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dm: bind new table before destroying old

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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: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Alasdair G Kergon 2009-12-10 23:52:23 +00:00
parent 1d0f3ce832
commit a794015597
2 changed files with 14 additions and 5 deletions
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3
drivers/md/dm-table.c
View file

@ -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();

16
drivers/md/dm.c
View file

@ -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);