[PATCH] libata: clear ap->active_tag atomically w.r.t. command completion

ap->active_tag was cleared in ata_qc_free().  This left ap->active_tag
dangling after ata_qc_complete().  Spurious interrupts inbetween could
incorrectly access the qc.  Clear active_tag in ata_qc_complete().
This change is necessary for later EH changes.

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

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 1669dae53ce3..86cd0e0895d0 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -4083,8 +4083,6 @@ void ata_qc_free(struct ata_queued_cmd *qc)
         qc->flags = 0;
         tag = qc->tag;
         if (likely(ata_tag_valid(tag))) {
-                if (tag == ap->active_tag)
-                        ap->active_tag = ATA_TAG_POISON;
                 qc->tag = ATA_TAG_POISON;
                 clear_bit(tag, &ap->qactive);
         }
@@ -4098,6 +4096,9 @@ void __ata_qc_complete(struct ata_queued_cmd *qc)
         if (likely(qc->flags & ATA_QCFLAG_DMAMAP))
                 ata_sg_clean(qc);
 
+        /* command should be marked inactive atomically with qc completion */
+        qc->ap->active_tag = ATA_TAG_POISON;
+
         /* atapi: mark qc as inactive to prevent the interrupt handler
          * from completing the command twice later, before the error handler
          * is called. (when rc != 0 and atapi request sense is needed)