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BUG: KCSAN: data-race in filemap_fault / generic_write_end

write to 0xffff8881065840e8 of 8 bytes by task 27825 on cpu 0:
 i_size_write include/linux/fs.h:932 [inline]
 generic_write_end+0x94/0x230 fs/buffer.c:2292
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 cont_expand_zero fs/buffer.c:2517 [inline]
 cont_write_begin+0x2c0/0x690 fs/buffer.c:2575
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_cont_expand_simple+0xa7/0x140 fs/buffer.c:2476
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_fallocate+0x182/0x1d0 fs/fat/file.c:301
 vfs_fallocate+0x378/0x3e0 fs/open.c:324
 ksys_fallocate fs/open.c:347 [inline]
 __do_sys_fallocate fs/open.c:355 [inline]
 __se_sys_fallocate fs/open.c:353 [inline]
 __x64_sys_fallocate+0x79/0xc0 fs/open.c:353
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881065840e8 of 8 bytes by task 27824 on cpu 1:
 i_size_read include/linux/fs.h:910 [inline]
 filemap_fault+0x984/0xbf0 mm/filemap.c:3358
 __do_fault mm/memory.c:4204 [inline]
 do_shared_fault mm/memory.c:4635 [inline]
 do_fault mm/memory.c:4709 [inline]
 do_pte_missing mm/memory.c:3669 [inline]
 handle_pte_fault mm/memory.c:4978 [inline]
 __handle_mm_fault mm/memory.c:5119 [inline]
 handle_mm_fault+0x170f/0x2cc0 mm/memory.c:5284
 do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x2f7/0x6c0 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

value changed: 0x0000000000061000 -> 0x0000000000062000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27824 Comm: syz-executor.3 Not tainted 6.6.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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