linux-kernel - [RFC 3/3] ata: sata_mv, avoid trigerrable BUG

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Date:   Fri, 14 Jun 2019 09:11:40 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     axboe@...nel.dk
Cc:     linux-kernel@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>,
        linux-ide@...r.kernel.org
Subject: [RFC 3/3] ata: sata_mv, avoid trigerrable BUG_ON

There are several reports that the BUG_ON on unsupported command in
mv_qc_prep can be triggered under some circumstances:
https://bugzilla.suse.com/show_bug.cgi?id=1110252
https://serverfault.com/questions/888897/raid-problems-after-power-outage
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1652185
https://bugs.centos.org/view.php?id=14998

Let sata_mv handle the failure gracefully: warn about that incl. the
failed command number and return an AC_ERR_INVALID error. We can do that
now thanks to the previous patch.

Remove also the long-standing FIXME.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: linux-ide@...r.kernel.org
---
 drivers/ata/sata_mv.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index d6aac7b31c45..144fa0982168 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -2098,12 +2098,10 @@ static int mv_qc_prep(struct ata_queued_cmd *qc)
 		 * non-NCQ mode are: [RW] STREAM DMA and W DMA FUA EXT, none
 		 * of which are defined/used by Linux.  If we get here, this
 		 * driver needs work.
-		 *
-		 * FIXME: modify libata to give qc_prep a return value and
-		 * return error here.
 		 */
-		BUG_ON(tf->command);
-		break;
+		ata_port_err(ap, "%s: unsupported command: %d\n", __func__,
+				tf->command);
+		return AC_ERR_INVALID;
 	}
 	mv_crqb_pack_cmd(cw++, tf->nsect, ATA_REG_NSECT, 0);
 	mv_crqb_pack_cmd(cw++, tf->hob_lbal, ATA_REG_LBAL, 0);
-- 
2.22.0