CVE-2025-39868: erofs: fix runtime warning on truncate_folio_batch_exceptionals()
In the Linux kernel, the following vulnerability has been resolved:

erofs: fix runtime warning on truncate_folio_batch_exceptionals()

Commit 0e2f80afcfa6("fs/dax: ensure all pages are idle prior to
filesystem unmount") introduced the WARN_ON_ONCE to capture whether
the filesystem has removed all DAX entries or not and applied the
fix to xfs and ext4.

Apply the missed fix on erofs to fix the runtime warning:

[  5.266254] ------------[ cut here ]------------
[  5.266274] WARNING: CPU: 6 PID: 3109 at mm/truncate.c:89 truncate_folio_batch_exceptionals+0xff/0x260
[  5.266294] Modules linked in:
[  5.266999] CPU: 6 UID: 0 PID: 3109 Comm: umount Tainted: G S                  6.16.0+ #6 PREEMPT(voluntary)
[  5.267012] Tainted: [S]=CPU_OUT_OF_SPEC
[  5.267017] Hardware name: Dell Inc. OptiPlex 5000/05WXFV, BIOS 1.5.1 08/24/2022
[  5.267024] RIP: 0010:truncate_folio_batch_exceptionals+0xff/0x260
[  5.267076] Code: 00 00 41 39 df 7f 11 eb 78 83 c3 01 49 83 c4 08 41 39 df 74 6c 48 63 f3 48 83 fe 1f 0f 83 3c 01 00 00 43 f6 44 26 08 01 74 df <0f> 0b 4a 8b 34 22 4c 89 ef 48 89 55 90 e8 ff 54 1f 00 48 8b 55 90
[  5.267083] RSP: 0018:ffffc900013f36c8 EFLAGS: 00010202
[  5.267095] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  5.267101] RDX: ffffc900013f3790 RSI: 0000000000000000 RDI: ffff8882a1407898
[  5.267108] RBP: ffffc900013f3740 R08: 0000000000000000 R09: 0000000000000000
[  5.267113] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[  5.267119] R13: ffff8882a1407ab8 R14: ffffc900013f3888 R15: 0000000000000001
[  5.267125] FS:  00007aaa8b437800(0000) GS:ffff88850025b000(0000) knlGS:0000000000000000
[  5.267132] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  5.267138] CR2: 00007aaa8b3aac10 CR3: 000000024f764000 CR4: 0000000000f52ef0
[  5.267144] PKRU: 55555554
[  5.267150] Call Trace:
[  5.267154]  <TASK>
[  5.267181]  truncate_inode_pages_range+0x118/0x5e0
[  5.267193]  ? save_trace+0x54/0x390
[  5.267296]  truncate_inode_pages_final+0x43/0x60
[  5.267309]  evict+0x2a4/0x2c0
[  5.267339]  dispose_list+0x39/0x80
[  5.267352]  evict_inodes+0x150/0x1b0
[  5.267376]  generic_shutdown_super+0x41/0x180
[  5.267390]  kill_block_super+0x1b/0x50
[  5.267402]  erofs_kill_sb+0x81/0x90 [erofs]
[  5.267436]  deactivate_locked_super+0x32/0xb0
[  5.267450]  deactivate_super+0x46/0x60
[  5.267460]  cleanup_mnt+0xc3/0x170
[  5.267475]  __cleanup_mnt+0x12/0x20
[  5.267485]  task_work_run+0x5d/0xb0
[  5.267499]  exit_to_user_mode_loop+0x144/0x170
[  5.267512]  do_syscall_64+0x2b9/0x7c0
[  5.267523]  ? __lock_acquire+0x665/0x2ce0
[  5.267535]  ? __lock_acquire+0x665/0x2ce0
[  5.267560]  ? lock_acquire+0xcd/0x300
[  5.267573]  ? find_held_lock+0x31/0x90
[  5.267582]  ? mntput_no_expire+0x97/0x4e0
[  5.267606]  ? mntput_no_expire+0xa1/0x4e0
[  5.267625]  ? mntput+0x24/0x50
[  5.267634]  ? path_put+0x1e/0x30
[  5.267647]  ? do_faccessat+0x120/0x2f0
[  5.267677]  ? do_syscall_64+0x1a2/0x7c0
[  5.267686]  ? from_kgid_munged+0x17/0x30
[  5.267703]  ? from_kuid_munged+0x13/0x30
[  5.267711]  ? __do_sys_getuid+0x3d/0x50
[  5.267724]  ? do_syscall_64+0x1a2/0x7c0
[  5.267732]  ? irqentry_exit+0x77/0xb0
[  5.267743]  ? clear_bhb_loop+0x30/0x80
[  5.267752]  ? clear_bhb_loop+0x30/0x80
[  5.267765]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  5.267772] RIP: 0033:0x7aaa8b32a9fb
[  5.267781] Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 e9 83 0d 00 f7 d8
[  5.267787] RSP: 002b:00007ffd7c4c9468 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
[  5.267796] RAX: 0000000000000000 RBX: 00005a61592a8b00 RCX: 00007aaa8b32a9fb
[  5.267802] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00005a61592b2080
[  5.267806] RBP: 00007ffd7c4c9540 R08: 00007aaa8b403b20 R09: 0000000000000020
[  5.267812] R10: 0000000000000001 R11: 0000000000000246 R12: 00005a61592a8c00
[  5.267817] R13: 00000000
---truncated---
CVSS v3.1: 7.8