libata: clean up EH speed down implementation

Clean up EH speed down implementation.

* is_io boolean variable is replaced eflags.  is_io is ATA_EFLAG_IS_IO.

* Error categories now have names.

* Better comments.

* Reorder 5min and 10min rules in ata_eh_speed_down_verdict()

* Use local variable @link to cache @dev->link in ata_eh_speed_down()

These changes are to improve readability and ease further changes.
This patch doesn't introduce any behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

2 files changed, 74 insertions, 45 deletions

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index ebab75958900..b01ade102727 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -46,9 +46,20 @@
 #include "libata.h"
 
 enum {
+        /* speed down verdicts */
         ATA_EH_SPDN_NCQ_OFF             = (1 << 0),
         ATA_EH_SPDN_SPEED_DOWN          = (1 << 1),
         ATA_EH_SPDN_FALLBACK_TO_PIO     = (1 << 2),
+
+        /* error flags */
+        ATA_EFLAG_IS_IO                 = (1 << 0),
+
+        /* error categories */
+        ATA_ECAT_NONE                   = 0,
+        ATA_ECAT_ATA_BUS                = 1,
+        ATA_ECAT_TOUT_HSM               = 2,
+        ATA_ECAT_UNK_DEV                = 3,
+        ATA_ECAT_NR                     = 4,
 };
 
 /* Waiting in ->prereset can never be reliable.  It's sometimes nice
@@ -218,7 +229,7 @@ void ata_port_pbar_desc(struct ata_port *ap, int bar, ssize_t offset,
 
 #endif /* CONFIG_PCI */
 
-static void ata_ering_record(struct ata_ering *ering, int is_io,
+static void ata_ering_record(struct ata_ering *ering, unsigned int eflags,
                              unsigned int err_mask)
 {
         struct ata_ering_entry *ent;
@@ -229,7 +240,7 @@ static void ata_ering_record(struct ata_ering *ering, int is_io,
         ering->cursor %= ATA_ERING_SIZE;
 
         ent = &ering->ring[ering->cursor];
-        ent->is_io = is_io;
+        ent->eflags = eflags;
         ent->err_mask = err_mask;
         ent->timestamp = get_jiffies_64();
 }
@@ -1451,20 +1462,20 @@ static unsigned int ata_eh_analyze_tf(struct ata_queued_cmd *qc,
         return action;
 }
 
-static int ata_eh_categorize_error(int is_io, unsigned int err_mask)
+static int ata_eh_categorize_error(unsigned int eflags, unsigned int err_mask)
 {
         if (err_mask & AC_ERR_ATA_BUS)
-                return 1;
+                return ATA_ECAT_ATA_BUS;
 
         if (err_mask & AC_ERR_TIMEOUT)
-                return 2;
+                return ATA_ECAT_TOUT_HSM;
 
-        if (is_io) {
+        if (eflags & ATA_EFLAG_IS_IO) {
                 if (err_mask & AC_ERR_HSM)
-                        return 2;
+                        return ATA_ECAT_TOUT_HSM;
                 if ((err_mask &
                      (AC_ERR_DEV|AC_ERR_MEDIA|AC_ERR_INVALID)) == AC_ERR_DEV)
-                        return 3;
+                        return ATA_ECAT_UNK_DEV;
         }
 
         return 0;
@@ -1472,13 +1483,13 @@ static int ata_eh_categorize_error(int is_io, unsigned int err_mask)
 
 struct speed_down_verdict_arg {
         u64 since;
-        int nr_errors[4];
+        int nr_errors[ATA_ECAT_NR];
 };
 
 static int speed_down_verdict_cb(struct ata_ering_entry *ent, void *void_arg)
 {
         struct speed_down_verdict_arg *arg = void_arg;
-        int cat = ata_eh_categorize_error(ent->is_io, ent->err_mask);
+        int cat = ata_eh_categorize_error(ent->eflags, ent->err_mask);
 
