1 files changed, 71 insertions, 97 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 40667c2f3383..1146fcfa3215 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -126,7 +126,7 @@ static void page_cache_delete(struct address_space *mapping,
         /* hugetlb pages are represented by a single entry in the xarray */
         if (!PageHuge(page)) {
                 xas_set_order(&xas, page->index, compound_order(page));
-                nr = 1U << compound_order(page);
+                nr = compound_nr(page);
         }
 
         VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -203,8 +203,9 @@ static void unaccount_page_cache_page(struct address_space *mapping,
                 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
                 if (PageTransHuge(page))
                         __dec_node_page_state(page, NR_SHMEM_THPS);
-        } else {
-                VM_BUG_ON_PAGE(PageTransHuge(page), page);
+        } else if (PageTransHuge(page)) {
+                __dec_node_page_state(page, NR_FILE_THPS);
+                filemap_nr_thps_dec(mapping);
         }
 
         /*
@@ -281,11 +282,11 @@ EXPORT_SYMBOL(delete_from_page_cache);
  * @pvec: pagevec with pages to delete
  *
  * The function walks over mapping->i_pages and removes pages passed in @pvec
- * from the mapping. The function expects @pvec to be sorted by page index.
+ * from the mapping. The function expects @pvec to be sorted by page index
+ * and is optimised for it to be dense.
  * It tolerates holes in @pvec (mapping entries at those indices are not
  * modified). The function expects only THP head pages to be present in the
- * @pvec and takes care to delete all corresponding tail pages from the
- * mapping as well.
+ * @pvec.
  *
  * The function expects the i_pages lock to be held.
  */
@@ -294,40 +295,43 @@ static void page_cache_delete_batch(struct address_space *mapping,
 {
         XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);
         int total_pages = 0;
-        int i = 0, tail_pages = 0;
+        int i = 0;
         struct page *page;
 
         mapping_set_update(&xas, mapping);
         xas_for_each(&xas, page, ULONG_MAX) {
-                if (i >= pagevec_count(pvec) && !tail_pages)
+                if (i >= pagevec_count(pvec))
                         break;
+
+                /* A swap/dax/shadow entry got inserted? Skip it. */
                 if (xa_is_value(page))
                         continue;
-                if (!tail_pages) {
-                        /*
-                         * Some page got inserted in our range? Skip it. We
-                         * have our pages locked so they are protected from
-                         * being removed.
-                         */
-                        if (page != pvec->pages[i]) {
-                                VM_BUG_ON_PAGE(page->index >
-                                                pvec->pages[i]->index, page);
-                                continue;
-                        }
-                        WARN_ON_ONCE(!PageLocked(page));
-                        if (PageTransHuge(page) && !PageHuge(page))
-                                tail_pages = HPAGE_PMD_NR - 1;
+                /*
+                 * A page got inserted in our range? Skip it. We have our
+                 * pages locked so they are protected from being removed.
+                 * If we see a page whose index is higher than ours, it
+                 * means our page has been removed, which shouldn't be
+                 * possible because we're holding the PageLock.
+                 */
+                if (page != pvec->pages[i]) {
+                        VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,
+                                        page);
+                        continue;
+                }
+
+                WARN_ON_ONCE(!PageLocked(page));
+
+                if (page->index == xas.xa_index)
                         page->mapping = NULL;
-                        /*
-                         * Leave page->index set: truncation lookup relies
-                         * upon it
-                         */
+                /* Leave page->index set: truncation lookup relies on it */
+
+                /*
+                 * Move to the next page in the vector if this is a regular
+                 * page or the index is of the last sub-page of this compound
+                 * page.
+                 */
+                if (page->index + compound_nr(page) - 1 == xas.xa_index)
                         i++;
-                } else {
-                        VM_BUG_ON_PAGE(page->index + HPAGE_PMD_NR - tail_pages
-                                        != pvec->pages[i]->index, page);
-                        tail_pages--;
-                }
                 xas_store(&xas, NULL);
                 total_pages++;
         }
@@ -408,7 +412,8 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
                 .range_end = end,
         };
 
