==================================================================
BUG: KCSAN: data-race in next_uptodate_page / shmem_write_end

write to 0xffff8881040e6498 of 8 bytes by task 19398 on cpu 1:
 i_size_write include/linux/fs.h:916 [inline]
 shmem_write_end+0x60/0x3d0 mm/shmem.c:2480
 generic_perform_write+0x251/0x3e0 mm/filemap.c:3781
 __generic_file_write_iter+0x174/0x310 mm/filemap.c:3897
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3929
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x63e/0xbb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1308 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0xb9/0x140 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881040e6498 of 8 bytes by task 19391 on cpu 0:
 i_size_read include/linux/fs.h:894 [inline]
 next_uptodate_page+0x323/0x670 mm/filemap.c:3256
 first_map_page mm/filemap.c:3273 [inline]
 filemap_map_pages+0xf7/0x880 mm/filemap.c:3299
 do_fault_around mm/memory.c:4151 [inline]
 do_read_fault mm/memory.c:4166 [inline]
 do_fault mm/memory.c:4300 [inline]
 handle_pte_fault mm/memory.c:4558 [inline]
 __handle_mm_fault mm/memory.c:4693 [inline]
 handle_mm_fault+0xb08/0x1580 mm/memory.c:4791
 do_user_addr_fault+0x609/0xbe0 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x91/0x220 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30

value changed: 0x0000000000001de8 -> 0x0000000000001df0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19391 Comm: syz-executor.1 Tainted: G        W         5.15.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================