Merge branch 'for-3.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata

torvalds · torvalds · commit ea9339e56460 · 2014-07-23T17:39:28.000-07:00
Pull libata regression fix from Tejun Heo: "The last libata/for-3.16-fixes pull contained a regression introduced by 1871ee1 ("libata: support the ata host which implements a queue depth less than 32") which in turn was a fix for a regression introduced earlier while changing queue tag order to accomodate hard drives which perform poorly if tags are not allocated in circular order (ugh...). The regression happens only for SAS controllers making use of libata to serve ATA devices. They don't fill an ata_host field which is used by the new tag allocation function leading to NULL dereference. This patch adds a new intermediate field ata_host->n_tags which is initialized for both SAS and !SAS cases to fix the issue" * 'for-3.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata: libata: introduce ata_host->n_tags to avoid oops on SAS controllers
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
@@ -4798,9 +4798,8 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
 static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
 {
 	struct ata_queued_cmd *qc = NULL;
-	unsigned int i, tag, max_queue;
-
-	max_queue = ap->scsi_host->can_queue;
+	unsigned int max_queue = ap->host->n_tags;
+	unsigned int i, tag;
 
 	/* no command while frozen */
 	if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
@@ -6094,6 +6093,7 @@ void ata_host_init(struct ata_host *host, struct device *dev,
 {
 	spin_lock_init(&host->lock);
 	mutex_init(&host->eh_mutex);
+	host->n_tags = ATA_MAX_QUEUE - 1;
 	host->dev = dev;
 	host->ops = ops;
 }
@@ -6175,15 +6175,7 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
 {
 	int i, rc;
 
-	/*
-	 * The max queue supported by hardware must not be greater than
-	 * ATA_MAX_QUEUE.
-	 */
-	if (sht->can_queue > ATA_MAX_QUEUE) {
-		dev_err(host->dev, "BUG: the hardware max queue is too large\n");
-		WARN_ON(1);
-		return -EINVAL;
-	}
+	host->n_tags = clamp(sht->can_queue, 1, ATA_MAX_QUEUE - 1);
 
 	/* host must have been started */
 	if (!(host->flags & ATA_HOST_STARTED)) {
diff --git a/include/linux/libata.h b/include/linux/libata.h
@@ -593,6 +593,7 @@ struct ata_host {
 	struct device 		*dev;
 	void __iomem * const	*iomap;
 	unsigned int		n_ports;
+	unsigned int		n_tags;			/* nr of NCQ tags */
 	void			*private_data;
 	struct ata_port_operations *ops;
 	unsigned long		flags;
