Re: [syzbot] Re: [syzbot] [jfs?] INFO: task hung in txBegin

[syzbot <syzbot+eda89a33c5856f66f823@syzkaller.appspotmail.com>]

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Subject: Re: [syzbot] [jfs?] INFO: task hung in txBegin
Author: lizhi.xu@windriver.com

#syz test: upstream 50736169ecc8

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 92a5b8283528..965bd3f109cc 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2078,6 +2078,7 @@ static long wb_writeback(struct bdi_writeback *wb,
 	bool queued = false;
 
 	blk_start_plug(&plug);
+	down_write(&work->sb->s_umount);
 	for (;;) {
 		/*
 		 * Stop writeback when nr_pages has been consumed
@@ -2162,6 +2163,7 @@ static long wb_writeback(struct bdi_writeback *wb,
 		/* This function drops i_lock... */
 		inode_sleep_on_writeback(inode);
 	}
+	up_write(&work->sb->s_umount);
 	blk_finish_plug(&plug);
 
 	return nr_pages - work->nr_pages;