From f4bd34b139a3fa2808c4205f12714c65e1548c6c Mon Sep 17 00:00:00 2001
From: Zheng Bin <zhengbin13@huawei.com>
Date: Thu, 18 Jun 2020 12:21:37 +0800
Subject: [PATCH] loop: replace kill_bdev with invalidate_bdev
Git-commit: f4bd34b139a3fa2808c4205f12714c65e1548c6c
Patch-mainline: v5.8-rc2
References: bsc#1173820

When a filesystem is mounted on a loop device and on a loop ioctl
LOOP_SET_STATUS64, because of kill_bdev, buffer_head mappings are getting
destroyed.
kill_bdev
  truncate_inode_pages
    truncate_inode_pages_range
      do_invalidatepage
        block_invalidatepage
          discard_buffer  -->clear BH_Mapped flag

sb_bread
  __bread_gfp
  bh = __getblk_gfp
  -->discard_buffer clear BH_Mapped flag
  __bread_slow
    submit_bh
      submit_bh_wbc
        BUG_ON(!buffer_mapped(bh))  --> hit this BUG_ON

Fixes: 5db470e229e2 ("loop: drop caches if offset or block_size are changed")
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Jan Kara <jack@suse.cz>

---
 drivers/block/loop.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1160,7 +1160,7 @@ loop_set_status(struct loop_device *lo,
 	if (lo->lo_offset != info->lo_offset ||
 	    lo->lo_sizelimit != info->lo_sizelimit) {
 		sync_blockdev(lo->lo_device);
-		kill_bdev(lo->lo_device);
+		invalidate_bdev(lo->lo_device);
 	}
 
 	/* I/O need to be drained during transfer transition */
@@ -1207,7 +1207,7 @@ loop_set_status(struct loop_device *lo,
 
 	if (lo->lo_offset != info->lo_offset ||
 	    lo->lo_sizelimit != info->lo_sizelimit) {
-		/* kill_bdev should have truncated all the pages */
+		/* invalidate_bdev should have truncated all the pages */
 		if (lo->lo_device->bd_inode->i_mapping->nrpages) {
 			err = -EAGAIN;
 			pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
@@ -1407,13 +1407,13 @@ static int loop_set_block_size(struct
 
 	if (lo->lo_queue->limits.logical_block_size != arg) {
 		sync_blockdev(lo->lo_device);
-		kill_bdev(lo->lo_device);
+		invalidate_bdev(lo->lo_device);
 	}
 
 	blk_mq_freeze_queue(lo->lo_queue);
 
-	/* kill_bdev should have truncated all the pages */
+	/* invalidate_bdev should have truncated all the pages */
 	if (lo->lo_queue->limits.logical_block_size != arg &&
 			lo->lo_device->bd_inode->i_mapping->nrpages) {
 		err = -EAGAIN;
 		pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",