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BUG: KCSAN: data-race in ondemand_readahead / ondemand_readahead

write to 0xffff88821df3f478 of 8 bytes by task 3571 on cpu 0:
 ondemand_readahead+0x566/0x690 mm/readahead.c:604
 page_cache_async_ra+0x94/0xa0 mm/readahead.c:715
 do_async_mmap_readahead mm/filemap.c:3181 [inline]
 filemap_fault+0x3da/0xc30 mm/filemap.c:3235
 __do_fault+0xb2/0x1f0 mm/memory.c:4376
 do_shared_fault mm/memory.c:4798 [inline]
 do_fault mm/memory.c:4872 [inline]
 do_pte_missing mm/memory.c:3745 [inline]
 handle_pte_fault mm/memory.c:5144 [inline]
 __handle_mm_fault mm/memory.c:5285 [inline]
 handle_mm_fault+0xb9a/0x27b0 mm/memory.c:5450
 do_user_addr_fault arch/x86/mm/fault.c:1415 [inline]
 handle_page_fault arch/x86/mm/fault.c:1507 [inline]
 exc_page_fault+0x2f7/0x6d0 arch/x86/mm/fault.c:1563
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
 rep_movs_alternative+0x4a/0x70 arch/x86/lib/copy_user_64.S:65
 copy_user_generic arch/x86/include/asm/uaccess_64.h:112 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:133 [inline]
 copy_to_user_iter lib/iov_iter.c:25 [inline]
 iterate_iovec include/linux/iov_iter.h:51 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:247 [inline]
 iterate_and_advance include/linux/iov_iter.h:271 [inline]
 _copy_to_iter+0x2bf/0xb20 lib/iov_iter.c:186
 copy_page_to_iter+0x171/0x2b0 lib/iov_iter.c:381
 copy_folio_to_iter include/linux/uio.h:181 [inline]
 filemap_read+0x42c/0x680 mm/filemap.c:2654
 generic_file_read_iter+0x78/0x330 mm/filemap.c:2784
 ext4_file_read_iter+0x1d8/0x2a0
 do_iter_readv_writev+0x2b0/0x330
 vfs_readv+0x1e5/0x640 fs/read_write.c:932
 do_preadv fs/read_write.c:1049 [inline]
 __do_sys_preadv fs/read_write.c:1099 [inline]
 __se_sys_preadv fs/read_write.c:1094 [inline]
 __x64_sys_preadv+0x100/0x1c0 fs/read_write.c:1094
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88821df3f478 of 8 bytes by task 3575 on cpu 1:
 ondemand_readahead+0x13a/0x690 mm/readahead.c:578
 page_cache_async_ra+0x94/0xa0 mm/readahead.c:715
 filemap_readahead mm/filemap.c:2473 [inline]
 filemap_get_pages+0x397/0xf90 mm/filemap.c:2514
 filemap_read+0x214/0x680 mm/filemap.c:2594
 generic_file_read_iter+0x78/0x330 mm/filemap.c:2784
 ext4_file_read_iter+0x1d8/0x2a0
 do_iter_readv_writev+0x2b0/0x330
 vfs_readv+0x1e5/0x640 fs/read_write.c:932
 do_preadv fs/read_write.c:1049 [inline]
 __do_sys_preadv fs/read_write.c:1099 [inline]
 __se_sys_preadv fs/read_write.c:1094 [inline]
 __x64_sys_preadv+0x100/0x1c0 fs/read_write.c:1094
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000412 -> 0x0000000000000415

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3575 Comm: syz-executor.2 Not tainted 6.8.0-rc1-syzkaller-00311-g3a5879d495b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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