block: fix bio_split_rw_at to take zone_write_granularity into account

Otherwise it can create unaligned writes on zoned devices.

Fixes: a805a4f ("block: introduce zone_write_granularity limit")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20241104062647.91160-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

block/blk-merge.c

@@ -292,6 +292,14 @@ static bool bvec_split_segs(const struct queue_limits *lim,
 	return len > 0 || bv->bv_len > max_len;
 }
 
+static unsigned int bio_split_alignment(struct bio *bio,
+		const struct queue_limits *lim)
+{
+	if (op_is_write(bio_op(bio)) && lim->zone_write_granularity)
+		return lim->zone_write_granularity;
+	return lim->logical_block_size;
+}
+
 /**
  * bio_split_rw_at - check if and where to split a read/write bio
  * @bio:  [in] bio to be split
@@ -354,7 +362,7 @@ int bio_split_rw_at(struct bio *bio, const struct queue_limits *lim,
 	 * split size so that each bio is properly block size aligned, even if
 	 * we do not use the full hardware limits.
 	 */
-	bytes = ALIGN_DOWN(bytes, lim->logical_block_size);
+	bytes = ALIGN_DOWN(bytes, bio_split_alignment(bio, lim));
 
 	/*
 	 * Bio splitting may cause subtle trouble such as hang when doing sync