mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp()

try_collapse_pte_mapped_thp() drops the PTE lock after it has cleared the
page table, and takes the PMD lock and the PTE lock to remove it.

In between, MADV_DONTNEED with CONFIG_PT_RECLAIM can reclaim the
page table. The pmd_same() check is supposed to handle this, but it is
only done with CONFIG_SPLIT_PTE_PTLOCKS.

Fix it by performing the check unconditionally.

Fix generated by an LLM and sent by Josef Bacik in private.

Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)")
Cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ david: adjust description ]
Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>
Tested-by: Gregory Price (Meta) <gourry@gourry.net>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Link: https://patch.msgid.link/20261031-fixes_core-v3-15-d6437171ecc3@kernel.org
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

0 files changed, 0 insertions, 0 deletions