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BUG: KCSAN: data-race in __filemap_add_folio / filemap_write_and_wait_range

read-write to 0xffff888106789460 of 8 bytes by task 5134 on cpu 1:
 __filemap_add_folio+0x430/0x6f0 mm/filemap.c:928
 filemap_add_folio+0x9c/0x1b0 mm/filemap.c:980
 __filemap_get_folio+0x346/0x690 mm/filemap.c:1979
 block_write_begin fs/buffer.c:2221 [inline]
 cont_write_begin+0x512/0x860 fs/buffer.c:2577
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 cont_expand_zero fs/buffer.c:2504 [inline]
 cont_write_begin+0x18b/0x860 fs/buffer.c:2567
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 generic_cont_expand_simple+0xaa/0x150 fs/buffer.c:2468
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_setattr+0x2aa/0x840 fs/fat/file.c:513
 notify_change+0x85c/0x8e0 fs/attr.c:552
 do_truncate fs/open.c:65 [inline]
 do_ftruncate+0x332/0x440 fs/open.c:192
 do_sys_ftruncate fs/open.c:207 [inline]
 __do_sys_ftruncate fs/open.c:212 [inline]
 __se_sys_ftruncate fs/open.c:210 [inline]
 __x64_sys_ftruncate+0x67/0xc0 fs/open.c:210
 x64_sys_call+0x9d9/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:78
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106789460 of 8 bytes by task 5139 on cpu 0:
 mapping_needs_writeback mm/filemap.c:643 [inline]
 filemap_write_and_wait_range+0x59/0x360 mm/filemap.c:692
 kiocb_write_and_wait mm/filemap.c:2791 [inline]
 generic_file_read_iter+0xff/0x330 mm/filemap.c:2865
 copy_splice_read+0x383/0x5b0 fs/splice.c:365
 do_splice_read fs/splice.c:984 [inline]
 splice_direct_to_actor+0x28b/0x670 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x398/0x660 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1424 [inline]
 __se_sys_sendfile64 fs/read_write.c:1410 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1410
 x64_sys_call+0xfbd/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000059 -> 0x000000000000005a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5139 Comm: syz.3.538 Not tainted 6.14.0-rc7-syzkaller-00202-g183601b78a9b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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