syzbot

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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

read-write to 0xffff888108192470 of 8 bytes by task 3287 on cpu 1:
 instrument_read_write include/linux/instrumented.h:56 [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:893 [inline]
 __xa_set_mark+0xd2/0x1a0 lib/xarray.c:2082
 __folio_mark_dirty+0x3b7/0x4b0 mm/page-writeback.c:2685
 mark_buffer_dirty+0x120/0x1f0 fs/buffer.c:1110
 block_commit_write fs/buffer.c:2115 [inline]
 block_page_mkwrite+0x261/0x300 fs/buffer.c:2540
 ext4_page_mkwrite+0x835/0xad0 fs/ext4/inode.c:6774
 do_page_mkwrite mm/memory.c:3668 [inline]
 wp_page_shared mm/memory.c:4069 [inline]
 do_wp_page+0xc65/0x2040 mm/memory.c:4288
 handle_pte_fault mm/memory.c:6427 [inline]
 __handle_mm_fault mm/memory.c:6549 [inline]
 handle_mm_fault+0x8b9/0x2e70 mm/memory.c:6718
 do_user_addr_fault+0x62f/0x1050 arch/x86/mm/fault.c:1334
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffff888108192470 of 8 bytes by task 6181 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2070 [inline]
 filemap_get_folios_tag+0xfa/0x430 mm/filemap.c:2338
 mpage_prepare_extent_to_map+0x328/0xc50 fs/ext4/inode.c:2655
 ext4_do_writepages+0x6fe/0x2770 fs/ext4/inode.c:2894
 ext4_writepages+0x18f/0x320 fs/ext4/inode.c:3042
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2571
 __writeback_single_inode+0x7f/0x650 fs/fs-writeback.c:1764
 writeback_sb_inodes+0x4dd/0xaa0 fs/fs-writeback.c:2056
 __writeback_inodes_wb+0x94/0x1a0 fs/fs-writeback.c:2132
 wb_writeback+0x261/0x560 fs/fs-writeback.c:2243
 wb_check_old_data_flush fs/fs-writeback.c:2347 [inline]
 wb_do_writeback fs/fs-writeback.c:2400 [inline]
 wb_workfn+0x635/0x930 fs/fs-writeback.c:2428
 process_one_work kernel/workqueue.c:3302 [inline]
 process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3385
 worker_thread+0x58a/0x780 kernel/workqueue.c:3466
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0xbc797c0000000000 -> 0xbc797c0040400000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6181 Comm: kworker/u8:19 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: writeback wb_workfn (flush-8:0)
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