syzbot

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BUG: KCSAN: data-race in __filemap_add_folio / filemap_write_and_wait_range

read-write to 0xffff88811da242d8 of 8 bytes by task 7034 on cpu 0:
 __filemap_add_folio+0x5b9/0x7d0 mm/filemap.c:928
 filemap_add_folio+0x98/0x1b0 mm/filemap.c:969
 __filemap_get_folio+0x31e/0x6b0 mm/filemap.c:1991
 write_begin_get_folio include/linux/pagemap.h:776 [inline]
 ext4_write_begin+0x2fe/0xeb0 fs/ext4/inode.c:1318
 generic_perform_write+0x181/0x490 mm/filemap.c:4175
 ext4_buffered_write_iter+0x1ee/0x3c0 fs/ext4/file.c:299
 ext4_dio_write_iter fs/ext4/file.c:613 [inline]
 ext4_file_write_iter+0xdbf/0xf00 fs/ext4/file.c:721
 iter_file_splice_write+0x663/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x153/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x30f/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811da242d8 of 8 bytes by task 7038 on cpu 1:
 mapping_needs_writeback mm/filemap.c:641 [inline]
 filemap_write_and_wait_range+0x59/0x340 mm/filemap.c:690
 ext4_dio_write_iter fs/ext4/file.c:626 [inline]
 ext4_file_write_iter+0xe04/0xf00 fs/ext4/file.c:721
 iter_file_splice_write+0x663/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x153/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x30f/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000000000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7038 Comm: syz.0.859 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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