-        if (!mapping_cap_writeback_dirty(mapping))
+        if (!mapping_cap_writeback_dirty(mapping) ||
+            !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
                 return 0;
 
         wbc_attach_fdatawrite_inode(&wbc, mapping->host);
@@ -617,10 +622,13 @@ int filemap_fdatawait_keep_errors(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
 
+/* Returns true if writeback might be needed or already in progress. */
 static bool mapping_needs_writeback(struct address_space *mapping)
 {
-        return (!dax_mapping(mapping) && mapping->nrpages) ||
-            (dax_mapping(mapping) && mapping->nrexceptional);
+        if (dax_mapping(mapping))
+                return mapping->nrexceptional;
+
+        return mapping->nrpages;
 }
 
 int filemap_write_and_wait(struct address_space *mapping)
@@ -1516,7 +1524,7 @@ EXPORT_SYMBOL(page_cache_prev_miss);
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
 {
         XA_STATE(xas, &mapping->i_pages, offset);
-        struct page *head, *page;
+        struct page *page;
 
         rcu_read_lock();
 repeat:
@@ -1531,25 +1539,19 @@ repeat:
         if (!page || xa_is_value(page))
                 goto out;
 
-        head = compound_head(page);
-        if (!page_cache_get_speculative(head))
+        if (!page_cache_get_speculative(page))
                 goto repeat;
 
-        /* The page was split under us? */
-        if (compound_head(page) != head) {
-                put_page(head);
-                goto repeat;
-        }
-
         /*
-         * Has the page moved?
+         * Has the page moved or been split?
          * This is part of the lockless pagecache protocol. See
          * include/linux/pagemap.h for details.
          */
         if (unlikely(page != xas_reload(&xas))) {
-                put_page(head);
+                put_page(page);
                 goto repeat;
         }
+        page = find_subpage(page, offset);
 out:
         rcu_read_unlock();
 
@@ -1646,7 +1648,7 @@ repeat:
                 }
 
                 /* Has the page been truncated? */
-                if (unlikely(page->mapping != mapping)) {
+                if (unlikely(compound_head(page)->mapping != mapping)) {
                         unlock_page(page);
                         put_page(page);
                         goto repeat;
@@ -1731,7 +1733,6 @@ unsigned find_get_entries(struct address_space *mapping,
 
         rcu_read_lock();
         xas_for_each(&xas, page, ULONG_MAX) {
-                struct page *head;
                 if (xas_retry(&xas, page))
                         continue;
                 /*
@@ -1742,17 +1743,13 @@ unsigned find_get_entries(struct address_space *mapping,
                 if (xa_is_value(page))
                         goto export;
 
-                head = compound_head(page);
-                if (!page_cache_get_speculative(head))
+                if (!page_cache_get_speculative(page))
                         goto retry;
 
-                /* The page was split under us? */
-                if (compound_head(page) != head)
-                        goto put_page;
-
-                /* Has the page moved? */
+                /* Has the page moved or been split? */
                 if (unlikely(page != xas_reload(&xas)))
                         goto put_page;
+                page = find_subpage(page, xas.xa_index);
 
 export:
                 indices[ret] = xas.xa_index;
@@ -1761,7 +1758,7 @@ export:
                         break;
                 continue;
 put_page:
-                put_page(head);
+                put_page(page);
 retry:
                 xas_reset(&xas);
         }
@@ -1803,33 +1800,27 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
 
         rcu_read_lock();
         xas_for_each(&xas, page, end) {
-                struct page *head;
                 if (xas_retry(&xas, page))
                         continue;
                 /* Skip over shadow, swap and DAX entries */
                 if (xa_is_value(page))
                         continue;
 
-                head = compound_head(page);
-                if (!page_cache_get_speculative(head))
+                if (!page_cache_get_speculative(page))
                         goto retry;
 
-                /* The page was split under us? */
-                if (compound_head(page) != head)
-                        goto put_page;
-
-                /* Has the page moved? */
+                /* Has the page moved or been split? */
                 if (unlikely(page != xas_reload(&xas)))
                         goto put_page;
 
