libata: improve EH retry delay handling

EH retries were delayed by 5 seconds to ensure that resets don't occur
back-to-back.  However, this 5 second delay is superflous or excessive
in many cases.  For example, after IDENTIFY times out, there's no
reason to wait five more seconds before retrying.

This patch adds ehc->last_reset timestamp and record the timestamp for
the last reset trial or success and uses it to space resets by
ATA_EH_RESET_COOL_DOWN which is 5 secs and removes unconditional 5 sec
sleeps.

As this change makes inter-try waits often shorter and they're
redundant in nature, this patch also removes the "retrying..."
messages.

While at it, convert explicit rounding up division to DIV_ROUND_UP().

This change speeds up EH in many cases w/o sacrificing robustness.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

3 files changed, 22 insertions, 28 deletions

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 08dd07f10008..5b5ae631ed03 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -67,6 +67,9 @@ enum {
         ATA_ECAT_DUBIOUS_UNK_DEV        = 7,
         ATA_ECAT_NR                     = 8,
 
+        /* always put at least this amount of time between resets */
+        ATA_EH_RESET_COOL_DOWN          =  5000,
+
         /* Waiting in ->prereset can never be reliable.  It's
          * sometimes nice to wait there but it can't be depended upon;
          * otherwise, we wouldn't be resetting.  Just give it enough
@@ -485,6 +488,9 @@ void ata_scsi_error(struct Scsi_Host *host)
                                 if (ata_ncq_enabled(dev))
                                         ehc->saved_ncq_enabled |= 1 << devno;
                         }
+
+                        /* set last reset timestamp to some time in the past */
+                        ehc->last_reset = jiffies - 60 * HZ;
                 }
 
                 ap->pflags |= ATA_PFLAG_EH_IN_PROGRESS;
@@ -2088,11 +2094,17 @@ int ata_eh_reset(struct ata_link *link, int classify,
         /*
          * Prepare to reset
          */
+        now = jiffies;
+        deadline = ata_deadline(ehc->last_reset, ATA_EH_RESET_COOL_DOWN);
+        if (time_before(now, deadline))
+                schedule_timeout_uninterruptible(deadline - now);
+
         spin_lock_irqsave(ap->lock, flags);
         ap->pflags |= ATA_PFLAG_RESETTING;
         spin_unlock_irqrestore(ap->lock, flags);
 
         ata_eh_about_to_do(link, NULL, ATA_EH_RESET);
+        ehc->last_reset = jiffies;
 
         ata_link_for_each_dev(dev, link) {
                 /* If we issue an SRST then an ATA drive (not ATAPI)
@@ -2158,6 +2170,7 @@ int ata_eh_reset(struct ata_link *link, int classify,
         /*
          * Perform reset
          */
+        ehc->last_reset = jiffies;
         if (ata_is_host_link(link))
                 ata_eh_freeze_port(ap);
 
@@ -2278,6 +2291,7 @@ int ata_eh_reset(struct ata_link *link, int classify,
 
         /* reset successful, schedule revalidation */
         ata_eh_done(link, NULL, ATA_EH_RESET);
+        ehc->last_reset = jiffies;
         ehc->i.action |= ATA_EH_REVALIDATE;
 
         rc = 0;
@@ -2304,9 +2318,9 @@ int ata_eh_reset(struct ata_link *link, int classify,
         if (time_before(now, deadline)) {
                 unsigned long delta = deadline - now;
 
-                ata_link_printk(link, KERN_WARNING, "reset failed "
-                                "(errno=%d), retrying in %u secs\n",
-                                rc, (jiffies_to_msecs(delta) + 999) / 1000);
+                ata_link_printk(link, KERN_WARNING,
+                        "reset failed (errno=%d), retrying in %u secs\n",
+                        rc, DIV_ROUND_UP(jiffies_to_msecs(delta), 1000));
 
                 while (delta)
                         delta = schedule_timeout_uninterruptible(delta);
@@ -2623,7 +2637,7 @@ int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 {
         struct ata_link *link;
         struct ata_device *dev;
-        int nr_failed_devs, nr_disabled_devs;
+        int nr_failed_devs;
         int rc;
         unsigned long flags;
 
@@ -2666,7 +2680,6 @@ int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
  retry:
         rc = 0;
         nr_failed_devs = 0;
-        nr_disabled_devs = 0;
 
         /* if UNLOADING, finish immediately */
         if (ap->pflags & ATA_PFLAG_UNLOADING)
@@ -2733,8 +2746,7 @@ int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 
 dev_fail:
                 nr_failed_devs++;
-                if (ata_eh_handle_dev_fail(dev, rc))
-                        nr_disabled_devs++;
+                ata_eh_handle_dev_fail(dev, rc);
 
                 if (ap->pflags & ATA_PFLAG_FROZEN) {
                         /* PMP reset requires working host port.
@@ -2746,18 +2758,8 @@ dev_fail:
                 }
         }
 
-        if (nr_failed_devs) {
-                if (nr_failed_devs != nr_disabled_devs) {
-                        ata_port_printk(ap, KERN_WARNING, "failed to recover "
-                                        "some devices, retrying in 5 secs\n");
-                        ssleep(5);
-                } else {
-                        /* no device left to recover, repeat fast */
-                        msleep(500);
-                }
-
+        if (nr_failed_devs)
                 goto retry;
-        }
 
  out:
         if (rc && r_failed_link)
diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index 63691d77ac43..b65db309c181 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -727,19 +727,12 @@ static int sata_pmp_eh_recover_pmp(struct ata_port *ap,
                 }
 
                 if (tries) {
-                        int sleep = ehc->i.flags & ATA_EHI_DID_RESET;
-
                         /* consecutive revalidation failures? speed down */
                         if (reval_failed)
                                 sata_down_spd_limit(link);
                         else
                                 reval_failed = 1;
 
-                        ata_dev_printk(dev, KERN_WARNING,
-                                       "retrying reset%s\n",
-                                       sleep ? " in 5 secs" : "");
-                        if (sleep)
-                                ssleep(5);
                         ehc->i.action |= ATA_EH_RESET;
                         goto retry;
                 } else {
@@ -991,10 +984,7 @@ static int sata_pmp_eh_recover(struct ata_port *ap)
                 goto retry;
 
         if (--pmp_tries) {
-                ata_port_printk(ap, KERN_WARNING,
-                                "failed to recover PMP, retrying in 5 secs\n");
                 pmp_ehc->i.action |= ATA_EH_RESET;
-                ssleep(5);
                 goto retry;
         }
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 94110b652b30..9058c2a325a9 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -602,6 +602,8 @@ struct ata_eh_context {
         unsigned int            did_probe_mask;
         unsigned int            saved_ncq_enabled;
         u8                      saved_xfer_mode[ATA_MAX_DEVICES];
+        /* timestamp for the last reset attempt or success */
+        unsigned long           last_reset;
 };
 
 struct ata_acpi_drive