[PATCH AUTOSEL 5.6 148/606] scsi: target: Put lun_ref at end of tmr processing

Sasha Levin
2020-06-09T00:32:36Z

From: Bodo Stroesser <bstroesser@ts.fujitsu.com>

commit f2e6b75f6ee82308ef7b00f29e71e5f1c6b3d52a upstream.

Testing with Loopback I found that, after a Loopback LUN has executed a
TMR, I can no longer unlink the LUN. The rm command hangs in
transport_clear_lun_ref() at wait_for_completion(&lun->lun_shutdown_comp)
The reason is, that transport_lun_remove_cmd() is not called at the end of
target_tmr_work().

It seems, that in other fabrics this call happens implicitly when the
fabric drivers call transport_generic_free_cmd() during their
->queue_tm_rsp().

Unfortunately Loopback seems to not comply to the common way
of calling transport_generic_free_cmd() from ->queue_*().
Instead it calls transport_generic_free_cmd() from its
->check_stop_free() only.

But the ->check_stop_free() is called by
transport_cmd_check_stop_to_fabric() after it has reset the se_cmd->se_lun
pointer. Therefore the following transport_generic_free_cmd() skips the
transport_lun_remove_cmd().

So this patch re-adds the transport_lun_remove_cmd() at the end of
target_tmr_work(), which was removed during commit 2c9fa49e100f ("scsi:
target/core: Make ABORT and LUN RESET handling synchronous").

For fabrics using transport_generic_free_cmd() in the usual way the double
call to transport_lun_remove_cmd() doesn't harm, as
transport_lun_remove_cmd() checks for this situation and does not release
lun_ref twice.

Link: https://lore.kernel.org/r/20200513153443.3554-1-bstroesser@ts.fujitsu.com
Fixes: 2c9fa49e100f ("scsi: target/core: Make ABORT and LUN RESET handling synchronous")
Cc: stable@vger.kernel.org
Tested-by: Bryant G. Ly <bryangly@gmail.com>
Reviewed-by: Bart van Assche <bvanassche@acm.org>
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/target/target_core_transport.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 0ae9e60fc4d5..61486e5abee4 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3349,6 +3349,7 @@ static void target_tmr_work(struct work_struct *work)

cmd->se_tfo->queue_tm_rsp(cmd);

+ transport_lun_remove_cmd(cmd);
transport_cmd_check_stop_to_fabric(cmd);
return;

--
2.25.1