Acked-by: Mikulas Patocka <mpato...@redhat.com>
On Tue, 26 Feb 2013, Jun'ichi Nomura wrote:
> This patch fixes a regression introduced in v3.8, which causes oops
> like this when dm-multipath is used:
>
> 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
>
> The regression was introduced by the change
> c0820cf5 "dm: introduce per_bio_data", where dm started to replace
> bioset during table replacement.
> For bio-based dm, it is good because clone bios do not exist during the
> table replacement.
> For request-based dm, however, (not-yet-mapped) clone bios may stay in
> request queue and survive during the table replacement.
> So freeing the old bioset could cause the oops in bio_put().
>
> Since the size of front_pad may change only with bio-based dm,
> it is not necessary to replace bioset for request-based dm.
>
> Reported-by: Bart Van Assche <bvanass...@acm.org>
> Tested-by: Bart Van Assche <bvanass...@acm.org>
> Signed-off-by: Jun'ichi Nomura <j-nom...@ce.jp.nec.com>
> Cc: Alasdair G Kergon <a...@redhat.com>
> Cc: Mikulas Patocka <mpato...@redhat.com>
> Cc: Mike Snitzer <snit...@redhat.com>
> Cc: <sta...@vger.kernel.org>
> ---
> drivers/md/dm.c | 30 +++++++++++++++++++++---------
> 1 file changed, 21 insertions(+), 9 deletions(-)
>
> 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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