mm/khugepaged: introduce collapse_possible_orders helper functions

Add collapse_possible_orders() to generalize THP order eligibility.  The
function determines which THP orders are permitted based on collapse
context (khugepaged vs madv_collapse).  We also add collapse_possible() as
a thin wrapper around collapse_possible_orders() that returns a bool
rather than the whole bitmap.

This consolidates collapse configuration logic and provides a clean
interface for future mTHP collapse support where the orders may be
different.

Link: https://lore.kernel.org/20260605161422.213817-11-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e4872fdd3e8d64159e65f700d95cb1ffa28923ea..a763d46914bbb90ca4081ec919c18186e4dedc4e 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -554,12 +554,30 @@ void __khugepaged_enter(struct mm_struct *mm)
                wake_up_interruptible(&khugepaged_wait);
 }
 
+/*
+ * Check what orders are possible based on the vma and collapse type.
+ * This is used to determine if mTHP collapse is a viable option.
+ */
+static unsigned long collapse_possible_orders(struct vm_area_struct *vma,
+               vm_flags_t vm_flags, enum tva_type tva_flags)
+{
+       const unsigned long orders = BIT(HPAGE_PMD_ORDER);
+
+       return thp_vma_allowable_orders(vma, vm_flags, tva_flags, orders);
+}
+
+static bool collapse_possible(struct vm_area_struct *vma,
+               vm_flags_t vm_flags, enum tva_type tva_flags)
+{
+       return collapse_possible_orders(vma, vm_flags, tva_flags);
+}
+
 void khugepaged_enter_vma(struct vm_area_struct *vma,
                          vm_flags_t vm_flags)
 {
        if (!mm_flags_test(MMF_VM_HUGEPAGE, vma->vm_mm) &&
            hugepage_pmd_enabled()) {
-               if (thp_vma_allowable_order(vma, vm_flags, TVA_KHUGEPAGED, PMD_ORDER))
+               if (collapse_possible(vma, vm_flags, TVA_KHUGEPAGED))
                        __khugepaged_enter(vma->vm_mm);
        }
 }
@@ -2705,7 +2723,7 @@ static void collapse_scan_mm_slot(unsigned int progress_max,
                        cc->progress++;
                        break;
                }
-               if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER)) {
+               if (!collapse_possible(vma, vma->vm_flags, TVA_KHUGEPAGED)) {
                        cc->progress++;
                        continue;
                }
@@ -3015,7 +3033,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
        BUG_ON(vma->vm_start > start);
        BUG_ON(vma->vm_end < end);
 
-       if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_FORCED_COLLAPSE, PMD_ORDER))
+       if (!collapse_possible(vma, vma->vm_flags, TVA_FORCED_COLLAPSE))
                return -EINVAL;
 
        cc = kmalloc_obj(*cc);