syzbot

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BUG: KCSAN: data-race in __mark_inode_dirty / redirty_tail_locked

read-write to 0xffff8881080df728 of 8 bytes by task 6995 on cpu 0:
 redirty_tail_locked+0x56/0x270 fs/fs-writeback.c:1346
 requeue_inode fs/fs-writeback.c:1609 [inline]
 writeback_sb_inodes+0x903/0xb20 fs/fs-writeback.c:1976
 wb_writeback+0x25e/0x720 fs/fs-writeback.c:2127
 wb_do_writeback fs/fs-writeback.c:2274 [inline]
 wb_workfn+0x1a8/0x940 fs/fs-writeback.c:2314
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x700 kernel/workqueue.c:3390
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff8881080df728 of 8 bytes by task 8922 on cpu 1:
 __mark_inode_dirty+0x19f/0x7e0 fs/fs-writeback.c:2508
 mark_inode_dirty include/linux/fs.h:2426 [inline]
 generic_write_end+0x172/0x230 fs/buffer.c:2315
 fat_write_end+0x4e/0x160 fs/fat/inode.c:243
 cont_expand_zero fs/buffer.c:2519 [inline]
 cont_write_begin+0x2ca/0x6b0 fs/buffer.c:2577
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:229
 generic_cont_expand_simple+0xaa/0x150 fs/buffer.c:2478
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_setattr+0x2aa/0x840 fs/fat/file.c:513
 notify_change+0x814/0x8a0 fs/attr.c:495
 do_truncate fs/open.c:65 [inline]
 do_ftruncate+0x3e1/0x470 fs/open.c:181
 do_sys_ftruncate fs/open.c:199 [inline]
 __do_sys_ftruncate fs/open.c:207 [inline]
 __se_sys_ftruncate fs/open.c:205 [inline]
 __x64_sys_ftruncate+0x6a/0xc0 fs/open.c:205
 x64_sys_call+0x8e5/0x2d60 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

value changed: 0x0000000000020087 -> 0x0000000000000007

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8922 Comm: syz.2.1395 Tainted: G        W          6.11.0-rc2-syzkaller-00013-gd4560686726f #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
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FAT-fs (loop2): error, fat_get_cluster: invalid cluster chain (i_pos 1050)
FAT-fs (loop2): Filesystem has been set read-only
FAT-fs (loop2): error, fat_get_cluster: invalid cluster chain (i_pos 1050)
FAT-fs (loop2): error, fat_get_cluster: invalid cluster chain (i_pos 1050)