This is disallowed.

This check will now be relevant since the device mapper personalities
will start to support atomic writes, and they use this function.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 block/bio.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index 4e1a27d312c9..f0c416e5931d 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1610,6 +1610,10 @@ EXPORT_SYMBOL(bio_split);
  */
 void bio_trim(struct bio *bio, sector_t offset, sector_t size)
 {
+	/* We should never trim an atomic write */
+	if (WARN_ON_ONCE(bio->bi_opf & REQ_ATOMIC && size))
+		return;
+
 	if (WARN_ON_ONCE(offset > BIO_MAX_SECTORS || size > BIO_MAX_SECTORS ||
 			 offset + size > bio_sectors(bio)))
 		return;
-- 
2.31.1