mm/hwpoison: clear MF_COUNT_INCREASED before retrying get_any_page()

Hulk Robot reported a panic in put_page_testzero() when testing madvise()
with MADV_SOFT_OFFLINE.  The BUG() is triggered when retrying
get_any_page().  This is because we keep MF_COUNT_INCREASED flag in second
try but the refcnt is not increased.

 page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
 ------------[ cut here ]------------
 kernel BUG at include/linux/mm.h:737!
 invalid opcode: 0000 [#1] PREEMPT SMP
 CPU: 5 PID: 2135 Comm: sshd Tainted: G    B             5.16.0-rc6-dirty torvalds#373
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
 RIP: 0010:release_pages+0x53f/0x840
 Code: 0c 01 4c 8d 60 ff e9 5b fb ff ff 48 c7 c6 d8 97 0c b3 4c 89 e7 48 83 05 0e 7b 3c 0c 01 e8 89 3d 04 00 48 83 05 11 7b 3c 0c 01 <0f> 0b 48 83 05 0f 7b 3c 0c 01 48 83 05 0f 7b 3c 0c 01 48 83 05f
 RSP: 0018:ffffc900015a7bc0 EFLAGS: 00010002
 RAX: 000000000000003e RBX: ffffffffbace04c8 RCX: 0000000000000002
 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
 RBP: ffff88817b9acd50 R08: 0000000000000000 R09: c0000000ffefffff
 R10: 0000000000000001 R11: ffffc900015a79b0 R12: ffffea0005e1c900
 R13: ffffea0005e1de88 R14: 000000000000001f R15: ffff888100071000
 FS:  0000000000000000(0000) GS:ffff88842fb40000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f305e8de3d4 CR3: 000000017bb6f000 CR4: 00000000000006e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  <TASK>
  free_pages_and_swap_cache+0x64/0x80
  tlb_flush_mmu+0x6f/0x220
  unmap_page_range+0xe6c/0x12c0
  unmap_single_vma+0x90/0x170
  unmap_vmas+0xc4/0x180
  exit_mmap+0xde/0x3a0
  mmput+0xa3/0x250
  do_exit+0x564/0x1470
  do_group_exit+0x3b/0x100
  __do_sys_exit_group+0x13/0x20
  __x64_sys_exit_group+0x16/0x20
  do_syscall_64+0x34/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae
 RIP: 0033:0x7f30625401d9
 Code: Unable to access opcode bytes at RIP 0x7f30625401af.
 RSP: 002b:00007ffe391b0c88 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
 RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f30625401d9
 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000001
 RBP: 00007f306283d838 R08: 000000000000003c R09: 00000000000000e7
 R10: fffffffffffffe30 R11: 0000000000000246 R12: 00007f306283d838
 R13: 00007f3062842e80 R14: 0000000000000000 R15: ffffaa4fb7932430
  </TASK>
 Modules linked in:
 ---[ end trace e99579b570fe0649 ]---
 RIP: 0010:release_pages+0x53f/0x840
 Code: 0c 01 4c 8d 60 ff e9 5b fb ff ff 48 c7 c6 d8 97 0c b3 4c 89 e7 48 83 05 0e 7b 3c 0c 01 e8 89 3d 04 00 48 83 05 11 7b 3c 0c 01 <0f> 0b 48 83 05 0f 7b 3c 0c 01 48 83 05 0f 7b 3c 0c 01 48 83 05f
 RSP: 0018:ffffc900015a7bc0 EFLAGS: 00010002
 RAX: 000000000000003e RBX: ffffffffbace04c8 RCX: 0000000000000002
 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
 RBP: ffff88817b9acd50 R08: 0000000000000000 R09: c0000000ffefffff
 R10: 0000000000000001 R11: ffffc900015a79b0 R12: ffffea0005e1c900
 R13: ffffea0005e1de88 R14: 000000000000001f R15: ffff888100071000
 FS:  0000000000000000(0000) GS:ffff88842fb40000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f305e8de3d4 CR3: 000000017bb6f000 CR4: 00000000000006e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Link: https://lkml.kernel.org/r/[email protected]
Fixes: b94e028 ("mm,hwpoison: try to narrow window race for free pages")
Signed-off-by: Liu Shixin <[email protected]>
Reported-by: Hulk Robot <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>

Author: Liu Shixin

mm/memory-failure.c

@@ -2234,6 +2234,7 @@ int soft_offline_page(unsigned long pfn, int flags)
 	} else if (ret == 0) {
 		if (soft_offline_free_page(page) && try_again) {
 			try_again = false;
+			flags &= ~MF_COUNT_INCREASED;
 			goto retry;
 		}
 	}