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BUG: KCSAN: data-race in generic_file_direct_write / generic_file_read_iter

write to 0xffff888138a6b6e8 of 8 bytes by task 7787 on cpu 1:
 i_size_write include/linux/fs.h:871 [inline]
 generic_file_direct_write+0x391/0x400 mm/filemap.c:3730
 __generic_file_write_iter+0x11f/0x280 mm/filemap.c:3863
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3939
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:868
 vfs_iter_write+0x4c/0x70 fs/read_write.c:909
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1262
 __do_sys_sendfile64 fs/read_write.c:1327 [inline]
 __se_sys_sendfile64 fs/read_write.c:1313 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1313
 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+0x46/0xb0

read to 0xffff888138a6b6e8 of 8 bytes by task 7790 on cpu 0:
 i_size_read include/linux/fs.h:849 [inline]
 generic_file_read_iter+0x2e4/0x320 mm/filemap.c:2830
 call_read_iter include/linux/fs.h:2052 [inline]
 generic_file_splice_read+0x1de/0x2c0 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2ac/0x660 fs/splice.c:870
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1262
 __do_sys_sendfile64 fs/read_write.c:1327 [inline]
 __se_sys_sendfile64 fs/read_write.c:1313 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1313
 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+0x46/0xb0

value changed: 0x000000000000f600 -> 0x000000000000f800

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7790 Comm: syz-executor.2 Not tainted 5.19.0-rc4-syzkaller-00036-gd9b2ba67917c-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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