Commit 635f6416 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid10: locking changes for 'enough()'. 



As 'enough' accesses conf->prev and conf->geo, which can change
spontanously, it should guard against changes.
This can be done with device_lock as start_reshape holds device_lock
while updating 'geo' and end_reshape holds it while updating 'prev'.

So 'error' needs to hold 'device_lock'.

On the other hand, raid10_end_read_request knows which of the two it
really wants to access, and as it is an active request on that one,
the value cannot change underneath it.

So change _enough to take flag rather than a pointer, pass the
appropriate flag from raid10_end_read_request(), and remove the locking.

All other calls to 'enough' are made with reconfig_mutex held, so
neither 'prev' nor 'geo' can change.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent b29bebd6

drivers/md/raid10.c

+29 −16
Original line number Diff line number Diff line
@@ -97,7 +97,7 @@ static int max_queued_requests = 1024; 


static void allow_barrier(struct r10conf *conf);

static void lower_barrier(struct r10conf *conf);

static int enough(struct r10conf *conf, int ignore);

static int _enough(struct r10conf *conf, int previous, int ignore);

static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,

				int *skipped);

static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio);
@@ -392,11 +392,9 @@ static void raid10_end_read_request(struct bio *bio, int error) 
		 * than fail the last device.  Here we redefine

		 * "uptodate" to mean "Don't want to retry"

		 */

		unsigned long flags;

		spin_lock_irqsave(&conf->device_lock, flags);

		if (!enough(conf, rdev->raid_disk))

		if (!_enough(conf, test_bit(R10BIO_Previous, &r10_bio->state),

			     rdev->raid_disk))

			uptodate = 1;

		spin_unlock_irqrestore(&conf->device_lock, flags);

	}

	if (uptodate) {

		raid_end_bio_io(r10_bio);
@@ -1632,9 +1630,17 @@ static void status(struct seq_file *seq, struct mddev *mddev) 
 * Don't consider the device numbered 'ignore'

 * as we might be about to remove it.

 */

static int _enough(struct r10conf *conf, struct geom *geo, int ignore)

static int _enough(struct r10conf *conf, int previous, int ignore)

{

	int first = 0;

	int disks, ncopies;

	if (previous) {

		disks = conf->prev.raid_disks;

		ncopies = conf->prev.near_copies;

	} else {

		disks = conf->geo.raid_disks;

		ncopies = conf->geo.near_copies;

	}



	do {

		int n = conf->copies;
@@ -1644,25 +1650,31 @@ static int _enough(struct r10conf *conf, struct geom *geo, int ignore) 
			if (conf->mirrors[this].rdev &&

			    this != ignore)

				cnt++;

			this = (this+1) % geo->raid_disks;

			this = (this+1) % disks;

		}

		if (cnt == 0)

			return 0;

		first = (first + geo->near_copies) % geo->raid_disks;

		first = (first + ncopies) % disks;

	} while (first != 0);

	return 1;

}



static int enough(struct r10conf *conf, int ignore)

{

	return _enough(conf, &conf->geo, ignore) &&

		_enough(conf, &conf->prev, ignore);

	/* when calling 'enough', both 'prev' and 'geo' must

	 * be stable.

	 * This is ensured if ->reconfig_mutex or ->device_lock

	 * is held.

	 */

	return _enough(conf, 0, ignore) &&

		_enough(conf, 1, ignore);

}



static void error(struct mddev *mddev, struct md_rdev *rdev)

{

	char b[BDEVNAME_SIZE];

	struct r10conf *conf = mddev->private;

	unsigned long flags;



	/*

	 * If it is not operational, then we have already marked it as dead
@@ -1670,17 +1682,17 @@ static void error(struct mddev *mddev, struct md_rdev *rdev) 
	 * next level up know.

	 * else mark the drive as failed

	 */

	spin_lock_irqsave(&conf->device_lock, flags);

	if (test_bit(In_sync, &rdev->flags)

	    && !enough(conf, rdev->raid_disk))

	    && !enough(conf, rdev->raid_disk)) {

		/*

		 * Don't fail the drive, just return an IO error.

		 */

		spin_unlock_irqrestore(&conf->device_lock, flags);

		return;

	}

	if (test_and_clear_bit(In_sync, &rdev->flags)) {

		unsigned long flags;

		spin_lock_irqsave(&conf->device_lock, flags);

		mddev->degraded++;

		spin_unlock_irqrestore(&conf->device_lock, flags);

			/*

		 * if recovery is running, make sure it aborts.

		 */
@@ -1689,6 +1701,7 @@ static void error(struct mddev *mddev, struct md_rdev *rdev) 
	set_bit(Blocked, &rdev->flags);

	set_bit(Faulty, &rdev->flags);

	set_bit(MD_CHANGE_DEVS, &mddev->flags);

	spin_unlock_irqrestore(&conf->device_lock, flags);

	printk(KERN_ALERT

	       "md/raid10:%s: Disk failure on %s, disabling device.\n"

	       "md/raid10:%s: Operation continuing on %d devices.\n",
@@ -1791,7 +1804,7 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev) 
		 * very different from resync

		 */

		return -EBUSY;

	if (rdev->saved_raid_disk < 0 && !_enough(conf, &conf->prev, -1))

	if (rdev->saved_raid_disk < 0 && !_enough(conf, 1, -1))

		return -EINVAL;



	if (rdev->raid_disk >= 0)

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