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BUG: KCSAN: data-race in filemap_read / generic_write_end

write to 0xffff888109a9d9e8 of 8 bytes by task 4179 on cpu 1:
 i_size_write include/linux/fs.h:905 [inline]
 generic_write_end+0xb4/0x360 fs/buffer.c:2241
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 generic_perform_write+0x253/0x3d0 mm/filemap.c:3934
 __generic_file_write_iter+0xe6/0x290 mm/filemap.c:4051
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4083
 do_iter_write+0x4ae/0x770 fs/read_write.c:860
 vfs_iter_write+0x50/0x70 fs/read_write.c:901
 iter_file_splice_write+0x456/0x7d0 fs/splice.c:779
 do_splice_from fs/splice.c:857 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:1023
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:978
 do_splice_direct+0x104/0x180 fs/splice.c:1066
 do_sendfile+0x3b8/0x950 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1316 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1308
 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 0xffff888109a9d9e8 of 8 bytes by task 4186 on cpu 0:
 i_size_read include/linux/fs.h:883 [inline]
 filemap_read+0x247/0x680 mm/filemap.c:2703
 generic_file_read_iter+0x76/0x320 mm/filemap.c:2837
 call_read_iter include/linux/fs.h:1862 [inline]
 generic_file_splice_read+0xe3/0x290 fs/splice.c:403
 do_splice_to fs/splice.c:886 [inline]
 splice_direct_to_actor+0x25a/0x5f0 fs/splice.c:957
 do_splice_direct+0x104/0x180 fs/splice.c:1066
 do_sendfile+0x3b8/0x950 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 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

value changed: 0x00000000000032a2 -> 0x00000000000032b8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4186 Comm: syz-executor.3 Not tainted 6.3.0-syzkaller-13390-g2e1e1337881b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
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