         if (ent->timestamp < arg->since)
                 return -1;
@@ -1495,22 +1506,33 @@ static int speed_down_verdict_cb(struct ata_ering_entry *ent, void *void_arg)
  *      whether NCQ needs to be turned off, transfer speed should be
  *      stepped down, or falling back to PIO is necessary.
  *
- *      Cat-1 is ATA_BUS error for any command.
+ *      ECAT_ATA_BUS    : ATA_BUS error for any command
+ *
+ *      ECAT_TOUT_HSM   : TIMEOUT for any command or HSM violation for
+ *                        IO commands
+ *
+ *      ECAT_UNK_DEV    : Unknown DEV error for IO commands
+ *
+ *      Verdicts are
  *
- *      Cat-2 is TIMEOUT for any command or HSM violation for known
- *      supported commands.
+ *      NCQ_OFF         : Turn off NCQ.
  *
- *      Cat-3 is is unclassified DEV error for known supported
- *      command.
+ *      SPEED_DOWN      : Speed down transfer speed but don't fall back
+ *                        to PIO.
  *
- *      NCQ needs to be turned off if there have been more than 3
- *      Cat-2 + Cat-3 errors during last 10 minutes.
+ *      FALLBACK_TO_PIO : Fall back to PIO.
  *
- *      Speed down is necessary if there have been more than 3 Cat-1 +
- *      Cat-2 errors or 10 Cat-3 errors during last 10 minutes.
+ *      Even if multiple verdicts are returned, only one action is
+ *      taken per error.  ering is cleared after an action is taken.
  *
- *      Falling back to PIO mode is necessary if there have been more
- *      than 10 Cat-1 + Cat-2 + Cat-3 errors during last 5 minutes.
+ *      1. If more than 10 ATA_BUS, TOUT_HSM or UNK_DEV errors
+ *         ocurred during last 5 mins, FALLBACK_TO_PIO
+ *
+ *      2. If more than 3 TOUT_HSM or UNK_DEV errors occurred
+ *         during last 10 mins, NCQ_OFF.
+ *
+ *      3. If more than 3 ATA_BUS or TOUT_HSM errors, or more than 10
+ *         UNK_DEV errors occurred during last 10 mins, SPEED_DOWN.
  *
  *      LOCKING:
  *      Inherited from caller.
@@ -1525,23 +1547,29 @@ static unsigned int ata_eh_speed_down_verdict(struct ata_device *dev)
         struct speed_down_verdict_arg arg;
         unsigned int verdict = 0;
 
-        /* scan past 10 mins of error history */
+        /* scan past 5 mins of error history */
         memset(&arg, 0, sizeof(arg));
-        arg.since = j64 - min(j64, j10mins);
+        arg.since = j64 - min(j64, j5mins);
         ata_ering_map(&dev->ering, speed_down_verdict_cb, &arg);
 
-        if (arg.nr_errors[2] + arg.nr_errors[3] > 3)
-                verdict |= ATA_EH_SPDN_NCQ_OFF;
-        if (arg.nr_errors[1] + arg.nr_errors[2] > 3 || arg.nr_errors[3] > 10)
-                verdict |= ATA_EH_SPDN_SPEED_DOWN;
+        if (arg.nr_errors[ATA_ECAT_ATA_BUS] +
+            arg.nr_errors[ATA_ECAT_TOUT_HSM] +
+            arg.nr_errors[ATA_ECAT_UNK_DEV] > 10)
+                verdict |= ATA_EH_SPDN_FALLBACK_TO_PIO;
 
-        /* scan past 3 mins of error history */
+        /* scan past 10 mins of error history */
         memset(&arg, 0, sizeof(arg));
-        arg.since = j64 - min(j64, j5mins);
+        arg.since = j64 - min(j64, j10mins);
         ata_ering_map(&dev->ering, speed_down_verdict_cb, &arg);
 
-        if (arg.nr_errors[1] + arg.nr_errors[2] + arg.nr_errors[3] > 10)
-                verdict |= ATA_EH_SPDN_FALLBACK_TO_PIO;
+        if (arg.nr_errors[ATA_ECAT_TOUT_HSM] +
+            arg.nr_errors[ATA_ECAT_UNK_DEV] > 3)
+                verdict |= ATA_EH_SPDN_NCQ_OFF;
+
+        if (arg.nr_errors[ATA_ECAT_ATA_BUS] +
+            arg.nr_errors[ATA_ECAT_TOUT_HSM] > 3 ||
+            arg.nr_errors[ATA_ECAT_UNK_DEV] > 10)
+                verdict |= ATA_EH_SPDN_SPEED_DOWN;
 
         return verdict;
 }
@@ -1549,7 +1577,7 @@ static unsigned int ata_eh_speed_down_verdict(struct ata_device *dev)
 /**
  *      ata_eh_speed_down - record error and speed down if necessary
  *      @dev: Failed device
- *      @is_io: Did the device fail during normal IO?
+ *      @eflags: mask of ATA_EFLAG_* flags
  *      @err_mask: err_mask of the error
  *
  *      Record error and examine error history to determine whether
@@ -1563,18 +1591,19 @@ static unsigned int ata_eh_speed_down_verdict(struct ata_device *dev)
  *      RETURNS:
  *      Determined recovery action.
  */
-static unsigned int ata_eh_speed_down(struct ata_device *dev, int is_io,
-                                      unsigned int err_mask)
+static unsigned int ata_eh_speed_down(struct ata_device *dev,
+                                unsigned int eflags, unsigned int err_mask)
 {
+        struct ata_link *link = dev->link;
         unsigned int verdict;
         unsigned int action = 0;
 