-                pages[ret] = page;
+                pages[ret] = find_subpage(page, xas.xa_index);
                 if (++ret == nr_pages) {
                         *start = xas.xa_index + 1;
                         goto out;
                 }
                 continue;
 put_page:
-                put_page(head);
+                put_page(page);
 retry:
                 xas_reset(&xas);
         }
@@ -1874,7 +1865,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 
         rcu_read_lock();
         for (page = xas_load(&xas); page; page = xas_next(&xas)) {
-                struct page *head;
                 if (xas_retry(&xas, page))
                         continue;
                 /*
@@ -1884,24 +1874,19 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
                 if (xa_is_value(page))
                         break;
 
-                head = compound_head(page);
-                if (!page_cache_get_speculative(head))
+                if (!page_cache_get_speculative(page))
                         goto retry;
 
-                /* The page was split under us? */
-                if (compound_head(page) != head)
-                        goto put_page;
-
-                /* Has the page moved? */
+                /* Has the page moved or been split? */
                 if (unlikely(page != xas_reload(&xas)))
                         goto put_page;
 
-                pages[ret] = page;
+                pages[ret] = find_subpage(page, xas.xa_index);
                 if (++ret == nr_pages)
                         break;
                 continue;
 put_page:
-                put_page(head);
+                put_page(page);
 retry:
                 xas_reset(&xas);
         }
@@ -1937,7 +1922,6 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
 
         rcu_read_lock();
         xas_for_each_marked(&xas, page, end, tag) {
-                struct page *head;
                 if (xas_retry(&xas, page))
                         continue;
                 /*
@@ -1948,26 +1932,21 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
                 if (xa_is_value(page))
                         continue;
 
-                head = compound_head(page);
-                if (!page_cache_get_speculative(head))
+                if (!page_cache_get_speculative(page))
                         goto retry;
 
-                /* The page was split under us? */
-                if (compound_head(page) != head)
-                        goto put_page;
-
-                /* Has the page moved? */
+                /* Has the page moved or been split? */
                 if (unlikely(page != xas_reload(&xas)))
                         goto put_page;
 
-                pages[ret] = page;
+                pages[ret] = find_subpage(page, xas.xa_index);
                 if (++ret == nr_pages) {
                         *index = xas.xa_index + 1;
                         goto out;
                 }
                 continue;
 put_page:
-                put_page(head);
+                put_page(page);
 retry:
                 xas_reset(&xas);
         }
@@ -2562,12 +2541,12 @@ retry_find:
                 goto out_retry;
 
         /* Did it get truncated? */
-        if (unlikely(page->mapping != mapping)) {
+        if (unlikely(compound_head(page)->mapping != mapping)) {
                 unlock_page(page);
                 put_page(page);
                 goto retry_find;
         }
-        VM_BUG_ON_PAGE(page->index != offset, page);
+        VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
 
         /*
          * We have a locked page in the page cache, now we need to check
@@ -2648,7 +2627,7 @@ void filemap_map_pages(struct vm_fault *vmf,
         pgoff_t last_pgoff = start_pgoff;
         unsigned long max_idx;
         XA_STATE(xas, &mapping->i_pages, start_pgoff);
-        struct page *head, *page;
+        struct page *page;
 
         rcu_read_lock();
         xas_for_each(&xas, page, end_pgoff) {
@@ -2657,24 +2636,19 @@ void filemap_map_pages(struct vm_fault *vmf,
                 if (xa_is_value(page))
                         goto next;
 
-                head = compound_head(page);
-
                 /*
                  * Check for a locked page first, as a speculative
                  * reference may adversely influence page migration.
                  */
-                if (PageLocked(head))
+                if (PageLocked(page))
                         goto next;
-                if (!page_cache_get_speculative(head))
+                if (!page_cache_get_speculative(page))
                         goto next;
 
-                /* The page was split under us? */
-                if (compound_head(page) != head)
-                        goto skip;
-
-                /* Has the page moved? */
+                /* Has the page moved or been split? */
                 if (unlikely(page != xas_reload(&xas)))
                         goto skip;
+                page = find_subpage(page, xas.xa_index);
 
                 if (!PageUptodate(page) ||
                                 PageReadahead(page) ||