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Commit a7940155 authored by Alasdair G Kergon's avatar Alasdair G Kergon
Browse files

dm: bind new table before destroying old 



When replacing a mapped device's table during a 'resume', delay the
destruction of the old table until the new one is successfully in place.

This will make it easier for a later patch to transfer internal state
information from the old table to the new one (something we do not currently
support) while giving us more options for reversion if a later part
of the operation fails.

Devices are always in the suspended state during dm_swap_table().
This patch reinforces the requirement that all I/O must have been
flushed from the table targets while in this state (including any in
workqueues).  In the case of 'noflush' suspending, unprocessed
I/O should have been 'pushed back' to the dm core prior to this point,
for resubmission after the new table is in place.

Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 1d0f3ce8

drivers/md/dm-table.c

+3 −0
Original line number Diff line number Diff line
@@ -237,6 +237,9 @@ void dm_table_destroy(struct dm_table *t) 
{

	unsigned int i;



	if (!t)

		return;



	while (atomic_read(&t->holders))

		msleep(1);

	smp_mb();

drivers/md/dm.c

+11 −5
Original line number Diff line number Diff line
@@ -2077,19 +2077,23 @@ static int __bind(struct mapped_device *md, struct dm_table *t, 
	return 0;

}



static void __unbind(struct mapped_device *md)

/*

 * Returns unbound table for the caller to free.

 */

static struct dm_table *__unbind(struct mapped_device *md)

{

	struct dm_table *map = md->map;

	unsigned long flags;



	if (!map)

		return;

		return NULL;



	dm_table_event_callback(map, NULL, NULL);

	write_lock_irqsave(&md->map_lock, flags);

	md->map = NULL;

	write_unlock_irqrestore(&md->map_lock, flags);

	dm_table_destroy(map);



	return map;

}



/*
@@ -2182,7 +2186,7 @@ void dm_put(struct mapped_device *md) 
		}

		dm_sysfs_exit(md);

		dm_table_put(map);

		__unbind(md);

		dm_table_destroy(__unbind(md));

		free_dev(md);

	}

}
@@ -2368,6 +2372,7 @@ static void dm_rq_barrier_work(struct work_struct *work) 
 */

int dm_swap_table(struct mapped_device *md, struct dm_table *table)

{

	struct dm_table *map;

	struct queue_limits limits;

	int r = -EINVAL;
@@ -2388,8 +2393,9 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table) 
		goto out;

	}



	__unbind(md);

	map = __unbind(md);

	r = __bind(md, table, &limits);

	dm_table_destroy(map);



out:

	mutex_unlock(&md->suspend_lock);