[PATCH] libata-hp: implement hotplug

Implement ATA part of hotplug.  To avoid probing broken devices over
and over again, disabled devices are not automatically detached.  They
are detached only if probing is requested for the device or the
associated port is offline.  Also, to avoid infinite probing loop,
Each device is probed only once per EH run.

As SATA PHY status is fragile, devices are detached only after it has
used up its recovery chances unless explicitly requested by LLDD or
user (LLDD may request direct detach if, for example, it supports cold
presence detection).
Signed-off-by: Tejun Heo <htejun@gmail.com>

drivers/scsi/libata-eh.c

@@ -932,10 +932,8 @@ static void ata_eh_analyze_serror(struct ata_port *ap)
 		err_mask |= AC_ERR_SYSTEM;
 		action |= ATA_EH_SOFTRESET;
 	}
-	if (serror & (SERR_PHYRDY_CHG | SERR_DEV_XCHG)) {
-		err_mask |= AC_ERR_ATA_BUS;
-		action |= ATA_EH_HARDRESET;
-	}
+	if (serror & (SERR_PHYRDY_CHG | SERR_DEV_XCHG))
+		ata_ehi_hotplugged(&ehc->i);
 
 	ehc->i.err_mask |= err_mask;
 	ehc->i.action |= action;
@@ -1487,11 +1485,12 @@ static int ata_eh_reset(struct ata_port *ap, int classify,
 	return rc;
 }
 
-static int ata_eh_revalidate(struct ata_port *ap,
+static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 					struct ata_device **r_failed_dev)
 {
 	struct ata_eh_context *ehc = &ap->eh_context;
 	struct ata_device *dev;
+	unsigned long flags;
 	int i, rc = 0;
 
 	DPRINTK("ENTER\n");
@@ -1513,6 +1512,23 @@ static int ata_eh_revalidate(struct ata_port *ap,
 				break;
 
 			ehc->i.action &= ~ATA_EH_REVALIDATE;
+		} else if (dev->class == ATA_DEV_UNKNOWN &&
+			   ehc->tries[dev->devno] &&
+			   ata_class_enabled(ehc->classes[dev->devno])) {
+			dev->class = ehc->classes[dev->devno];
+
+			rc = ata_dev_read_id(dev, &dev->class, 1, dev->id);
+			if (rc == 0)
+				rc = ata_dev_configure(dev, 1);
+
+			if (rc) {
+				dev->class = ATA_DEV_UNKNOWN;
+				break;
+			}
+
+			spin_lock_irqsave(&ap->host_set->lock, flags);
+			ap->flags |= ATA_FLAG_SCSI_HOTPLUG;
+			spin_unlock_irqrestore(&ap->host_set->lock, flags);
 		}
 	}
 
@@ -1533,6 +1549,36 @@ static int ata_port_nr_enabled(struct ata_port *ap)
 	return cnt;
 }
 
+static int ata_port_nr_vacant(struct ata_port *ap)
+{
+	int i, cnt = 0;
+
+	for (i = 0; i < ATA_MAX_DEVICES; i++)
+		if (ap->device[i].class == ATA_DEV_UNKNOWN)
+			cnt++;
+	return cnt;
+}
+
+static int ata_eh_skip_recovery(struct ata_port *ap)
+{
+	struct ata_eh_context *ehc = &ap->eh_context;
+	int i;
+
+	if (ap->flags & ATA_FLAG_FROZEN || ata_port_nr_enabled(ap))
+		return 0;
+
+	/* skip if class codes for all vacant slots are ATA_DEV_NONE */
+	for (i = 0; i < ATA_MAX_DEVICES; i++) {
+		struct ata_device *dev = &ap->device[i];
+
+		if (dev->class == ATA_DEV_UNKNOWN &&
+		    ehc->classes[dev->devno] != ATA_DEV_NONE)
+			return 0;
+	}
+
+	return 1;
+}
+
 /**
  *	ata_eh_recover - recover host port after error
  *	@ap: host port to recover
@@ -1543,9 +1589,10 @@ static int ata_port_nr_enabled(struct ata_port *ap)
  *
  *	This is the alpha and omega, eum and yang, heart and soul of
  *	libata exception handling.  On entry, actions required to
- *	recover each devices are recorded in eh_context.  This
- *	function executes all the operations with appropriate retrials
- *	and fallbacks to resurrect failed devices.
+ *	recover the port and hotplug requests are recorded in
+ *	eh_context.  This function executes all the operations with
+ *	appropriate retrials and fallbacks to resurrect failed
+ *	devices, detach goners and greet newcomers.
  *
  *	LOCKING:
  *	Kernel thread context (may sleep).
@@ -1568,6 +1615,19 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 		dev = &ap->device[i];
 
