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BUG: KCSAN: data-race in shmem_file_read_iter / shmem_write_end

write to 0xffff88813a6ae9f0 of 8 bytes by task 4180 on cpu 0:
 i_size_write include/linux/fs.h:932 [inline]
 shmem_write_end+0x9a/0x470 mm/shmem.c:2743
 generic_perform_write+0x267/0x410 mm/filemap.c:3938
 shmem_file_write_iter+0xc8/0xe0 mm/shmem.c:2895
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x48a/0x790 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88813a6ae9f0 of 8 bytes by task 4187 on cpu 1:
 i_size_read include/linux/fs.h:910 [inline]
 shmem_file_read_iter+0x3b0/0x550 mm/shmem.c:2779
 do_iter_read+0x4af/0x780 fs/read_write.c:795
 vfs_readv fs/read_write.c:915 [inline]
 do_preadv+0x159/0x230 fs/read_write.c:1007
 __do_sys_preadv fs/read_write.c:1057 [inline]
 __se_sys_preadv fs/read_write.c:1052 [inline]
 __x64_sys_preadv+0x58/0x60 fs/read_write.c:1052
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000ed6000 -> 0x0000000000ed8000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4187 Comm: syz-executor.3 Not tainted 6.7.0-rc8-syzkaller-00119-g1f874787ed9a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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