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BUG: KCSAN: data-race in filemap_fault / generic_write_end

write to 0xffff888129cffb98 of 8 bytes by task 8255 on cpu 0:
 i_size_write include/linux/fs.h:878 [inline]
 generic_write_end+0x99/0x230 fs/buffer.c:2183
 ext4_da_write_end+0x448/0x510 fs/ext4/inode.c:3068
 generic_perform_write+0x26d/0x400 mm/filemap.c:3804
 ext4_buffered_write_iter+0x199/0x280 fs/ext4/file.c:270
 ext4_file_write_iter+0x21a/0xd70
 call_write_iter include/linux/fs.h:2050 [inline]
 do_iter_readv_writev+0x27d/0x320 fs/read_write.c:726
 do_iter_write+0x192/0x5c0 fs/read_write.c:852
 vfs_iter_write+0x4c/0x70 fs/read_write.c:893
 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+0x675/0xc40 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1297
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888129cffb98 of 8 bytes by task 8266 on cpu 1:
 i_size_read include/linux/fs.h:856 [inline]
 filemap_fault+0x88/0x980 mm/filemap.c:3120
 __do_fault mm/memory.c:3915 [inline]
 do_cow_fault+0x226/0x800 mm/memory.c:4270
 do_fault mm/memory.c:4371 [inline]
 handle_pte_fault mm/memory.c:4627 [inline]
 __handle_mm_fault mm/memory.c:4763 [inline]
 handle_mm_fault+0x831/0xca0 mm/memory.c:4861
 faultin_page mm/gup.c:878 [inline]
 __get_user_pages+0x322/0xb70 mm/gup.c:1099
 populate_vma_page_range mm/gup.c:1442 [inline]
 __mm_populate+0x27a/0x390 mm/gup.c:1555
 mm_populate include/linux/mm.h:2701 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:524
 ksys_mmap_pgoff+0x265/0x320 mm/mmap.c:1628
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000035fa0 -> 0x0000000000036000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8266 Comm: syz-executor.0 Not tainted 5.18.0-rc1-syzkaller-00016-g3e732ebf7316-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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