libata: be less of a drama queen on empty data commands

ata_qc_issue() BUG_ON()s on data commands w/o data, which may be
submitted via SG_IO.  Be less of a drama queen and just trigger
WARN_ON_ONCE() and fail the command with AC_ERR_SYSTEM.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Stefan Hübner <stefan.huebner@stud.tu-ilmenau.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 7ef7c4f216f..c035b3d041e 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5111,15 +5111,18 @@ void ata_qc_issue(struct ata_queued_cmd *qc)
         qc->flags |= ATA_QCFLAG_ACTIVE;
         ap->qc_active |= 1 << qc->tag;
 
-        /* We guarantee to LLDs that they will have at least one
+        /*
+         * We guarantee to LLDs that they will have at least one
          * non-zero sg if the command is a data command.
          */
-        BUG_ON(ata_is_data(prot) && (!qc->sg || !qc->n_elem || !qc->nbytes));
+        if (WARN_ON_ONCE(ata_is_data(prot) &&
+                         (!qc->sg || !qc->n_elem || !qc->nbytes)))
+                goto sys_err;
 
         if (ata_is_dma(prot) || (ata_is_pio(prot) &&
                                  (ap->flags & ATA_FLAG_PIO_DMA)))
                 if (ata_sg_setup(qc))
-                        goto sg_err;
+                        goto sys_err;
 
         /* if device is sleeping, schedule reset and abort the link */
         if (unlikely(qc->dev->flags & ATA_DFLAG_SLEEPING)) {
@@ -5136,7 +5139,7 @@ void ata_qc_issue(struct ata_queued_cmd *qc)
                 goto err;
         return;
 
-sg_err:
+sys_err:
         qc->err_mask |= AC_ERR_SYSTEM;
 err:
         ata_qc_complete(qc);