[PATCH] libata: fix bug with non-ncq devices

[Jens Axboe]

The recent commit 201f1b98822078c808b5e2d379a6ddbfc0a06ee1 to enable
support for block layer tagging in libata was broken for non-NCQ
devices. The block layer initializes the tag field to -1 to detect
invalid uses of a tag, and if the libata devices does NOT support
NCQ, we just used that field to index the internal command list.
So we need to check for -1 first and only use the tag field if
it's valid.

Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
---
 drivers/ata/libata-scsi.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index d5b9b72..4b95c43 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -708,7 +708,11 @@ static struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev,
 {
 	struct ata_queued_cmd *qc;
 
-	qc = ata_qc_new_init(dev, cmd->request->tag);
+	if (cmd->request->tag != -1)
+		qc = ata_qc_new_init(dev, cmd->request->tag);
+	else
+		qc = ata_qc_new_init(dev, 0);
+
 	if (qc) {
 		qc->scsicmd = cmd;
 		qc->scsidone = done;
-- 
1.6.0.2.588.g3102


-- 
Jens Axboe

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