[PATCH] xfs: restore bi_bdev in xfs_zone_gc_write_chunk

xfs_zone_gc_write_chunk relies on bi_bdev to still be valid, which is not
true when XFS is used on top of a stacked block device.  This can lead to
misdirected GC writes, writing of plain text when using dm-crypt, or
miscalculated I/O limits in xfs_zone_gc_split_write.

Fix this by reassigning bi_bdev.

Fixes: 080d01c41d44 ("xfs: implement zoned garbage collection")
Signed-off-by: Christoph Hellwig <[email protected]>
---
 fs/xfs/xfs_zone_gc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/xfs/xfs_zone_gc.c b/fs/xfs/xfs_zone_gc.c
index 7ab8f2218c6a..5cc5ad1e3483 100644
--- a/fs/xfs/xfs_zone_gc.c
+++ b/fs/xfs/xfs_zone_gc.c
@@ -869,6 +869,11 @@ xfs_zone_gc_write_chunk(
 	WRITE_ONCE(chunk->state, XFS_GC_BIO_NEW);
 	list_move_tail(&chunk->entry, &data->writing);
 
+	/*
+	 * If we run on top of stacked block device, the read I/O might have
+	 * reset bi_bdev, restore it to the one we want.
+	 */
+	bio_set_dev(&chunk->bio, mp->m_rtdev_targp->bt_bdev);
 	bio_reuse(&chunk->bio, REQ_OP_WRITE);
 	while ((split_chunk = xfs_zone_gc_split_write(data, chunk)))
 		xfs_zone_gc_submit_write(data, split_chunk);
-- 
2.53.0