The patch titled
Subject: mm: page cache: store only head pages in i_pages
has been added to the -mm tree. Its filename is
mm-page-cache-store-only-head-pages-in-i_pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page-cache-store-only-head-pages-in-i_pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page-cache-store-only-head-pages-in-i_pages.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: page cache: store only head pages in i_pages
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.shutemov@xxxxxxxxxxxxxxx/
Kirill and Huang Ying contributed several fixes.
Link: http://lkml.kernel.org/r/20190731210400.7419-1-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Acked-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Kirill Shutemov <kirill@xxxxxxxxxxxxx>
Reviewed-and-tested-by: Song Liu <songliubraving@xxxxxx>
Tested-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Tested-by: Qian Cai <cai@xxxxxx>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 13 +++
mm/filemap.c | 146 +++++++++++++++-----------------------
mm/huge_memory.c | 22 +++++
mm/khugepaged.c | 4 -
mm/memfd.c | 2
mm/migrate.c | 2
mm/shmem.c | 2
mm/swap_state.c | 4 -
8 files changed, 99 insertions(+), 96 deletions(-)
--- a/include/linux/pagemap.h~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/include/linux/pagemap.h
@@ -333,6 +333,19 @@ static inline struct page *grab_cache_pa
mapping_gfp_mask(mapping));
}
+static inline struct page *find_subpage(struct page *page, pgoff_t offset)
+{
+ unsigned long mask;
+
+ if (PageHuge(page))
+ return page;
+
+ VM_BUG_ON_PAGE(PageTail(page), page);
+
+ mask = (1UL << compound_order(page)) - 1;
+ return page + (offset & mask);
+}
+
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,
--- a/mm/filemap.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/filemap.c
@@ -281,11 +281,11 @@ 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 +294,44 @@ static void page_cache_delete_batch(stru
{
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 + (1UL << compound_order(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++;
}
@@ -1520,7 +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:
@@ -1535,25 +1539,19 @@ repeat:
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();
@@ -1735,7 +1733,6 @@ unsigned find_get_entries(struct address
rcu_read_lock();
xas_for_each(&xas, page, ULONG_MAX) {
- struct page *head;
if (xas_retry(&xas, page))
continue;
/*
@@ -1746,17 +1743,13 @@ unsigned find_get_entries(struct address
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;
@@ -1765,7 +1758,7 @@ export:
break;
continue;
put_page:
- put_page(head);
+ put_page(page);
retry:
xas_reset(&xas);
}
@@ -1807,33 +1800,27 @@ unsigned find_get_pages_range(struct add
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);
}
@@ -1878,7 +1865,6 @@ unsigned find_get_pages_contig(struct ad
rcu_read_lock();
for (page = xas_load(&xas); page; page = xas_next(&xas)) {
- struct page *head;
if (xas_retry(&xas, page))
continue;
/*
@@ -1888,24 +1874,19 @@ unsigned find_get_pages_contig(struct ad
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);
}
@@ -1941,7 +1922,6 @@ unsigned find_get_pages_range_tag(struct
rcu_read_lock();
xas_for_each_marked(&xas, page, end, tag) {
- struct page *head;
if (xas_retry(&xas, page))
continue;
/*
@@ -1952,26 +1932,21 @@ unsigned find_get_pages_range_tag(struct
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);
}
@@ -2652,7 +2627,7 @@ void filemap_map_pages(struct vm_fault *
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) {
@@ -2661,24 +2636,19 @@ void filemap_map_pages(struct vm_fault *
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) ||
--- a/mm/huge_memory.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/huge_memory.c
