The map_context pointer should always be set. However, we
have reports that upon requeing it is not set correctly.
So add a BUG_ON() statement and clear the pointer to
track the issue properly.

Cc: Alasdair Kergon <akg@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Dave Wysochanski <dwysocha@redhat.com>
---
drivers/md/dm-mpath.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 801d92d..94a91d6 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -920,8 +920,10 @@ static int multipath_map(struct dm_target *ti, struct request *clone,
map_context->ptr = mpio;
clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
r = map_io(m, clone, mpio, 0);
- if (r < 0 || r == DM_MAPIO_REQUEUE)
+ if (r < 0 || r == DM_MAPIO_REQUEUE) {
mempool_free(mpio, m->mpio_pool);
+ map_context->ptr = NULL;
+ }

return r;
}
@@ -1228,6 +1230,8 @@ static int do_end_io(struct multipath *m, struct request *clone,
int r = DM_ENDIO_REQUEUE;
unsigned long flags;

+ BUG_ON(!mpio);
+
if (!error && !clone->errors)
return 0; /* I/O complete */

--
1.6.0.2

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On Mon, Mar 19, 2012 at 04:15:28PM +0100, Hannes Reinecke wrote:
> - if (r < 0 || r == DM_MAPIO_REQUEUE)
> + if (r < 0 || r == DM_MAPIO_REQUEUE) {
> mempool_free(mpio, m->mpio_pool);
> + map_context->ptr = NULL;
> + }

What about the other places that do mempool_free() ?
Should they clear it too?

Is it better to swap the statement order - clear it *before*
freeing i

Alasdair

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