libata: clear dev->ering in smarter way

dev->ering used to be cleared together with the rest of ata_device in
ata_dev_init() which is called whenever a probing event occurs.
dev->ering is about to be used to track probing failures so it needs
to remain persistent over multiple porbing events.  This patch
achieves this by doing the following.

* Instead of CLEAR_OFFSET, define CLEAR_BEGIN and CLEAR_END and only
  clear between BEGIN and END.  ering is moved after END.  The split
  of persistent area is to allow hotter items remain at the head.

* ering is explicitly cleared on ata_dev_disable() and when device
  attach succeeds.  So, ering is persistent throug a device's life
  time (unless explicitly cleared of course) and also through periods
  inbetween disablement of an attached device and successful detection
  of the next one.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index d006e5c4768c..564c03c4ebb3 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5404,8 +5404,8 @@ void ata_dev_init(struct ata_device *dev)
         dev->horkage = 0;
         spin_unlock_irqrestore(ap->lock, flags);
 
-        memset((void *)dev + ATA_DEVICE_CLEAR_OFFSET, 0,
-               sizeof(*dev) - ATA_DEVICE_CLEAR_OFFSET);
+        memset((void *)dev + ATA_DEVICE_CLEAR_BEGIN, 0,
+               ATA_DEVICE_CLEAR_END - ATA_DEVICE_CLEAR_BEGIN);
         dev->pio_mask = UINT_MAX;
         dev->mwdma_mask = UINT_MAX;
         dev->udma_mask = UINT_MAX;