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BUG: KCSAN: data-race in shmem_getpage_gfp / shmem_setattr

write to 0xffff88813026dde0 of 8 bytes by task 23753 on cpu 0:
 i_size_write include/linux/fs.h:871 [inline]
 shmem_setattr+0x299/0x450 mm/shmem.c:1082
 notify_change+0x8a3/0xa80 fs/attr.c:398
 do_truncate fs/open.c:64 [inline]
 do_sys_ftruncate+0x405/0x4c0 fs/open.c:196
 __do_sys_ftruncate fs/open.c:207 [inline]
 __se_sys_ftruncate fs/open.c:205 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:205
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813026dde0 of 8 bytes by task 23750 on cpu 1:
 i_size_read include/linux/fs.h:849 [inline]
 shmem_getpage_gfp+0x1a5/0x1410 mm/shmem.c:1814
 shmem_fault+0x16d/0x500 mm/shmem.c:2116
 __do_fault mm/memory.c:3721 [inline]
 do_cow_fault mm/memory.c:4054 [inline]
 do_fault mm/memory.c:4155 [inline]
 handle_pte_fault mm/memory.c:4412 [inline]
 __handle_mm_fault mm/memory.c:4547 [inline]
 handle_mm_fault+0x128f/0x1a70 mm/memory.c:4645
 do_user_addr_fault+0x609/0xc00 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x91/0x230 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577

value changed: 0x0000000000000000 -> 0x0000000000208200

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23750 Comm: syz-executor.0 Tainted: G        W         5.13.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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