huge_memory: convert do_huge_pmd_wp_page() to use a folio

Removes many calls to compound_head().  Does not remove the assumption
that a folio may not be larger than a PMD.

Link: https://lkml.kernel.org/r/20220902194653.1739778-43-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 84bf1d5..1181e62 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1305,6 +1305,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
 {
        const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
        struct vm_area_struct *vma = vmf->vma;
+       struct folio *folio;
        struct page *page;
        unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
        pmd_t orig_pmd = vmf->orig_pmd;
@@ -1326,46 +1327,48 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
        }
 
        page = pmd_page(orig_pmd);
+       folio = page_folio(page);
        VM_BUG_ON_PAGE(!PageHead(page), page);
 
        /* Early check when only holding the PT lock. */
        if (PageAnonExclusive(page))
                goto reuse;
 
-       if (!trylock_page(page)) {
-               get_page(page);
+       if (!folio_trylock(folio)) {
+               folio_get(folio);
                spin_unlock(vmf->ptl);
-               lock_page(page);
+               folio_lock(folio);
                spin_lock(vmf->ptl);
                if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
                        spin_unlock(vmf->ptl);
-                       unlock_page(page);
-                       put_page(page);
+                       folio_unlock(folio);
+                       folio_put(folio);
                        return 0;
                }
-               put_page(page);
+               folio_put(folio);
        }
 
        /* Recheck after temporarily dropping the PT lock. */
        if (PageAnonExclusive(page)) {
-               unlock_page(page);
+               folio_unlock(folio);
                goto reuse;
        }
 
        /*
-        * See do_wp_page(): we can only reuse the page exclusively if there are
-        * no additional references. Note that we always drain the LRU
-        * pagevecs immediately after adding a THP.
+        * See do_wp_page(): we can only reuse the folio exclusively if
+        * there are no additional references. Note that we always drain
+        * the LRU pagevecs immediately after adding a THP.
         */
-       if (page_count(page) > 1 + PageSwapCache(page) * thp_nr_pages(page))
+       if (folio_ref_count(folio) >
+                       1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
                goto unlock_fallback;
-       if (PageSwapCache(page))
-               try_to_free_swap(page);
-       if (page_count(page) == 1) {
+       if (folio_test_swapcache(folio))
+               folio_free_swap(folio);
+       if (folio_ref_count(folio) == 1) {
                pmd_t entry;
 
                page_move_anon_rmap(page, vma);
-               unlock_page(page);
+               folio_unlock(folio);
 reuse:
                if (unlikely(unshare)) {
                        spin_unlock(vmf->ptl);
@@ -1380,7 +1383,7 @@ reuse:
        }
 
 unlock_fallback:
-       unlock_page(page);
+       folio_unlock(folio);
        spin_unlock(vmf->ptl);
 fallback:
        __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);