syzbot

==================================================================
BUG: KCSAN: data-race in __mark_inode_dirty / __mark_inode_dirty

write to 0xffff888109b25328 of 4 bytes by task 3909 on cpu 1:
 __mark_inode_dirty+0x248/0x750 fs/fs-writeback.c:2558
 mark_buffer_dirty+0x133/0x210 fs/buffer.c:1209
 block_commit_write fs/buffer.c:2218 [inline]
 block_write_end+0x12d/0x210 fs/buffer.c:2294
 generic_write_end+0x56/0x150 fs/buffer.c:2308
 fat_write_end+0x4f/0x160 fs/fat/inode.c:244
 generic_perform_write+0x312/0x490 mm/filemap.c:4196
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4292
 generic_file_write_iter+0x8d/0x2f0 mm/filemap.c:4318
 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 0xffff888109b25328 of 4 bytes by task 3901 on cpu 0:
 __mark_inode_dirty+0x55/0x750 fs/fs-writeback.c:2509
 fat_update_time+0x1ec/0x200 fs/fat/misc.c:357
 inode_update_time fs/inode.c:2075 [inline]
 touch_atime+0x148/0x340 fs/inode.c:2148
 file_accessed include/linux/fs.h:2663 [inline]
 filemap_splice_read+0x6ba/0x740 mm/filemap.c:3047
 do_splice_read fs/splice.c:982 [inline]
 splice_direct_to_actor+0x26f/0x680 fs/splice.c:1086
 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: 0x00000008 -> 0x00000038

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3901 Comm: syz.0.87 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================