linux-kernel - [PATCH 05/11] scsi: isci: port: link up: Pass gfp

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Date:   Fri, 18 Dec 2020 21:43:48 +0100
From:   "Ahmed S. Darwish" <a.darwish@...utronix.de>
To:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Daniel Wagner <dwagner@...e.de>,
        Jason Yan <yanaijie@...wei.com>,
        John Garry <john.garry@...wei.com>,
        Artur Paszkiewicz <artur.paszkiewicz@...el.com>,
        Jack Wang <jinpu.wang@...ud.ionos.com>
Cc:     linux-scsi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Sebastian A. Siewior" <bigeasy@...utronix.de>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>
Subject: [PATCH 05/11] scsi: isci: port: link up: Pass gfp_t flags

Use the new libsas event notifiers API, which requires callers to
explicitly pass the gfp_t memory allocation flags.

The libsas ->notify_port_event() hook is called from
isci_port_link_up().  Below is the context analysis for all of its call
chains:

host.c: isci_host_init()                                        (@)
spin_lock_irq(isci_host::scic_lock)
  -> sci_controller_initialize(), atomic                        (*)
    -> port_config.c: sci_port_configuration_agent_initialize()
      -> sci_mpc_agent_validate_phy_configuration()
        -> port.c: sci_port_add_phy()
          -> sci_port_general_link_up_handler()
            -> sci_port_activate_phy()
              -> isci_port_link_up()

port_config.c: apc_agent_timeout(), atomic, timer callback      (*)
  -> sci_apc_agent_configure_ports()
    -> port.c: sci_port_add_phy()
      -> sci_port_general_link_up_handler()
        -> sci_port_activate_phy()
          -> isci_port_link_up()

phy.c: enter SCI state: *SCI_PHY_SUB_FINAL*                     # Cont. from [1]
  -> phy.c: sci_phy_starting_final_substate_enter()
    -> phy.c: sci_change_state(SCI_PHY_READY)
      -> enter SCI state: *SCI_PHY_READY*
        -> phy.c: sci_phy_ready_state_enter()
          -> host.c: sci_controller_link_up()
            -> .link_up_handler()
            == port_config.c: sci_apc_agent_link_up()
              -> port.c: sci_port_link_up()
                -> (continue at [A])
            == port_config.c: sci_mpc_agent_link_up()
	      -> port.c: sci_port_link_up()
                -> (continue at [A])

port_config.c: mpc_agent_timeout(), atomic, timer callback      (*)
spin_lock_irqsave(isci_host::scic_lock, )
  -> ->link_up_handler()
  == port_config.c: sci_apc_agent_link_up()
    -> port.c: sci_port_link_up()
      -> (continue at [A])
  == port_config.c: sci_mpc_agent_link_up()
    -> port.c: sci_port_link_up()
      -> (continue at [A])

[A] port.c: sci_port_link_up()
  -> sci_port_activate_phy()
    -> isci_port_link_up()
  -> sci_port_general_link_up_handler()
    -> sci_port_activate_phy()
      -> isci_port_link_up()

[1] Call chains for entering SCI state: *SCI_PHY_SUB_FINAL*
-----------------------------------------------------------

host.c: power_control_timeout(), atomic, timer callback         (*)
spin_lock_irqsave(isci_host::scic_lock, )
  -> phy.c: sci_phy_consume_power_handler()
    -> phy.c: sci_change_state(SCI_PHY_SUB_FINAL)

host.c: sci_controller_error_handler(): atomic, irq handler     (*)
OR host.c: sci_controller_completion_handler(), atomic, tasklet (*)
  -> sci_controller_process_completions()
    -> sci_controller_unsolicited_frame()
      -> phy.c: sci_phy_frame_handler()
        -> sci_change_state(SCI_PHY_SUB_AWAIT_SAS_POWER)
          -> sci_phy_starting_await_sas_power_substate_enter()
            -> host.c: sci_controller_power_control_queue_insert()
              -> phy.c: sci_phy_consume_power_handler()
                -> sci_change_state(SCI_PHY_SUB_FINAL)
        -> sci_change_state(SCI_PHY_SUB_FINAL)
    -> sci_controller_event_completion()
      -> phy.c: sci_phy_event_handler()
        -> sci_phy_start_sata_link_training()
          -> sci_change_state(SCI_PHY_SUB_AWAIT_SATA_POWER)
            -> sci_phy_starting_await_sata_power_substate_enter
              -> host.c: sci_controller_power_control_queue_insert()
                -> phy.c: sci_phy_consume_power_handler()
                  -> sci_change_state(SCI_PHY_SUB_FINAL)

As can be seen from the "(*)" markers above, all the call-chains are
atomic.  Pass GFP_ATOMIC to libsas port event notifier.

Note, the now-replaced libsas APIs used in_interrupt() to implicitly
decide which memory allocation type to use.  This was only partially
correct, as it fails to choose the correct GFP flags when just
preemption or interrupts are disabled. Such buggy code paths are marked
with "(@)" in the call chains above.

Signed-off-by: Ahmed S. Darwish <a.darwish@...utronix.de>
Cc: stable@...r.kernel.org
Cc: Artur Paszkiewicz <artur.paszkiewicz@...el.com>
---
 drivers/scsi/isci/port.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/isci/port.c b/drivers/scsi/isci/port.c
index c3a8c84b19a2..69684c80c407 100644
--- a/drivers/scsi/isci/port.c
+++ b/drivers/scsi/isci/port.c
@@ -223,8 +223,9 @@ static void isci_port_link_up(struct isci_host *isci_host,
 	/* Notify libsas that we have an address frame, if indeed
 	 * we've found an SSP, SMP, or STP target */
 	if (success)
-		isci_host->sas_ha.notify_port_event(&iphy->sas_phy,
-						    PORTE_BYTES_DMAED);
+		isci_host->sas_ha.notify_port_event_gfp(&iphy->sas_phy,
+							PORTE_BYTES_DMAED,
+							GFP_ATOMIC);
 }
 
 
-- 
2.29.2