[PATCH v3 2/4] block: Ignore REQ_NOWAIT for zone reset and zone finish operations

[Damien Le Moal <dlemoal@kernel.org>]

There are currently any issuer of REQ_OP_ZONE_RESET and
REQ_OP_ZONE_FINISH operations that set REQ_NOWAIT. However, as we cannot
handle this flag correctly due to the potential request allocation
failure that may happen in blk_mq_submit_bio() after blk_zone_plug_bio()
has handled the zone write plug write pointer updates for the targeted
zones, modify blk_zone_wplug_handle_reset_or_finish() to warn if this
flag is set and ignore it.

Fixes: dd291d77cc90 ("block: Introduce zone write plugging")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-zoned.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 7982b9494d63..ee9c67121c6c 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -707,6 +707,15 @@ static bool blk_zone_wplug_handle_reset_or_finish(struct bio *bio,
 		return true;
 	}
 
+	/*
+	 * No-wait reset or finish BIOs do not make much sense as the callers
+	 * issue these as blocking operations in most cases. To avoid issues
+	 * the BIO execution potentially failing with BLK_STS_AGAIN, warn about
+	 * REQ_NOWAIT being set and ignore that flag.
+	 */
+	if (WARN_ON_ONCE(bio->bi_opf & REQ_NOWAIT))
+		bio->bi_opf &= ~REQ_NOWAIT;
+
 	/*
 	 * If we have a zone write plug, set its write pointer offset to 0
 	 * (reset case) or to the zone size (finish case). This will abort all
-- 
2.47.1