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BUG: KCSAN: data-race in next_uptodate_folio / shmem_write_end

write to 0xffff8881378d86b0 of 8 bytes by task 12403 on cpu 1:
 i_size_write include/linux/fs.h:932 [inline]
 shmem_write_end+0x9a/0x470 mm/shmem.c:2741
 generic_perform_write+0x267/0x410 mm/filemap.c:3941
 shmem_file_write_iter+0xc8/0xe0 mm/shmem.c:2893
 call_write_iter include/linux/fs.h:2085 [inline]
 iter_file_splice_write+0x5de/0x950 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x167/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x2fb/0x660 fs/splice.c:1108
 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:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/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 0xffff8881378d86b0 of 8 bytes by task 12409 on cpu 0:
 i_size_read include/linux/fs.h:910 [inline]
 next_uptodate_folio+0x5c9/0x7a0 mm/filemap.c:3420
 filemap_map_pages+0xed/0x900 mm/filemap.c:3533
 do_fault_around mm/memory.c:4696 [inline]
 do_read_fault mm/memory.c:4729 [inline]
 do_fault mm/memory.c:4868 [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+0x1063/0x27c0 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+0x2f9/0x6d0 arch/x86/mm/fault.c:1563
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
 __get_user_4+0x11/0x20 arch/x86/lib/getuser.S:75
 rds_getsockopt+0x5c/0x420 net/rds/af_rds.c:493
 do_sock_getsockopt+0x11d/0x190 net/socket.c:2373
 __sys_getsockopt+0x199/0x200 net/socket.c:2402
 __do_sys_getsockopt net/socket.c:2412 [inline]
 __se_sys_getsockopt net/socket.c:2409 [inline]
 __x64_sys_getsockopt+0x66/0x80 net/socket.c:2409
 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: 0x0000000000007b78 -> 0x0000000000007ba8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12409 Comm: syz-executor.1 Not tainted 6.8.0-rc5-syzkaller-00029-g39133352cbed #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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