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>

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 7ef7c4f216fa58567e161c82118155411d070074..c035b3d041ee1572492d7a17f56323bde0fccacd 100644 (file)
--- 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);