shmem: Convert shmem_add_to_page_cache to XArray

We can use xas_find_conflict() instead of radix_tree_gang_lookup_slot()
to find any conflicting entry and combine the three paths through this
function into one.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index a305529..8633bd3 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -577,9 +577,11 @@ static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
  */
 static int shmem_add_to_page_cache(struct page *page,
                                   struct address_space *mapping,
-                                  pgoff_t index, void *expected)
+                                  pgoff_t index, void *expected, gfp_t gfp)
 {
-       int error, nr = hpage_nr_pages(page);
+       XA_STATE_ORDER(xas, &mapping->i_pages, index, compound_order(page));
+       unsigned long i = 0;
+       unsigned long nr = 1UL << compound_order(page);
 
        VM_BUG_ON_PAGE(PageTail(page), page);
        VM_BUG_ON_PAGE(index != round_down(index, nr), page);
@@ -591,46 +593,39 @@ static int shmem_add_to_page_cache(struct page *page,
        page->mapping = mapping;
        page->index = index;
 
-       xa_lock_irq(&mapping->i_pages);
-       if (PageTransHuge(page)) {
-               void __rcu **results;
-               pgoff_t idx;
-               int i;
-
-               error = 0;
-               if (radix_tree_gang_lookup_slot(&mapping->i_pages,
-                                       &results, &idx, index, 1) &&
-                               idx < index + HPAGE_PMD_NR) {
-                       error = -EEXIST;
+       do {
+               void *entry;
+               xas_lock_irq(&xas);
+               entry = xas_find_conflict(&xas);
+               if (entry != expected)
+                       xas_set_err(&xas, -EEXIST);
+               xas_create_range(&xas);
+               if (xas_error(&xas))
+                       goto unlock;
+next:
+               xas_store(&xas, page + i);
+               if (++i < nr) {
+                       xas_next(&xas);
+                       goto next;
                }
-
-               if (!error) {
-                       for (i = 0; i < HPAGE_PMD_NR; i++) {
-                               error = radix_tree_insert(&mapping->i_pages,
-                                               index + i, page + i);
-                               VM_BUG_ON(error);
-                       }
+               if (PageTransHuge(page)) {
                        count_vm_event(THP_FILE_ALLOC);
+                       __inc_node_page_state(page, NR_SHMEM_THPS);
                }
-       } else if (!expected) {
-               error = radix_tree_insert(&mapping->i_pages, index, page);
-       } else {
-               error = shmem_replace_entry(mapping, index, expected, page);
-       }
-
-       if (!error) {
                mapping->nrpages += nr;
-               if (PageTransHuge(page))
-                       __inc_node_page_state(page, NR_SHMEM_THPS);
                __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
                __mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
-               xa_unlock_irq(&mapping->i_pages);
-       } else {
+unlock:
+               xas_unlock_irq(&xas);
+       } while (xas_nomem(&xas, gfp));
+
+       if (xas_error(&xas)) {
                page->mapping = NULL;
-               xa_unlock_irq(&mapping->i_pages);
                page_ref_sub(page, nr);
+               return xas_error(&xas);
        }
-       return error;
+
+       return 0;
 }
 
 /*
@@ -1183,7 +1178,7 @@ static int shmem_unuse_inode(struct shmem_inode_info *info,
         */
        if (!error)
                error = shmem_add_to_page_cache(*pagep, mapping, index,
-                                               radswap);
+                                               radswap, gfp);
        if (error != -ENOMEM) {
                /*
                 * Truncation and eviction use free_swap_and_cache(), which
@@ -1700,7 +1695,7 @@ repeat:
                                false);
                if (!error) {
                        error = shmem_add_to_page_cache(page, mapping, index,
-                                               swp_to_radix_entry(swap));
+                                               swp_to_radix_entry(swap), gfp);
                        /*
                         * We already confirmed swap under page lock, and make
                         * no memory allocation here, so usually no possibility
@@ -1806,13 +1801,8 @@ alloc_nohuge:            page = shmem_alloc_and_acct_page(gfp, inode,
                                PageTransHuge(page));
                if (error)
                        goto unacct;
-               error = radix_tree_maybe_preload_order(gfp & GFP_RECLAIM_MASK,
-                               compound_order(page));
-               if (!error) {
-                       error = shmem_add_to_page_cache(page, mapping, hindex,
-                                                       NULL);
-                       radix_tree_preload_end();
-               }
+               error = shmem_add_to_page_cache(page, mapping, hindex,
+                                               NULL, gfp & GFP_RECLAIM_MASK);
                if (error) {
                        mem_cgroup_cancel_charge(page, memcg,
                                        PageTransHuge(page));
@@ -2281,11 +2271,8 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
        if (ret)
                goto out_release;
 
-       ret = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
-       if (!ret) {
-               ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL);
-               radix_tree_preload_end();
-       }
+       ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL,
+                                               gfp & GFP_RECLAIM_MASK);
        if (ret)
                goto out_release_uncharge;