ata: libata-scsi: do not needlessly defer commands when using PMP with FBS

The ACS specification does not allow a non-NCQ command to be issued while
an NCQ command is outstanding.

Commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
introduced a feature where a deferred non-NCQ command gets issued from a
workqueue. The design stores a single non-NCQ command per port.

However, when using Port Multipliers (PMPs), specifically PMPs that
support FIS-Based Switching (FBS), non-NCQ and NCQ commands can be mixed
on the same port, just not for the same link, see e.g. ata_std_qc_defer()
which is, and always has operated on a per-link basis.

Therefore, move the deferred_qc from struct ata_port to struct ata_link.
This way, when using a PMP with FBS, we will not needlessly defer commands
to all other links, just because one link issued a non-NCQ command while
having an NCQ command outstanding. Only commands for that specific link
will be deferred. This is in line with how PMPs with FBS worked before
commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation").

Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
Tested-by: Tommy Kelly <linux@tkel.ly>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index e76d15411e2aee5fd87b5ffc82a6364274b0db1f..3d0027ec33c2a2730bc6eedced44af5041b67337 100644 (file)
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5584,6 +5584,7 @@ void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp)
        link->pmp = pmp;
        link->active_tag = ATA_TAG_POISON;
        link->hw_sata_spd_limit = UINT_MAX;
+       INIT_WORK(&link->deferred_qc_work, ata_scsi_deferred_qc_work);
 
        /* can't use iterator, ap isn't initialized yet */
        for (i = 0; i < ATA_MAX_DEVICES; i++) {
@@ -5666,7 +5667,6 @@ struct ata_port *ata_port_alloc(struct ata_host *host)
        mutex_init(&ap->scsi_scan_mutex);
        INIT_DELAYED_WORK(&ap->hotplug_task, ata_scsi_hotplug);
        INIT_DELAYED_WORK(&ap->scsi_rescan_task, ata_scsi_dev_rescan);
-       INIT_WORK(&ap->deferred_qc_work, ata_scsi_deferred_qc_work);
        INIT_LIST_HEAD(&ap->eh_done_q);
        init_waitqueue_head(&ap->eh_wait_q);
        init_completion(&ap->park_req_pending);
@@ -6291,12 +6291,15 @@ static void ata_port_detach(struct ata_port *ap)
 
        /* It better be dead now and not have any remaining deferred qc. */
        WARN_ON(!(ap->pflags & ATA_PFLAG_UNLOADED));
-       WARN_ON(ap->deferred_qc);
 
-       cancel_work_sync(&ap->deferred_qc_work);
        cancel_delayed_work_sync(&ap->hotplug_task);
        cancel_delayed_work_sync(&ap->scsi_rescan_task);
 
+       ata_for_each_link(link, ap, PMP_FIRST) {
+               WARN_ON(link->deferred_qc);
+               cancel_work_sync(&link->deferred_qc_work);
+       }
+
        /* Delete port multiplier link transport devices */
        if (ap->pmp_link) {
                int i;

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 9a4b67b90b17b665382cca2d04c73d533426a5ce..d623eb32ed8b7b2fb141e0adbd2cdeb53cd5d115 100644 (file)
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -651,11 +651,11 @@ int ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
                        if (qc->scsicmd != scmd)
                                continue;
                        if ((qc->flags & ATA_QCFLAG_ACTIVE) ||
-                           qc == ap->deferred_qc)
+                           qc == qc->dev->link->deferred_qc)
                                break;
                }
 
-               if (i < ATA_MAX_QUEUE && qc == ap->deferred_qc) {
+               if (i < ATA_MAX_QUEUE && qc == qc->dev->link->deferred_qc) {
                        /*
                         * This is a deferred command that timed out while
                         * waiting for the command queue to drain. Since the qc
@@ -666,8 +666,8 @@ int ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
                         * deferred qc work from issuing this qc.
                         */
                        WARN_ON_ONCE(qc->flags & ATA_QCFLAG_ACTIVE);
-                       ap->deferred_qc = NULL;
-                       cancel_work(&ap->deferred_qc_work);
+                       qc->dev->link->deferred_qc = NULL;
+                       cancel_work(&qc->dev->link->deferred_qc_work);
                        set_host_byte(scmd, DID_TIME_OUT);
                        scsi_eh_finish_cmd(scmd, &ap->eh_done_q);
                } else if (i < ATA_MAX_QUEUE) {

diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index 7e889534d73b469d580e7d5ddc32e55b0733767b..e8540931b4a117f8b97d88738d98b0dd6d0ae7f2 100644 (file)
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -582,8 +582,11 @@ static void sata_pmp_detach(struct ata_device *dev)
        if (ap->ops->pmp_detach)
                ap->ops->pmp_detach(ap);
 
-       ata_for_each_link(tlink, ap, EDGE)
+       ata_for_each_link(tlink, ap, EDGE) {
+               WARN_ON(tlink->deferred_qc);
+               cancel_work_sync(&tlink->deferred_qc_work);
                ata_eh_detach_dev(tlink->device);
+       }
 
        spin_lock_irqsave(ap->lock, flags);
        ap->nr_pmp_links = 0;

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index ca29744c57f92445cceb440f9e3cf242eecf03d4..d43207c6e4679d65b4241021bc1177a51232872e 100644 (file)
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1664,8 +1664,9 @@ static void ata_scsi_qc_done(struct ata_queued_cmd *qc, bool set_result,
 
 void ata_scsi_deferred_qc_work(struct work_struct *work)
 {
-       struct ata_port *ap =
-               container_of(work, struct ata_port, deferred_qc_work);
+       struct ata_link *link =
+               container_of(work, struct ata_link, deferred_qc_work);
+       struct ata_port *ap = link->ap;
        struct ata_queued_cmd *qc;
        unsigned long flags;
 
