Hello Bart,
On 02/22/13 19:47, Bart Van Assche wrote:
> As the comment above rq_completed() explains, md members must
> not be touched after the dm_put() at the end of that function
> has been invoked. Avoid that the md->queue can be run
> asynchronously after the last md reference has been dropped by
> running that queue synchronously. This patch fixes the
> following kernel oops:
Calling blk_run_queue_async() there should be ok.
After dm_put(), the dm device may be removed. But free_dev() in dm.c
calls blk_queue_cleanup() and it should solve the race vs. delayed work.
And I could reproduce very similar oops without removing dm device
by following procedure:
(please replace "mpathX" with your dm-multipath map name)
# t=`dmsetup table mpathX`
# while sleep 1; do \
echo "$t" | dmsetup load mpathX; dmsetup resume mpathX; done
Looking at the following back trace:
> general protection fault: 0000 [#1] SMP
> RIP: 0010:[<ffffffff810fe754>] [<ffffffff810fe754>] mempool_free+0x24/0xb0
> Call Trace:
> <IRQ>
> [<ffffffff81187417>] bio_put+0x97/0xc0
> [<ffffffffa02247a5>] end_clone_bio+0x35/0x90 [dm_mod]
> [<ffffffff81185efd>] bio_endio+0x1d/0x30
> [<ffffffff811f03a3>] req_bio_endio.isra.51+0xa3/0xe0
> [<ffffffff811f2f68>] blk_update_request+0x118/0x520
> [<ffffffff811f3397>] blk_update_bidi_request+0x27/0xa0
> [<ffffffff811f343c>] blk_end_bidi_request+0x2c/0x80
> [<ffffffff811f34d0>] blk_end_request+0x10/0x20
> [<ffffffffa000b32b>] scsi_io_completion+0xfb/0x6c0 [scsi_mod]
> [<ffffffffa000107d>] scsi_finish_command+0xbd/0x120 [scsi_mod]
> [<ffffffffa000b12f>] scsi_softirq_done+0x13f/0x160 [scsi_mod]
> [<ffffffff811f9fd0>] blk_done_softirq+0x80/0xa0
> [<ffffffff81044551>] __do_softirq+0xf1/0x250
> [<ffffffff8142ee8c>] call_softirq+0x1c/0x30
> [<ffffffff8100420d>] do_softirq+0x8d/0xc0
> [<ffffffff81044885>] irq_exit+0xd5/0xe0
> [<ffffffff8142f3e3>] do_IRQ+0x63/0xe0
> [<ffffffff814257af>] common_interrupt+0x6f/0x6f
> <EOI>
> [<ffffffffa021737c>] srp_queuecommand+0x8c/0xcb0 [ib_srp]
> [<ffffffffa0002f18>] scsi_dispatch_cmd+0x148/0x310 [scsi_mod]
> [<ffffffffa000a38e>] scsi_request_fn+0x31e/0x520 [scsi_mod]
> [<ffffffff811f1e57>] __blk_run_queue+0x37/0x50
> [<ffffffff811f1f69>] blk_delay_work+0x29/0x40
> [<ffffffff81059003>] process_one_work+0x1c3/0x5c0
> [<ffffffff8105b22e>] worker_thread+0x15e/0x440
> [<ffffffff8106164b>] kthread+0xdb/0xe0
> [<ffffffff8142db9c>] ret_from_fork+0x7c/0xb0
it seems that the bioset was removed while being referenced.
c0820cf5 "dm: introduce per_bio_data" started to replace dm bioset
during table replacement because the size of bioset front_pad might
change for bio-based dm.
However, for request-based dm, it is not necessary because the size
of front_pad is static. Also we can't simply replace bioset because
prep-ed requests in queue have reference to the old bioset.
The patch below changes it not to replace bioset for request-based dm.
(Brings back to the same behavior with v3.7)
With this patch, I could not reproduce the problem.
Could you try this?
--
Jun'ichi Nomura, NEC Corporation
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 314a0e2..51fefb5 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1973,15 +1973,27 @@ static void __bind_mempools(struct mapped_device *md, struct dm_table *t)
{
struct dm_md_mempools *p = dm_table_get_md_mempools(t);
- if (md->io_pool && (md->tio_pool || dm_table_get_type(t) == DM_TYPE_BIO_BASED) && md->bs) {
- /*
- * The md already has necessary mempools. Reload just the
- * bioset because front_pad may have changed because
- * a different table was loaded.
- */
- bioset_free(md->bs);
- md->bs = p->bs;
- p->bs = NULL;
+ if (md->io_pool && md->bs) {
+ /* The md already has necessary mempools. */
+ if (dm_table_get_type(t) == DM_TYPE_BIO_BASED) {
+ /*
+ * Reload bioset because front_pad may have changed
+ * because a different table was loaded.
+ */
+ bioset_free(md->bs);
+ md->bs = p->bs;
+ p->bs = NULL;
+ } else if (dm_table_get_type(t) == DM_TYPE_REQUEST_BASED) {
+ BUG_ON(!md->tio_pool);
+ /*
+ * No need to reload in case of request-based dm
+ * because of fixed size front_pad.
+ * Note for future: if you are to reload bioset,
+ * prep-ed requests in queue may have reference
+ * to bio from the old bioset.
+ * So you must walk through the queue to unprep.
+ */
+ }
goto out;
}
--
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