 0;
 	mddev->recovery = 0;
 	mddev->in_sync = 0;
-	mddev->changed = 0;
 	mddev->degraded = 0;
 	mddev->safemode = 0;
 	mddev->private = NULL;
@@ -6407,7 +6405,7 @@ static int do_md_stop(struct mddev *mddev, int mode,
 
 		set_capacity_and_notify(disk, 0);
 		mutex_unlock(&mddev->open_mutex);
-		mddev->changed = 1;
+		set_bit(GD_NEED_PART_SCAN, &mddev->gendisk->state);
 
 		if (mddev->ro)
 			mddev->ro = 0;
@@ -7839,7 +7837,6 @@ static int md_open(struct block_device *bdev, fmode_t mode)
 	atomic_inc(&mddev->openers);
 	mutex_unlock(&mddev->open_mutex);
 
-	bdev_check_media_change(bdev);
  out:
 	if (err)
 		mddev_put(mddev);
@@ -7855,17 +7852,6 @@ static void md_release(struct gendisk *disk, fmode_t mode)
 	mddev_put(mddev);
 }
 
-static unsigned int md_check_events(struct gendisk *disk, unsigned int clearing)
-{
-	struct mddev *mddev = disk->private_data;
-	unsigned int ret = 0;
-
-	if (mddev->changed)
-		ret = DISK_EVENT_MEDIA_CHANGE;
-	mddev->changed = 0;
-	return ret;
-}
-
 const struct block_device_operations md_fops =
 {
 	.owner		= THIS_MODULE,
@@ -7877,7 +7863,6 @@ const struct block_device_operations md_fops =
 	.compat_ioctl	= md_compat_ioctl,
 #endif
 	.getgeo		= md_getgeo,
-	.check_events	= md_check_events,
 	.set_read_only	= md_set_read_only,
 };
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 6ac283864533..aec433ae5947 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -405,8 +405,6 @@ struct mddev {
 	atomic_t			active;		/* general refcount */
 	atomic_t			openers;	/* number of active opens */
 
-	int				changed;	/* True if we might need to
-							 * reread partition info */
 	int				degraded;	/* whether md should consider
 							 * adding a spare
 							 */
-- 
2.35.2