@@ -2485,6 +2485,8 @@ static void __split_huge_page(struct pag
struct page *head = compound_head(page);
pg_data_t *pgdat = page_pgdat(head);
struct lruvec *lruvec;
+ struct address_space *swap_cache = NULL;
+ unsigned long offset;
int i;
lruvec = mem_cgroup_page_lruvec(head, pgdat);
@@ -2492,6 +2494,14 @@ static void __split_huge_page(struct pag
/* complete memcg works before add pages to LRU */
mem_cgroup_split_huge_fixup(head);
+ if (PageAnon(head) && PageSwapCache(head)) {
+ swp_entry_t entry = { .val = page_private(head) };
+
+ offset = swp_offset(entry);
+ swap_cache = swap_address_space(entry);
+ xa_lock(&swap_cache->i_pages);
+ }
+
for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
__split_huge_page_tail(head, i, lruvec, list);
/* Some pages can be beyond i_size: drop them from page cache */
@@ -2501,6 +2511,12 @@ static void __split_huge_page(struct pag
if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
shmem_uncharge(head->mapping->host, 1);
put_page(head + i);
+ } else if (!PageAnon(page)) {
+ __xa_store(&head->mapping->i_pages, head[i].index,
+ head + i, 0);
+ } else if (swap_cache) {
+ __xa_store(&swap_cache->i_pages, offset + i,
+ head + i, 0);
}
}
@@ -2508,10 +2524,12 @@ static void __split_huge_page(struct pag
/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
/* Additional pin to swap cache */
- if (PageSwapCache(head))
+ if (PageSwapCache(head)) {
page_ref_add(head, 2);
- else
+ xa_unlock(&swap_cache->i_pages);
+ } else {
page_ref_inc(head);
+ }
} else {
/* Additional pin to page cache */
page_ref_add(head, 2);
--- a/mm/khugepaged.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/khugepaged.c
@@ -1378,7 +1378,7 @@ static void collapse_shmem(struct mm_str
result = SCAN_FAIL;
goto xa_locked;
}
- xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
+ xas_store(&xas, new_page);
nr_none++;
continue;
}
@@ -1454,7 +1454,7 @@ static void collapse_shmem(struct mm_str
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_unlock:
unlock_page(page);
--- a/mm/memfd.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/memfd.c
@@ -39,6 +39,7 @@ static void memfd_tag_pins(struct xa_sta
xas_for_each(xas, page, ULONG_MAX) {
if (xa_is_value(page))
continue;
+ page = find_subpage(page, xas->xa_index);
if (page_count(page) - page_mapcount(page) > 1)
xas_set_mark(xas, MEMFD_TAG_PINNED);
@@ -88,6 +89,7 @@ static int memfd_wait_for_pins(struct ad
bool clear = true;
if (xa_is_value(page))
continue;
+ page = find_subpage(page, xas.xa_index);
if (page_count(page) - page_mapcount(page) != 1) {
/*
* On the last scan, we clean up all those tags
--- a/mm/migrate.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/migrate.c
@@ -459,7 +459,7 @@ int migrate_page_move_mapping(struct add
for (i = 1; i < HPAGE_PMD_NR; i++) {
xas_next(&xas);
- xas_store(&xas, newpage + i);
+ xas_store(&xas, newpage);
}
}
--- a/mm/shmem.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/shmem.c
@@ -616,7 +616,7 @@ static int shmem_add_to_page_cache(struc
if (xas_error(&xas))
goto unlock;
next:
- xas_store(&xas, page + i);
+ xas_store(&xas, page);
if (++i < nr) {
xas_next(&xas);
goto next;
--- a/mm/swap_state.c~mm-page-cache-store-only-head-pages-in-i_pages
+++ a/mm/swap_state.c
@@ -133,7 +133,7 @@ int add_to_swap_cache(struct page *page,
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;
@@ -168,7 +168,7 @@ void __delete_from_swap_cache(struct pag
for (i = 0; i < nr; i++) {
void *entry = xas_store(&xas, NULL);
- VM_BUG_ON_PAGE(entry != page + i, entry);
+ VM_BUG_ON_PAGE(entry != page, entry);
set_page_private(page + i, 0);
xas_next(&xas);
}
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-introduce-page_size.patch
mm-introduce-page_shift.patch
mm-introduce-compound_nr.patch
mm-page-cache-store-only-head-pages-in-i_pages.patch
