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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

read-write to 0xffff88811d6d1220 of 8 bytes by task 6896 on cpu 0:
 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:95 [inline]
 xas_set_mark lib/xarray.c:892 [inline]
 __xa_set_mark+0xdb/0x1b0 lib/xarray.c:1943
 __folio_mark_dirty+0x3b5/0x4e0 mm/page-writeback.c:2798
 mark_buffer_dirty+0x134/0x230 fs/buffer.c:1196
 __block_write_begin_int+0x84d/0xfa0 fs/buffer.c:2127
 block_page_mkwrite+0x1bd/0x3f0 fs/buffer.c:2629
 ext4_page_mkwrite+0x73d/0xb70 fs/ext4/inode.c:6181
 do_page_mkwrite mm/memory.c:3257 [inline]
 do_shared_fault mm/memory.c:5486 [inline]
 do_fault mm/memory.c:5548 [inline]
 do_pte_missing mm/memory.c:4060 [inline]
 handle_pte_fault mm/memory.c:5907 [inline]
 __handle_mm_fault mm/memory.c:6050 [inline]
 handle_mm_fault+0x12f7/0x2ac0 mm/memory.c:6219
 do_user_addr_fault arch/x86/mm/fault.c:1337 [inline]
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x3b9/0x650 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffff88811d6d1220 of 8 bytes by task 12 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1733 [inline]
 xas_find_marked+0x217/0x650 lib/xarray.c:1377
 find_get_entry+0x54/0x390 mm/filemap.c:2017
 filemap_get_folios_tag+0x136/0x210 mm/filemap.c:2284
 mpage_prepare_extent_to_map+0x329/0xb80 fs/ext4/inode.c:2448
 ext4_do_writepages+0xa20/0x2130 fs/ext4/inode.c:2733
 ext4_writepages+0x159/0x2e0 fs/ext4/inode.c:2824
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2687
 __writeback_single_inode+0x89/0x850 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x461/0xa30 fs/fs-writeback.c:1976
 __writeback_inodes_wb+0x9a/0x1a0 fs/fs-writeback.c:2047
 wb_writeback+0x274/0x640 fs/fs-writeback.c:2158
 wb_check_start_all fs/fs-writeback.c:2284 [inline]
 wb_do_writeback fs/fs-writeback.c:2310 [inline]
 wb_workfn+0x4ea/0x940 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4db/0xa20 kernel/workqueue.c:3319
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3400
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x0000fffc00000000 -> 0x0003fffc00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted 6.14.0-rc6-syzkaller-00003-g4d872d51bc9d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: writeback wb_workfn (flush-8:0)
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