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BUG: KCSAN: data-race in ondemand_readahead / ondemand_readahead

write to 0xffff88811a4d8d84 of 4 bytes by task 8761 on cpu 0:
 ondemand_readahead+0x350/0x670
 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_splice_read+0x337/0x8f0 mm/filemap.c:2872
 ext4_file_splice_read+0x95/0xb0 fs/ext4/file.c:158
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x268/0x660 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88811a4d8d84 of 4 bytes by task 8767 on cpu 1:
 ondemand_readahead+0x158/0x670 mm/readahead.c:578
 page_cache_sync_ra+0x27e/0x2a0 mm/readahead.c:693
 page_cache_sync_readahead include/linux/pagemap.h:1300 [inline]
 filemap_get_pages+0x251/0xf90 mm/filemap.c:2498
 filemap_splice_read+0x337/0x8f0 mm/filemap.c:2872
 ext4_file_splice_read+0x95/0xb0 fs/ext4/file.c:158
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x268/0x660 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000001 -> 0x00000006

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8767 Comm: syz-executor.3 Not tainted 6.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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