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Commit eea1bf38 authored by NeilBrown's avatar NeilBrown
Browse files

md: Fix is_mddev_idle test (again). 



There are two problems with is_mddev_idle.

1/ sync_io is 'atomic_t' and hence 'int'.  curr_events and all the
   rest are 'long'.
   So if sync_io were to wrap on a 64bit host, the value of
   curr_events would go very negative suddenly, and take a very
   long time to return to positive.

   So do all calculations as 'int'.  That gives us plenty of precision
   for what we need.

2/ To initialise rdev->last_events we simply call is_mddev_idle, on
   the assumption that it will make sure that last_events is in a
   suitable range.  It used to do this, but now it does not.
   So now we need to be more explicit about initialisation.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 99adcd9d

drivers/md/md.c

+8 −8
Original line number Diff line number Diff line
@@ -5716,18 +5716,18 @@ int unregister_md_personality(struct mdk_personality *p) 
	return 0;

}



static int is_mddev_idle(mddev_t *mddev)

static int is_mddev_idle(mddev_t *mddev, int init)

{

	mdk_rdev_t * rdev;

	int idle;

	long curr_events;

	int curr_events;



	idle = 1;

	rcu_read_lock();

	rdev_for_each_rcu(rdev, mddev) {

		struct gendisk *disk = rdev->bdev->bd_contains->bd_disk;

		curr_events = part_stat_read(&disk->part0, sectors[0]) +

				part_stat_read(&disk->part0, sectors[1]) -

		curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +

			      (int)part_stat_read(&disk->part0, sectors[1]) -

			      atomic_read(&disk->sync_io);

		/* sync IO will cause sync_io to increase before the disk_stats

		 * as sync_io is counted when a request starts, and
@@ -5751,7 +5751,7 @@ static int is_mddev_idle(mddev_t *mddev) 
		 * always make curr_events less than last_events.

		 *

		 */

		if (curr_events - rdev->last_events > 4096) {

		if (init || curr_events - rdev->last_events > 64) {

			rdev->last_events = curr_events;

			idle = 0;

		}
@@ -5994,7 +5994,7 @@ void md_do_sync(mddev_t *mddev) 
	       "(but not more than %d KB/sec) for %s.\n",

	       speed_max(mddev), desc);



	is_mddev_idle(mddev); /* this also initializes IO event counters */

	is_mddev_idle(mddev, 1); /* this initializes IO event counters */



	io_sectors = 0;

	for (m = 0; m < SYNC_MARKS; m++) {
@@ -6096,7 +6096,7 @@ void md_do_sync(mddev_t *mddev) 


		if (currspeed > speed_min(mddev)) {

			if ((currspeed > speed_max(mddev)) ||

					!is_mddev_idle(mddev)) {

					!is_mddev_idle(mddev, 0)) {

				msleep(500);

				goto repeat;

			}

include/linux/raid/md_k.h

+1 −1
Original line number Diff line number Diff line
@@ -51,7 +51,7 @@ struct mdk_rdev_s 


	sector_t size;			/* Device size (in blocks) */

	mddev_t *mddev;			/* RAID array if running */

	long last_events;		/* IO event timestamp */

	int last_events;		/* IO event timestamp */



	struct block_device *bdev;	/* block device handle */