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mm: page cache: store only head pages in i_pages

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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@linux.intel.com/

Kirill and Huang Ying contributed several fixes.

[willy@infradead.org: use compound_nr, squish uninit-var warning]
Link: http://lkml.kernel.org/r/20190731210400.7419-1-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Jan Kara <jack@suse.cz>
Reviewed-by: Kirill Shutemov <kirill@shutemov.name>
Reviewed-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Tested-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Tested-by: Qian Cai <cai@lca.pw>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Song Liu <songliubraving@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2019-09-23 15:34:52 -07:00 committed by Linus Torvalds
parent 875d91b11a
commit 4101196b19
8 changed files with 96 additions and 97 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/pagemap.h
View File

@ -333,6 +333,16 @@ 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)
{
if (PageHuge(page))
return page;
VM_BUG_ON_PAGE(PageTail(page), page);
return page + (offset & (compound_nr(page) - 1));
}
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,

147
mm/filemap.c
View File

@ -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 +294,43 @@ 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;
page->mapping = NULL;
/*
* Leave page->index set: truncation lookup relies
* upon it
*/
i++;
} else {
VM_BUG_ON_PAGE(page->index + HPAGE_PMD_NR - tail_pages
!= pvec->pages[i]->index, page);
tail_pages--;
/*
* 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 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++;
xas_store(&xas, NULL);
total_pages++;
}
@ -1520,7 +1523,7 @@ 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 +1538,19 @@ 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))
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();
@ -1735,7 +1732,6 @@ 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;
/*
@ -1746,17 +1742,13 @@ 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;
@ -1765,7 +1757,7 @@ unsigned find_get_entries(struct address_space *mapping,
break;
continue;
put_page:
put_page(head);
put_page(page);
retry:
xas_reset(&xas);
}
@ -1807,33 +1799,27 @@ 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);
}
@ -1878,7 +1864,6 @@ 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;
/*
@ -1888,24 +1873,19 @@ 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);
}
@ -1941,7 +1921,6 @@ 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;
/*
@ -1952,26 +1931,21 @@ 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);
}
@ -2652,7 +2626,7 @@ 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) {
@ -2661,24 +2635,19 @@ 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) ||

22
mm/huge_memory.c
View File

@ -2497,6 +2497,8 @@ static void __split_huge_page(struct page *page, struct list_head *list,
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 = 0;
int i;
lruvec = mem_cgroup_page_lruvec(head, pgdat);
@ -2504,6 +2506,14 @@ static void __split_huge_page(struct page *page, struct list_head *list,
/* 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 */
@ -2513,6 +2523,12 @@ static void __split_huge_page(struct page *page, struct list_head *list,
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);
}
}
@ -2523,10 +2539,12 @@ static void __split_huge_page(struct page *page, struct list_head *list,
/* 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);

4
mm/khugepaged.c
View File

@ -1378,7 +1378,7 @@ static void collapse_shmem(struct mm_struct *mm,
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_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_unlock:
unlock_page(page);

2
mm/memfd.c
View File

@ -39,6 +39,7 @@ static void memfd_tag_pins(struct xa_state *xas)
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 address_space *mapping)
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

2
mm/migrate.c
View File

@ -460,7 +460,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
for (i = 1; i < HPAGE_PMD_NR; i++) {
xas_next(&xas);
xas_store(&xas, newpage + i);
xas_store(&xas, newpage);
}
}

2
mm/shmem.c
View File

@ -631,7 +631,7 @@ 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;

4
mm/swap_state.c
View File

@ -133,7 +133,7 @@ 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;
@ -168,7 +168,7 @@ void __delete_from_swap_cache(struct page *page, swp_entry_t entry)
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);
}