[PATCH v9 1/6] block: add a sanity check for non-write flush/fua bios

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

From: Christoph Hellwig <hch@infradead.org>

Check that the PREFUSH and FUA flags are only set on write bios,
given that the flush state machine expects that.

[Damien] The check is also extended to REQ_OP_ZONE_APPEND operations as
these are data write operations used by btrfs and zonefs and may also
have the REQ_FUA bit set.

Reported-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
---
 block/blk-core.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 9321767470dc..c644aac498ef 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -744,12 +744,16 @@ void submit_bio_noacct(struct bio *bio)
 	 * Filter flush bio's early so that bio based drivers without flush
 	 * support don't have to worry about them.
 	 */
-	if (op_is_flush(bio->bi_opf) &&
-	    !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
-		bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA);
-		if (!bio_sectors(bio)) {
-			status = BLK_STS_OK;
+	if (op_is_flush(bio->bi_opf)) {
+		if (WARN_ON_ONCE(bio_op(bio) != REQ_OP_WRITE &&
+				 bio_op(bio) != REQ_OP_ZONE_APPEND))
 			goto end_io;
+		if (!test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
+			bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA);
+			if (!bio_sectors(bio)) {
+				status = BLK_STS_OK;
+				goto end_io;
+			}
 		}
 	}
 
-- 
2.39.0