@@ -1676,10 +1677,10 @@ void ata_scsi_deferred_qc_work(struct work_struct *work)
         * such case, we should not need any more deferring the qc, so warn if
         * qc_defer() says otherwise.
         */
-       qc = ap->deferred_qc;
+       qc = link->deferred_qc;
        if (qc && !ata_port_eh_scheduled(ap)) {
                WARN_ON_ONCE(ap->ops->qc_defer(qc));
-               ap->deferred_qc = NULL;
+               link->deferred_qc = NULL;
                ata_qc_issue(qc);
        }
 
@@ -1688,7 +1689,7 @@ void ata_scsi_deferred_qc_work(struct work_struct *work)
 
 void ata_scsi_requeue_deferred_qc(struct ata_port *ap)
 {
-       struct ata_queued_cmd *qc = ap->deferred_qc;
+       struct ata_link *link;
 
        lockdep_assert_held(ap->lock);
 
@@ -1697,16 +1698,21 @@ void ata_scsi_requeue_deferred_qc(struct ata_port *ap)
         * do not try to be smart about what to do with this deferred command
         * and simply requeue it by completing it with DID_REQUEUE.
         */
-       if (qc) {
-               ap->deferred_qc = NULL;
-               cancel_work(&ap->deferred_qc_work);
-               ata_scsi_qc_done(qc, true, DID_REQUEUE << 16);
+       ata_for_each_link(link, ap, PMP_FIRST) {
+               struct ata_queued_cmd *qc = link->deferred_qc;
+
+               if (qc) {
+                       link->deferred_qc = NULL;
+                       cancel_work(&link->deferred_qc_work);
+                       ata_scsi_qc_done(qc, true, DID_REQUEUE << 16);
+               }
        }
 }
 
-static void ata_scsi_schedule_deferred_qc(struct ata_port *ap)
+static void ata_scsi_schedule_deferred_qc(struct ata_link *link)
 {
-       struct ata_queued_cmd *qc = ap->deferred_qc;
+       struct ata_queued_cmd *qc = link->deferred_qc;
+       struct ata_port *ap = link->ap;
 
        lockdep_assert_held(ap->lock);
 
@@ -1723,12 +1729,12 @@ static void ata_scsi_schedule_deferred_qc(struct ata_port *ap)
                return;
        }
        if (!ap->ops->qc_defer(qc))
-               queue_work(system_highpri_wq, &ap->deferred_qc_work);
+               queue_work(system_highpri_wq, &link->deferred_qc_work);
 }
 
 static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
 {
-       struct ata_port *ap = qc->ap;
+       struct ata_link *link = qc->dev->link;
        struct scsi_cmnd *cmd = qc->scsicmd;
        u8 *cdb = cmd->cmnd;
        bool have_sense = qc->flags & ATA_QCFLAG_SENSE_VALID;
@@ -1759,11 +1765,12 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
 
        ata_scsi_qc_done(qc, false, 0);
 
-       ata_scsi_schedule_deferred_qc(ap);
+       ata_scsi_schedule_deferred_qc(link);
 }
 
 static int ata_scsi_qc_issue(struct ata_port *ap, struct ata_queued_cmd *qc)
 {
+       struct ata_link *link = qc->dev->link;
        int ret;
 
        if (!ap->ops->qc_defer)
@@ -1774,7 +1781,7 @@ static int ata_scsi_qc_issue(struct ata_port *ap, struct ata_queued_cmd *qc)
         * requeue and defer all incoming commands until the deferred qc is
         * processed, once all on-going commands complete.
         */
-       if (ap->deferred_qc) {
+       if (link->deferred_qc) {
                ata_qc_free(qc);
                return SCSI_MLQUEUE_DEVICE_BUSY;
        }
@@ -1790,8 +1797,8 @@ static int ata_scsi_qc_issue(struct ata_port *ap, struct ata_queued_cmd *qc)
        case ATA_DEFER_LINK_EXCL:
                /*
                 * Drivers making use of ap->excl_link cannot store the QC in
-                * ap->deferred_qc, because the ap->excl_link handling is
-                * incompatible with the ap->deferred_qc workqueue handling.
+                * link->deferred_qc, because the ap->excl_link handling is
+                * incompatible with the link->deferred_qc workqueue handling.
                 */
                ret = SCSI_MLQUEUE_DEVICE_BUSY;
                goto free_qc;
@@ -1817,7 +1824,7 @@ defer_qc:
         * commands complete.
         */
        if (!ata_is_ncq(qc->tf.protocol)) {
-               ap->deferred_qc = qc;
+               link->deferred_qc = qc;
                return 0;
        }
 

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 360776016b506a2ed2f677df33818859a2c22d5d..127229fbd1a632d1ec1216635d64767f11e252e7 100644 (file)
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -855,6 +855,9 @@ struct ata_link {
        unsigned int            sata_spd;       /* current SATA PHY speed */
        enum ata_lpm_policy     lpm_policy;
 
+       struct work_struct      deferred_qc_work;
+       struct ata_queued_cmd   *deferred_qc;
+
        /* record runtime error info, protected by host_set lock */
        struct ata_eh_info      eh_info;
        /* EH context */
@@ -900,9 +903,6 @@ struct ata_port {
        u64                     qc_active;
        int                     nr_active_links; /* #links with active qcs */
 
-       struct work_struct      deferred_qc_work;
-       struct ata_queued_cmd   *deferred_qc;
-
        struct ata_link         link;           /* host default link */
        struct ata_link         *slave_link;    /* see ata_slave_link_init() */