mm/huge_memory: refactor change_huge_pmd() non-present logic

Similar to copy_huge_pmd(), there is a large mass of open-coded logic for
the CONFIG_ARCH_ENABLE_THP_MIGRATION non-present entry case that does not
use thp_migration_supported() consistently.

Resolve this by separating out this logic and introduce
change_non_present_huge_pmd().

No functional change intended.

Link: https://lkml.kernel.org/r/451b85636ad711e307fdfbff19af699fdab4d05f.1762812360.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Heiko Carstens <hca@linux.ibm.com>
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: Janosch Frank <frankja@linux.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mathew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 39 insertions, 33 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3bf8d2bf9374..0fdb3be39e31 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2424,6 +2424,42 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 	return false;
 }
 
+static void change_non_present_huge_pmd(struct mm_struct *mm,
+		unsigned long addr, pmd_t *pmd, bool uffd_wp,
+		bool uffd_wp_resolve)
+{
+	swp_entry_t entry = pmd_to_swp_entry(*pmd);
+	struct folio *folio = pfn_swap_entry_folio(entry);
+	pmd_t newpmd;
+
+	VM_WARN_ON(!is_pmd_non_present_folio_entry(*pmd));
+	if (is_writable_migration_entry(entry)) {
+		/*
+		 * A protection check is difficult so
+		 * just be safe and disable write
+		 */
+		if (folio_test_anon(folio))
+			entry = make_readable_exclusive_migration_entry(swp_offset(entry));
+		else
+			entry = make_readable_migration_entry(swp_offset(entry));
+		newpmd = swp_entry_to_pmd(entry);
+		if (pmd_swp_soft_dirty(*pmd))
+			newpmd = pmd_swp_mksoft_dirty(newpmd);
+	} else if (is_writable_device_private_entry(entry)) {
+		entry = make_readable_device_private_entry(swp_offset(entry));
+		newpmd = swp_entry_to_pmd(entry);
+	} else {
+		newpmd = *pmd;
+	}
+
+	if (uffd_wp)
+		newpmd = pmd_swp_mkuffd_wp(newpmd);
+	else if (uffd_wp_resolve)
+		newpmd = pmd_swp_clear_uffd_wp(newpmd);
+	if (!pmd_same(*pmd, newpmd))
+		set_pmd_at(mm, addr, pmd, newpmd);
+}
+
 /*
  * Returns
  *  - 0 if PMD could not be locked
@@ -2452,41 +2488,11 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	if (!ptl)
 		return 0;
 
-#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
-	if (is_swap_pmd(*pmd)) {
-		swp_entry_t entry = pmd_to_swp_entry(*pmd);
-		struct folio *folio = pfn_swap_entry_folio(entry);
-		pmd_t newpmd;
-
-		VM_WARN_ON(!is_pmd_non_present_folio_entry(*pmd));
-		if (is_writable_migration_entry(entry)) {
-			/*
-			 * A protection check is difficult so
-			 * just be safe and disable write
-			 */
-			if (folio_test_anon(folio))
-				entry = make_readable_exclusive_migration_entry(swp_offset(entry));
-			else
-				entry = make_readable_migration_entry(swp_offset(entry));
-			newpmd = swp_entry_to_pmd(entry);
-			if (pmd_swp_soft_dirty(*pmd))
-				newpmd = pmd_swp_mksoft_dirty(newpmd);
-		} else if (is_writable_device_private_entry(entry)) {
-			entry = make_readable_device_private_entry(swp_offset(entry));
-			newpmd = swp_entry_to_pmd(entry);
-		} else {
-			newpmd = *pmd;
-		}
-
-		if (uffd_wp)
-			newpmd = pmd_swp_mkuffd_wp(newpmd);
-		else if (uffd_wp_resolve)
-			newpmd = pmd_swp_clear_uffd_wp(newpmd);
-		if (!pmd_same(*pmd, newpmd))
-			set_pmd_at(mm, addr, pmd, newpmd);
+	if (thp_migration_supported() && is_swap_pmd(*pmd)) {
+		change_non_present_huge_pmd(mm, addr, pmd, uffd_wp,
+					    uffd_wp_resolve);
 		goto unlock;
 	}
-#endif
 
 	if (prot_numa) {