[PATCH 1/6] zloop: fix write pointer calculation in zloop_forget_cache

[Christoph Hellwig <hch@lst.de>]

The write pointer is absolute and in sector units, so we need to
convert it to a relative byte address first.

Fixes: c505448748f7 ("zloop: forget write cache on force removal")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/zloop.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zloop.c b/drivers/block/zloop.c
index 8baf642037fd..672948d3653e 100644
--- a/drivers/block/zloop.c
+++ b/drivers/block/zloop.c
@@ -1401,8 +1401,17 @@ static void zloop_forget_cache(struct zloop_device *zlo)
 				zlo->disk->part0, ret);
 			continue;
 		}
-		if (old_wp < zone->wp)
-			zloop_truncate(file, old_wp);
+
+		if (old_wp > zone->wp)
+			continue;
+		/*
+		 * This should not happen, if we recored a full zone, it can't
+		 * be active.
+		 */
+		if (WARN_ON_ONCE(old_wp == ULLONG_MAX))
+			continue;
+
+		zloop_truncate(file, (old_wp - zone->start) << SECTOR_SHIFT);
 	}
 }
 
-- 
2.53.0