On Wed, May 07, 2008 at 02:28:20PM +0100, Alasdair G Kergon wrote:
> On Wed, May 07, 2008 at 10:37:16AM +0200, Christof Schmitt wrote:
> > <4> [<000003e00008f79c>] multipath_dtr+0x38/0x50 [dm_multipath]
> > <4> [<000003e000077e4a>] dm_table_put+0xae/0x134 [dm_mod]
> > <4> [<000003e000076020>] dm_any_congested+0x50/0x88 [dm_mod]
>
> > I don't know, if this exact situation is reproducible, but we have a
> > memory dump that should have some more data.
>
> Well I'm guessing dm_any_congested() ran alongside a table reload, such
> that dm_any_congested() was still referencing the old table after
> dm_swap_table() removed it.
>
> IOW There needs to be better synchronisation between those two
> functions.
If the dm_swap_table should take care of the destruction, the attached
patch enforces this by letting the __unbind function wait until all
other users of the table did free their references to the table.
With this patch, the system survived a series of multipath failover
tests.
Signed-off-by: Christof Schmitt <christof.schmitt@xxxxxxxxxx>
---
drivers/md/dm-table.c | 7 +++++++
drivers/md/dm.c | 1 +
drivers/md/dm.h | 1 +
3 files changed, 9 insertions(+)
--- a/drivers/md/dm-table.c 2008-04-17 11:08:04.000000000 +0200
+++ b/drivers/md/dm-table.c 2008-06-16 17:00:36.000000000 +0200
@@ -27,6 +27,7 @@
struct dm_table {
struct mapped_device *md;
atomic_t holders;
+ wait_queue_head_t unbind_wait;
/* btree table */
unsigned int depth;
@@ -227,6 +228,7 @@ int dm_table_create(struct dm_table **re
INIT_LIST_HEAD(&t->devices);
atomic_set(&t->holders, 1);
+ init_waitqueue_head(&t->unbind_wait);
if (!num_targets)
num_targets = KEYS_PER_NODE;
@@ -1023,6 +1025,11 @@ struct mapped_device *dm_table_get_md(st
return t->md;
}
+void dm_table_wait(struct dm_table *map)
+{
+ wait_event(map->unbind_wait, atomic_read(&map->holders) == 1);
+}
+
EXPORT_SYMBOL(dm_vcalloc);
EXPORT_SYMBOL(dm_get_device);
EXPORT_SYMBOL(dm_put_device);
--- a/drivers/md/dm.c 2008-04-17 11:08:04.000000000 +0200
+++ b/drivers/md/dm.c 2008-06-16 16:57:24.000000000 +0200
@@ -1189,6 +1189,7 @@ static void __unbind(struct mapped_devic
write_lock(&md->map_lock);
md->map = NULL;
write_unlock(&md->map_lock);
+ dm_table_wait(map);
dm_table_put(map);
}
--- a/drivers/md/dm.h 2008-01-25 13:26:14.000000000 +0100
+++ b/drivers/md/dm.h 2008-06-16 16:56:32.000000000 +0200
@@ -111,6 +111,7 @@ void dm_table_postsuspend_targets(struct
int dm_table_resume_targets(struct dm_table *t);
int dm_table_any_congested(struct dm_table *t, int bdi_bits);
void dm_table_unplug_all(struct dm_table *t);
+void dm_table_wait(struct dm_table *map);
/*
* To check the return value from dm_table_find_target().
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
