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BUG: KCSAN: data-race in next_uptodate_page / shmem_write_end

write to 0xffff88813cf224d8 of 8 bytes by task 25707 on cpu 0:
 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]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x7bc/0x900 fs/read_write.c:594
 ksys_write+0xd9/0x190 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:656
 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 0xffff88813cf224d8 of 8 bytes by task 25712 on cpu 1:
 i_size_read include/linux/fs.h:894 [inline]
 next_uptodate_page+0x323/0x670 mm/filemap.c:3256
 next_map_page mm/filemap.c:3281 [inline]
 filemap_map_pages+0x771/0x880 mm/filemap.c:3337
 do_fault_around mm/memory.c:4152 [inline]
 do_read_fault mm/memory.c:4167 [inline]
 do_fault mm/memory.c:4301 [inline]
 handle_pte_fault mm/memory.c:4559 [inline]
 __handle_mm_fault mm/memory.c:4694 [inline]
 handle_mm_fault+0xb08/0x1580 mm/memory.c:4792
 faultin_page mm/gup.c:937 [inline]
 __get_user_pages+0x381/0xc50 mm/gup.c:1158
 populate_vma_page_range mm/gup.c:1490 [inline]
 __mm_populate+0x24d/0x370 mm/gup.c:1599
 mm_populate include/linux/mm.h:2624 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:524
 ksys_mmap_pgoff+0x284/0x350 mm/mmap.c:1624
 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

value changed: 0x0000000000c85000 -> 0x0000000000c8b000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25712 Comm: syz-executor.4 Tainted: G        W         5.15.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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