syzbot

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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

read-write to 0xffff88812d3958e8 of 8 bytes by task 18914 on cpu 1:
 instrument_read_write include/linux/instrumented.h:55 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
 ___test_and_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:99 [inline]
 node_set_mark lib/xarray.c:93 [inline]
 xas_set_mark lib/xarray.c:887 [inline]
 __xa_set_mark+0xdb/0x1b0 lib/xarray.c:1906
 __folio_mark_dirty+0x3c5/0x4e0 mm/page-writeback.c:2668
 mark_buffer_dirty+0x148/0x240 fs/buffer.c:1154
 __block_commit_write+0x10a/0x1a0 fs/buffer.c:2138
 block_write_end fs/buffer.c:2217 [inline]
 generic_write_end+0x7f/0x360 fs/buffer.c:2231
 ext4_da_write_end+0x4df/0x690 fs/ext4/inode.c:3012
 generic_perform_write+0x253/0x3d0 mm/filemap.c:3934
 ext4_buffered_write_iter+0x234/0x3e0 fs/ext4/file.c:289
 ext4_file_write_iter+0xd7/0x10e0
 __kernel_write_iter+0x15c/0x380 fs/read_write.c:517
 dump_emit_page fs/coredump.c:888 [inline]
 dump_user_range+0x25d/0x490 fs/coredump.c:915
 elf_core_dump+0x1a73/0x1b90 fs/binfmt_elf.c:2142
 do_coredump+0x1029/0x1870 fs/coredump.c:764
 get_signal+0xd65/0xff0 kernel/signal.c:2862
 arch_do_signal_or_restart+0x89/0x2a0 arch/x86/kernel/signal.c:306
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 irqentry_exit_to_user_mode+0x9/0x20 kernel/entry/common.c:310
 irqentry_exit+0x12/0x40 kernel/entry/common.c:413
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

read to 0xffff88812d3958e8 of 8 bytes by task 18393 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1705 [inline]
 xas_find_marked+0x216/0x660 lib/xarray.c:1356
 find_get_entry+0x5d/0x290 mm/filemap.c:2007
 filemap_get_folios_tag+0x136/0x230 mm/filemap.c:2305
 mpage_prepare_extent_to_map+0x321/0xb50 fs/ext4/inode.c:2415
 ext4_do_writepages+0xa5e/0x21e0 fs/ext4/inode.c:2701
 ext4_writepages+0x15e/0x2e0 fs/ext4/inode.c:2792
 do_writepages+0x1c5/0x340 mm/page-writeback.c:2551
 __writeback_single_inode+0x91/0x860 fs/fs-writeback.c:1603
 writeback_sb_inodes+0x511/0xaa0 fs/fs-writeback.c:1894
 __writeback_inodes_wb+0x9a/0x1a0 fs/fs-writeback.c:1965
 wb_writeback+0x24d/0x6c0 fs/fs-writeback.c:2070
 wb_check_start_all fs/fs-writeback.c:2192 [inline]
 wb_do_writeback fs/fs-writeback.c:2218 [inline]
 wb_workfn+0x4ea/0x8d0 fs/fs-writeback.c:2251
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2405
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2552
 kthread+0x1d7/0x210 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x00000001fe000000 -> 0x00000007fe000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18393 Comm: kworker/u4:1 Tainted: G        W          6.4.0-rc5-syzkaller-00016-ga4d7d7011219 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
Workqueue: writeback wb_workfn (flush-8:0)
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