------------[ cut here ]------------
!buffer_uptodate(bh)
WARNING: fs/buffer.c:1093 at mark_buffer_dirty+0x299/0x410 fs/buffer.c:1093, CPU#0: syz.0.0/5336
Modules linked in:
CPU: 0 UID: 0 PID: 5336 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:mark_buffer_dirty+0x299/0x410 fs/buffer.c:1093
Code: 4c 89 f7 e8 c9 11 d9 ff 49 8b 3e be 40 00 00 00 5b 41 5c 41 5e 41 5f 5d e9 d4 5e fb ff e8 8f f3 69 ff eb 8c e8 88 f3 69 ff 90 <0f> 0b 90 e9 a5 fd ff ff e8 7a f3 69 ff 90 0f 0b 90 e9 cf fd ff ff
RSP: 0018:ffffc9000db3e688 EFLAGS: 00010293
RAX: ffffffff825c7e88 RBX: ffff888043e82700 RCX: ffff888012a5a540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: 0000000000000201 R08: ffff888043e82707 R09: 1ffff110087d04e0
R10: dffffc0000000000 R11: ffffed10087d04e1 R12: 0000000000000013
R13: ffff888043e82700 R14: ffff888043e85a80 R15: dffffc0000000000
FS:  00007fc8618fe6c0(0000) GS:ffff88808c815000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc854935000 CR3: 000000001f045000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 bfs_move_block fs/bfs/file.c:44 [inline]
 bfs_move_blocks fs/bfs/file.c:57 [inline]
 bfs_get_block+0x5c6/0xb50 fs/bfs/file.c:126
 __block_write_begin_int+0x6c2/0x1900 fs/buffer.c:2123
 block_write_begin+0x8d/0x120 fs/buffer.c:2234
 bfs_write_begin+0x35/0xd0 fs/bfs/file.c:180
 generic_perform_write+0x2d5/0x8f0 mm/filemap.c:4358
 generic_file_write_iter+0xae/0x330 mm/filemap.c:4501
 __kernel_write_iter+0x44a/0x8f0 fs/read_write.c:621
 __kernel_write+0x106/0x170 fs/read_write.c:641
 __dump_emit fs/coredump.c:1220 [inline]
 dump_emit+0x920/0xb00 fs/coredump.c:1258
 elf_core_dump+0x2ff4/0x3a90 fs/binfmt_elf.c:2088
 coredump_write+0x1290/0x1960 fs/coredump.c:1052
 do_coredump fs/coredump.c:1131 [inline]
 vfs_coredump+0x36ff/0x44b0 fs/coredump.c:1200
 get_signal+0x1094/0x12c0 kernel/signal.c:3023
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:101 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x2ba/0x8f0 kernel/entry/common.c:165
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x7fc86099ce61
Code: 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 48 3d 01 f0 ff ff 73 01 <c3> 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
RSP: 002b:00000000fffffeb0 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007fc860c16090 RCX: 00007fc86099ce59
RDX: 0000000000000000 RSI: 00000000fffffeb0 RDI: 0000000002000400
RBP: 00007fc860a32e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fc860c16128 R14: 00007fc860c16090 R15: 00007ffc524b1f58
 </TASK>