 		ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;
+
+		/* process hotplug request */
+		if (dev->flags & ATA_DFLAG_DETACH)
+			ata_eh_detach_dev(dev);
+
+		if (!ata_dev_enabled(dev) &&
+		    ((ehc->i.probe_mask & (1 << dev->devno)) &&
+		     !(ehc->did_probe_mask & (1 << dev->devno)))) {
+			ata_eh_detach_dev(dev);
+			ata_dev_init(dev);
+			ehc->did_probe_mask |= (1 << dev->devno);
+			ehc->i.action |= ATA_EH_SOFTRESET;
+		}
 	}
 
  retry:
@@ -1575,15 +1635,18 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 	rc = 0;
 
 	/* skip EH if possible. */
-	if (!ata_port_nr_enabled(ap) && !(ap->flags & ATA_FLAG_FROZEN))
+	if (ata_eh_skip_recovery(ap))
 		ehc->i.action = 0;
 
+	for (i = 0; i < ATA_MAX_DEVICES; i++)
+		ehc->classes[i] = ATA_DEV_UNKNOWN;
+
 	/* reset */
 	if (ehc->i.action & ATA_EH_RESET_MASK) {
 		ata_eh_freeze_port(ap);
 
-		rc = ata_eh_reset(ap, 0, prereset, softreset, hardreset,
-				  postreset);
+		rc = ata_eh_reset(ap, ata_port_nr_vacant(ap), prereset,
+				  softreset, hardreset, postreset);
 		if (rc) {
 			ata_port_printk(ap, KERN_ERR,
 					"reset failed, giving up\n");
@@ -1593,8 +1656,8 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 		ata_eh_thaw_port(ap);
 	}
 
-	/* revalidate existing devices */
-	rc = ata_eh_revalidate(ap, &dev);
+	/* revalidate existing devices and attach new ones */
+	rc = ata_eh_revalidate_and_attach(ap, &dev);
 	if (rc)
 		goto dev_fail;
 
@@ -1612,6 +1675,8 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
  dev_fail:
 	switch (rc) {
 	case -ENODEV:
+		/* device missing, schedule probing */
+		ehc->i.probe_mask |= (1 << dev->devno);
 	case -EINVAL:
 		ehc->tries[dev->devno] = 0;
 		break;
@@ -1624,15 +1689,31 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 			ehc->tries[dev->devno] = 0;
 	}
 
+	if (ata_dev_enabled(dev) && !ehc->tries[dev->devno]) {
 		/* disable device if it has used up all its chances */
-	if (ata_dev_enabled(dev) && !ehc->tries[dev->devno])
 		ata_dev_disable(dev);
 
+		/* detach if offline */
+		if (ata_port_offline(ap))
+			ata_eh_detach_dev(dev);
+
+		/* probe if requested */
+		if ((ehc->i.probe_mask & (1 << dev->devno)) &&
+		    !(ehc->did_probe_mask & (1 << dev->devno))) {
+			ata_eh_detach_dev(dev);
+			ata_dev_init(dev);
+
+			ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;
+			ehc->did_probe_mask |= (1 << dev->devno);
+			ehc->i.action |= ATA_EH_SOFTRESET;
+		}
+	} else {
 		/* soft didn't work?  be haaaaard */
 		if (ehc->i.flags & ATA_EHI_DID_RESET)
 			ehc->i.action |= ATA_EH_HARDRESET;
 		else
 			ehc->i.action |= ATA_EH_SOFTRESET;
+	}
 
 	if (ata_port_nr_enabled(ap)) {
 		ata_port_printk(ap, KERN_WARNING, "failed to recover some "

include/linux/libata.h

@@ -824,6 +824,19 @@ extern void ata_do_eh(struct ata_port *ap, ata_prereset_fn_t prereset,
 	(ehi)->desc_len = 0; \
 } while (0)
 
+static inline void ata_ehi_hotplugged(struct ata_eh_info *ehi)
+{
+	if (ehi->flags & ATA_EHI_HOTPLUGGED)
+		return;
+
+	ehi->flags |= ATA_EHI_HOTPLUGGED;
+	ehi->hotplug_timestamp = jiffies;
+
+	ehi->err_mask |= AC_ERR_ATA_BUS;
+	ehi->action |= ATA_EH_SOFTRESET;
+	ehi->probe_mask |= (1 << ATA_MAX_DEVICES) - 1;
+}
+
 /*
  * qc helpers
  */