[PATCH] libata-eh: implement dev->ering

This patch implements ata_ering and uses it to define dev->ering.

ata_ering is a ring buffer which records libata errors - whether a
command was for normar IO request, err_mask and timestamp.  Errors are
recorded per-device in dev->ering.  This will be used by EH to
determine recovery actions.

Signed-off-by: Tejun Heo <htejun@gmail.com>

2 files changed, 62 insertions, 0 deletions

diff --git a/drivers/scsi/libata-eh.c b/drivers/scsi/libata-eh.c
index 0803231f6577..71ad18b7cff6 100644
--- a/drivers/scsi/libata-eh.c
+++ b/drivers/scsi/libata-eh.c
@@ -46,6 +46,51 @@
 
 static void __ata_port_freeze(struct ata_port *ap);
 
+static void ata_ering_record(struct ata_ering *ering, int is_io,
+                             unsigned int err_mask)
+{
+        struct ata_ering_entry *ent;
+
+        WARN_ON(!err_mask);
+
+        ering->cursor++;
+        ering->cursor %= ATA_ERING_SIZE;
+
+        ent = &ering->ring[ering->cursor];
+        ent->is_io = is_io;
+        ent->err_mask = err_mask;
+        ent->timestamp = get_jiffies_64();
+}
+
+static struct ata_ering_entry * ata_ering_top(struct ata_ering *ering)
+{
+        struct ata_ering_entry *ent = &ering->ring[ering->cursor];
+        if (!ent->err_mask)
+                return NULL;
+        return ent;
+}
+
+static int ata_ering_map(struct ata_ering *ering,
+                         int (*map_fn)(struct ata_ering_entry *, void *),
+                         void *arg)
+{
+        int idx, rc = 0;
+        struct ata_ering_entry *ent;
+
+        idx = ering->cursor;
+        do {
+                ent = &ering->ring[idx];
+                if (!ent->err_mask)
+                        break;
+                rc = map_fn(ent, arg);
+                if (rc)
+                        break;
+                idx = (idx - 1 + ATA_ERING_SIZE) % ATA_ERING_SIZE;
+        } while (idx != ering->cursor);
+
+        return rc;
+}
+
 /**
  *      ata_scsi_timed_out - SCSI layer time out callback
  *      @cmd: timed out SCSI command
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6fe5ed8eabf5..f5cea13599c3 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -226,6 +226,9 @@ enum {
         ATA_PORT_PRIMARY        = (1 << 0),
         ATA_PORT_SECONDARY      = (1 << 1),
 
+        /* ering size */
+        ATA_ERING_SIZE          = 32,
+
         /* reset / recovery action types */
         ATA_EH_REVALIDATE       = (1 << 0),
         ATA_EH_SOFTRESET        = (1 << 1),
@@ -375,6 +378,17 @@ struct ata_host_stats {
         unsigned long           rw_reqbuf;
 };
 
+struct ata_ering_entry {
+        int                     is_io;
+        unsigned int            err_mask;
+        u64                     timestamp;
+};
+
+struct ata_ering {
+        int                     cursor;
+        struct ata_ering_entry  ring[ATA_ERING_SIZE];
+};
+
 struct ata_device {
         struct ata_port         *ap;
         u64                     n_sectors;      /* size of device, if ATA */
@@ -401,6 +415,9 @@ struct ata_device {
         u16                     cylinders;      /* Number of cylinders */
         u16                     heads;          /* Number of heads */
         u16                     sectors;        /* Number of sectors per track */
+
+        /* error history */
+        struct ata_ering        ering;
 };
 
 struct ata_port {