Re: KASAN: null-ptr-deref Write in start_transaction

[syzbot]

syzbot suspects this issue was fixed by commit:

commit f30bed83426c5cb9fce6cabb3f7cc5a9d5428fcc
Author: Filipe Manana <fdmanana@xxxxxxxx>
Date:   Fri Nov 13 11:24:17 2020 +0000

    btrfs: remove unnecessary attempt to drop extent maps after adding inline extent

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13ddc30b500000
start commit:   521b619a Merge tag 'linux-kselftest-kunit-fixes-5.10-rc3' ..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=61033507391c77ff
dashboard link: https://syzkaller.appspot.com/bug?extid=6700bca07dff187809c4
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14a07ab2500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10fe69c6500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: btrfs: remove unnecessary attempt to drop extent maps after adding inline extent

For information about bisection process see: https://goo.gl/tpsmEJ#bisection