scsi: target: put lun_ref at end of tmr processing

Commit Message

Bodo Stroesser May 12, 2020, 4:17 p.m. UTC

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
2c9fa49e100f962af988f1c0529231bf14905cda
"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.

Signed-off-by: Bodo Stroesser <[e-mail]>
Tested-by: Bryant G. Ly <[e-mail]>
---
 drivers/target/target_core_transport.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Bart Van Assche May 12, 2020, 11:05 p.m. UTC | #1

On 2020-05-12 09:17, Bodo Stroesser wrote:
> 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
> 2c9fa49e100f962af988f1c0529231bf14905cda
> "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.
> 
> Signed-off-by: Bodo Stroesser <[e-mail]>
> Tested-by: Bryant G. Ly <[e-mail]>

Please add Fixes: ... and Cc: stable tags. Anyway:

Reviewed-by: Bart van Assche <[e-mail]>

Patch

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 594b724bbf79..264a822c0bfa 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3350,6 +3350,7 @@  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;