         /* don't bother if Cat-0 error */
-        if (ata_eh_categorize_error(is_io, err_mask) == 0)
+        if (ata_eh_categorize_error(eflags, err_mask) == 0)
                 return 0;
 
         /* record error and determine whether speed down is necessary */
-        ata_ering_record(&dev->ering, is_io, err_mask);
+        ata_ering_record(&dev->ering, eflags, err_mask);
         verdict = ata_eh_speed_down_verdict(dev);
 
         /* turn off NCQ? */
@@ -1590,7 +1619,7 @@ static unsigned int ata_eh_speed_down(struct ata_device *dev, int is_io,
         /* speed down? */
         if (verdict & ATA_EH_SPDN_SPEED_DOWN) {
                 /* speed down SATA link speed if possible */
-                if (sata_down_spd_limit(dev->link) == 0) {
+                if (sata_down_spd_limit(link) == 0) {
                         action |= ATA_EH_HARDRESET;
                         goto done;
                 }
@@ -1621,7 +1650,7 @@ static unsigned int ata_eh_speed_down(struct ata_device *dev, int is_io,
          * SATA.  Consider it only for PATA.
          */
         if ((verdict & ATA_EH_SPDN_FALLBACK_TO_PIO) && (dev->spdn_cnt >= 2) &&
-            (dev->link->ap->cbl != ATA_CBL_SATA) &&
+            (link->ap->cbl != ATA_CBL_SATA) &&
             (dev->xfer_shift != ATA_SHIFT_PIO)) {
                 if (ata_down_xfermask_limit(dev, ATA_DNXFER_FORCE_PIO) == 0) {
                         dev->spdn_cnt = 0;
@@ -1653,8 +1682,8 @@ static void ata_eh_link_autopsy(struct ata_link *link)
         struct ata_port *ap = link->ap;
         struct ata_eh_context *ehc = &link->eh_context;
         struct ata_device *dev;
-        unsigned int all_err_mask = 0;
-        int tag, is_io = 0;
+        unsigned int all_err_mask = 0, eflags = 0;
+        int tag;
         u32 serror;
         int rc;
 
@@ -1713,15 +1742,15 @@ static void ata_eh_link_autopsy(struct ata_link *link)
                 ehc->i.dev = qc->dev;
                 all_err_mask |= qc->err_mask;
                 if (qc->flags & ATA_QCFLAG_IO)
-                        is_io = 1;
+                        eflags |= ATA_EFLAG_IS_IO;
         }
 
         /* enforce default EH actions */
         if (ap->pflags & ATA_PFLAG_FROZEN ||
             all_err_mask & (AC_ERR_HSM | AC_ERR_TIMEOUT))
                 ehc->i.action |= ATA_EH_SOFTRESET;
-        else if ((is_io && all_err_mask) ||
-                 (!is_io && (all_err_mask & ~AC_ERR_DEV)))
+        else if (((eflags & ATA_EFLAG_IS_IO) && all_err_mask) ||
+                 (!(eflags & ATA_EFLAG_IS_IO) && (all_err_mask & ~AC_ERR_DEV)))
                 ehc->i.action |= ATA_EH_REVALIDATE;
 
         /* If we have offending qcs and the associated failed device,
@@ -1744,7 +1773,7 @@ static void ata_eh_link_autopsy(struct ata_link *link)
             dev = link->device;
 
         if (dev)
-                ehc->i.action |= ata_eh_speed_down(dev, is_io, all_err_mask);
+                ehc->i.action |= ata_eh_speed_down(dev, eflags, all_err_mask);
 
         DPRINTK("EXIT\n");
 }
diff --git a/include/linux/libata.h b/include/linux/libata.h
index ca347b018649..74f1255e2524 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -482,7 +482,7 @@ struct ata_port_stats {
 };
 
 struct ata_ering_entry {
-        int                     is_io;
+        unsigned int            eflags;
         unsigned int            err_mask;
         u64                     timestamp;
 };