Questions:
Do all the targets correctly flush or push back everything during a
suspend (including workqueues)?
Do all the targets correctly sync to disk all internal state that
needs to be preserved during a suspend?
In other words, in the case of an already-suspended target, the target
'dtr' functions should only be freeing memory and other resources and
not causing I/O to any of the table's devices.
All targets are supposed to be behave this way already, but please
would you check the targets with which you are familiar anyway?
Alasdair
From: Alasdair G Kergon <agk@xxxxxxxxxx>
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@xxxxxxxxxx>
---
drivers/md/dm-table.c | 3 +++
drivers/md/dm.c | 13 +++++++++----
2 files changed, 12 insertions(+), 4 deletions(-)
Index: linux-2.6.32-rc6/drivers/md/dm-table.c
===================================================================
--- linux-2.6.32-rc6.orig/drivers/md/dm-table.c
+++ linux-2.6.32-rc6/drivers/md/dm-table.c
@@ -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();
Index: linux-2.6.32-rc6/drivers/md/dm.c
===================================================================
--- linux-2.6.32-rc6.orig/drivers/md/dm.c
+++ linux-2.6.32-rc6/drivers/md/dm.c
@@ -2070,7 +2070,10 @@ static int __bind(struct mapped_device *
return 0;
}
-static void __unbind(struct mapped_device *md)
+/*
+ * Returns unbound table for the caller to free.
+ */
+struct dm_table *__unbind(struct mapped_device *md)
{
struct dm_table *map = md->map;
unsigned long flags;
@@ -2082,7 +2085,8 @@ static void __unbind(struct mapped_devic
write_lock_irqsave(&md->map_lock, flags);
md->map = NULL;
write_unlock_irqrestore(&md->map_lock, flags);
- dm_table_destroy(map);
+
+ return map;
}
/*
@@ -2175,7 +2179,7 @@ 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);
}
}
@@ -2381,8 +2385,9 @@ int dm_swap_table(struct mapped_device *
goto out;
}
- __unbind(md);
+ map = __unbind(md);
r = __bind(md, table, &limits);
+ dm_table_destroy(map);
out:
mutex_unlock(&md->suspend_lock);
--
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