Transparent Huge Pages are currently stored in i_pages as pointers to consecutive subpages. This patch changes that to storing consecutive pointers to the head page in preparation for storing huge pages more efficiently in i_pages.
Large parts of this are "inspired" by Kirill's patch https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shute...@linux.intel.com/ Signed-off-by: Matthew Wilcox <wi...@infradead.org> --- include/linux/pagemap.h | 9 ++++ mm/filemap.c | 96 +++++++++++++---------------------------- mm/khugepaged.c | 4 +- mm/shmem.c | 2 +- mm/swap_state.c | 2 +- 5 files changed, 42 insertions(+), 71 deletions(-) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 226f96f0dee06..41bf976574e74 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -345,6 +345,15 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping, mapping_gfp_mask(mapping)); } +static inline struct page *find_subpage(struct page *page, pgoff_t offset) +{ + VM_BUG_ON_PAGE(PageTail(page), page); + VM_BUG_ON_PAGE(page->index > offset, page); + VM_BUG_ON_PAGE(page->index + (1 << compound_order(page)) <= offset, + page); + return page - page->index + offset; +} + struct page *find_get_entry(struct address_space *mapping, pgoff_t offset); struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset); unsigned find_get_entries(struct address_space *mapping, pgoff_t start, diff --git a/mm/filemap.c b/mm/filemap.c index 538531590ef2d..d7274591381ac 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1407,7 +1407,7 @@ 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: @@ -1422,25 +1422,19 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t offset) if (!page || xa_is_value(page)) goto out; - head = compound_head(page); - if (!page_cache_get_speculative(head)) - goto repeat; - - /* The page was split under us? */ - if (compound_head(page) != head) { - put_page(head); + if (!page_cache_get_speculative(page)) 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(); @@ -1611,7 +1605,6 @@ 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; /* @@ -1622,17 +1615,13 @@ 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; @@ -1641,7 +1630,7 @@ unsigned find_get_entries(struct address_space *mapping, break; continue; put_page: - put_page(head); + put_page(page); retry: xas_reset(&xas); } @@ -1683,33 +1672,27 @@ 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 = page->index + 1; goto out; } continue; put_page: - put_page(head); + put_page(page); retry: xas_reset(&xas); } @@ -1754,7 +1737,6 @@ 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; /* @@ -1764,24 +1746,19 @@ 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); } @@ -1815,7 +1792,6 @@ 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; /* @@ -1826,26 +1802,21 @@ 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 = page->index + 1; goto out; } continue; put_page: - put_page(head); + put_page(page); retry: xas_reset(&xas); } @@ -1892,7 +1863,6 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, rcu_read_lock(); xas_for_each_marked(&xas, page, ULONG_MAX, tag) { - struct page *head; if (xas_retry(&xas, page)) continue; /* @@ -1903,17 +1873,13 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, 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; @@ -1922,7 +1888,7 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, break; continue; put_page: - put_page(head); + put_page(page); retry: xas_reset(&xas); } @@ -2533,7 +2499,7 @@ 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) { @@ -2542,17 +2508,13 @@ void filemap_map_pages(struct vm_fault *vmf, if (xa_is_value(page)) goto next; - head = compound_head(page); - 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) || diff --git a/mm/khugepaged.c b/mm/khugepaged.c index c13625c1ad5e5..7d6a1319dd42e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1363,7 +1363,7 @@ static void collapse_shmem(struct mm_struct *mm, result = SCAN_FAIL; break; } - xas_store(&xas, new_page + (index % HPAGE_PMD_NR)); + xas_store(&xas, new_page); nr_none++; continue; } @@ -1431,7 +1431,7 @@ static void collapse_shmem(struct mm_struct *mm, list_add_tail(&page->lru, &pagelist); /* Finally, replace with the new page. */ - xas_store(&xas, new_page + (index % HPAGE_PMD_NR)); + xas_store(&xas, new_page); continue; out_lru: xas_unlock_irq(&xas); diff --git a/mm/shmem.c b/mm/shmem.c index ea26d7a0342d7..c2ba84cbb0c0e 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -603,7 +603,7 @@ static int shmem_add_to_page_cache(struct page *page, if (xas_error(&xas)) goto unlock; next: - xas_store(&xas, page + i); + xas_store(&xas, page); if (++i < nr) { xas_next(&xas); goto next; diff --git a/mm/swap_state.c b/mm/swap_state.c index fd2f21e1c60ae..dcf9e466d2945 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -132,7 +132,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp) for (i = 0; i < nr; i++) { VM_BUG_ON_PAGE(xas.xa_index != idx + i, page); set_page_private(page + i, entry.val + i); - xas_store(&xas, page + i); + xas_store(&xas, page); xas_next(&xas); } address_space->nrpages += nr; -- 2.19.1
