shmem: convert shmem_mfill_atomic_pte() to use a folio

Assert that this is a single-page folio as there are several assumptions
in here that it's exactly PAGE_SIZE bytes large.  Saves several calls to
compound_head() and removes the last caller of shmem_alloc_page().

Link: https://lkml.kernel.org/r/20220902194653.1739778-18-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/shmem.c b/mm/shmem.c
index 56cabf9bb947bf275d4ceb3468b9e3ade786aeb5..8754e2b4800a1120b92dae9f7d27d62cc8d89325 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2374,12 +2374,6 @@ static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
 }
 
 #ifdef CONFIG_USERFAULTFD
-static struct page *shmem_alloc_page(gfp_t gfp,
-                       struct shmem_inode_info *info, pgoff_t index)
-{
-       return &shmem_alloc_folio(gfp, info, index)->page;
-}
-
 int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
                           pmd_t *dst_pmd,
                           struct vm_area_struct *dst_vma,
@@ -2395,7 +2389,6 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
        pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
        void *page_kaddr;
        struct folio *folio;
-       struct page *page;
        int ret;
        pgoff_t max_off;
 
@@ -2414,53 +2407,53 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 
        if (!*pagep) {
                ret = -ENOMEM;
-               page = shmem_alloc_page(gfp, info, pgoff);
-               if (!page)
+               folio = shmem_alloc_folio(gfp, info, pgoff);
+               if (!folio)
                        goto out_unacct_blocks;
 
                if (!zeropage) {        /* COPY */
-                       page_kaddr = kmap_atomic(page);
+                       page_kaddr = kmap_local_folio(folio, 0);
                        ret = copy_from_user(page_kaddr,
                                             (const void __user *)src_addr,
                                             PAGE_SIZE);
-                       kunmap_atomic(page_kaddr);
+                       kunmap_local(page_kaddr);
 
                        /* fallback to copy_from_user outside mmap_lock */
                        if (unlikely(ret)) {
-                               *pagep = page;
+                               *pagep = &folio->page;
                                ret = -ENOENT;
                                /* don't free the page */
                                goto out_unacct_blocks;
                        }
 
-                       flush_dcache_page(page);
+                       flush_dcache_folio(folio);
                } else {                /* ZEROPAGE */
-                       clear_user_highpage(page, dst_addr);
+                       clear_user_highpage(&folio->page, dst_addr);
                }
        } else {
-               page = *pagep;
+               folio = page_folio(*pagep);
+               VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
                *pagep = NULL;
        }
 
-       VM_BUG_ON(PageLocked(page));
-       VM_BUG_ON(PageSwapBacked(page));
-       __SetPageLocked(page);
-       __SetPageSwapBacked(page);
-       __SetPageUptodate(page);
+       VM_BUG_ON(folio_test_locked(folio));
+       VM_BUG_ON(folio_test_swapbacked(folio));
+       __folio_set_locked(folio);
+       __folio_set_swapbacked(folio);
+       __folio_mark_uptodate(folio);
 
        ret = -EFAULT;
        max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
        if (unlikely(pgoff >= max_off))
                goto out_release;
 
-       folio = page_folio(page);
        ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
                                      gfp & GFP_RECLAIM_MASK, dst_mm);
        if (ret)
                goto out_release;
 
        ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
-                                      page, true, wp_copy);
+                                      &folio->page, true, wp_copy);
        if (ret)
                goto out_delete_from_cache;
 
@@ -2470,13 +2463,13 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
        shmem_recalc_inode(inode);
        spin_unlock_irq(&info->lock);
 
-       unlock_page(page);
+       folio_unlock(folio);
        return 0;
 out_delete_from_cache:
-       delete_from_page_cache(page);
+       filemap_remove_folio(folio);
 out_release:
-       unlock_page(page);
-       put_page(page);
+       folio_unlock(folio);
+       folio_put(folio);
 out_unacct_blocks:
        shmem_inode_unacct_blocks(inode, 1);
        return ret;