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filemap: prepare find and delete operations for huge pages
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For now, we would have HPAGE_PMD_NR entries in radix tree for every huge
page.  That's suboptimal and it will be changed to use Matthew's
multi-order entries later.

'add' operation is not changed, because we don't need it to implement
hugetmpfs: shmem uses its own implementation.

Link: http://lkml.kernel.org/r/1466021202-61880-25-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@kiryl @torvalds
kiryl authored and torvalds committed Jul 26, 2016
1 parent c78c66d commit 8392937
Showing 1 changed file with 122 additions and 56 deletions.
178 changes: 122 additions & 56 deletions mm/filemap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -114,14 +114,14 @@ static void page_cache_tree_delete(struct address_space *mapping,
struct page *page, void *shadow)
{
struct radix_tree_node *node;
int i, nr = PageHuge(page) ? 1 : hpage_nr_pages(page);

VM_BUG_ON(!PageLocked(page));

node = radix_tree_replace_clear_tags(&mapping->page_tree, page->index,
shadow);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageTail(page), page);
VM_BUG_ON_PAGE(nr != 1 && shadow, page);

if (shadow) {
mapping->nrexceptional++;
mapping->nrexceptional += nr;
/*
* Make sure the nrexceptional update is committed before
* the nrpages update so that final truncate racing
Expand All @@ -130,31 +130,38 @@ static void page_cache_tree_delete(struct address_space *mapping,
*/
smp_wmb();
}
mapping->nrpages--;

if (!node)
return;
mapping->nrpages -= nr;

workingset_node_pages_dec(node);
if (shadow)
workingset_node_shadows_inc(node);
else
if (__radix_tree_delete_node(&mapping->page_tree, node))
for (i = 0; i < nr; i++) {
node = radix_tree_replace_clear_tags(&mapping->page_tree,
page->index + i, shadow);
if (!node) {
VM_BUG_ON_PAGE(nr != 1, page);
return;
}

/*
* Track node that only contains shadow entries. DAX mappings contain
* no shadow entries and may contain other exceptional entries so skip
* those.
*
* Avoid acquiring the list_lru lock if already tracked. The
* list_empty() test is safe as node->private_list is
* protected by mapping->tree_lock.
*/
if (!dax_mapping(mapping) && !workingset_node_pages(node) &&
list_empty(&node->private_list)) {
node->private_data = mapping;
list_lru_add(&workingset_shadow_nodes, &node->private_list);
workingset_node_pages_dec(node);
if (shadow)
workingset_node_shadows_inc(node);
else
if (__radix_tree_delete_node(&mapping->page_tree, node))
continue;

/*
* Track node that only contains shadow entries. DAX mappings
* contain no shadow entries and may contain other exceptional
* entries so skip those.
*
* Avoid acquiring the list_lru lock if already tracked.
* The list_empty() test is safe as node->private_list is
* protected by mapping->tree_lock.
*/
if (!dax_mapping(mapping) && !workingset_node_pages(node) &&
list_empty(&node->private_list)) {
node->private_data = mapping;
list_lru_add(&workingset_shadow_nodes,
&node->private_list);
}
}
}

Expand All @@ -166,6 +173,7 @@ static void page_cache_tree_delete(struct address_space *mapping,
void __delete_from_page_cache(struct page *page, void *shadow)
{
struct address_space *mapping = page->mapping;
int nr = hpage_nr_pages(page);

trace_mm_filemap_delete_from_page_cache(page);
/*
Expand All @@ -178,6 +186,7 @@ void __delete_from_page_cache(struct page *page, void *shadow)
else
cleancache_invalidate_page(mapping, page);

VM_BUG_ON_PAGE(PageTail(page), page);
VM_BUG_ON_PAGE(page_mapped(page), page);
if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
int mapcount;
Expand Down Expand Up @@ -209,9 +218,9 @@ void __delete_from_page_cache(struct page *page, void *shadow)

/* hugetlb pages do not participate in page cache accounting. */
if (!PageHuge(page))
__dec_zone_page_state(page, NR_FILE_PAGES);
__mod_zone_page_state(page_zone(page), NR_FILE_PAGES, -nr);
if (PageSwapBacked(page))
__dec_zone_page_state(page, NR_SHMEM);
__mod_zone_page_state(page_zone(page), NR_SHMEM, -nr);

/*
* At this point page must be either written or cleaned by truncate.
Expand All @@ -235,9 +244,8 @@ void __delete_from_page_cache(struct page *page, void *shadow)
*/
void delete_from_page_cache(struct page *page)
{
struct address_space *mapping = page->mapping;
struct address_space *mapping = page_mapping(page);
unsigned long flags;

void (*freepage)(struct page *);

BUG_ON(!PageLocked(page));
Expand All @@ -250,7 +258,13 @@ void delete_from_page_cache(struct page *page)

if (freepage)
freepage(page);
put_page(page);

if (PageTransHuge(page) && !PageHuge(page)) {
page_ref_sub(page, HPAGE_PMD_NR);
VM_BUG_ON_PAGE(page_count(page) <= 0, page);
} else {
put_page(page);
}
}
EXPORT_SYMBOL(delete_from_page_cache);

Expand Down Expand Up @@ -1053,7 +1067,7 @@ EXPORT_SYMBOL(page_cache_prev_hole);
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
{
void **pagep;
struct page *page;
struct page *head, *page;

rcu_read_lock();
repeat:
Expand All @@ -1073,16 +1087,24 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
*/
goto out;
}
if (!page_cache_get_speculative(page))

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);
goto repeat;
}

/*
* Has the page moved?
* This is part of the lockless pagecache protocol. See
* include/linux/pagemap.h for details.
*/
if (unlikely(page != *pagep)) {
put_page(page);
put_page(head);
goto repeat;
}
}
Expand Down Expand Up @@ -1118,12 +1140,12 @@ struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
if (page && !radix_tree_exception(page)) {
lock_page(page);
/* Has the page been truncated? */
if (unlikely(page->mapping != mapping)) {
if (unlikely(page_mapping(page) != mapping)) {
unlock_page(page);
put_page(page);
goto repeat;
}
VM_BUG_ON_PAGE(page->index != offset, page);
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
}
return page;
}
Expand Down Expand Up @@ -1255,7 +1277,7 @@ unsigned find_get_entries(struct address_space *mapping,

rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *page;
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
Expand All @@ -1272,12 +1294,20 @@ unsigned find_get_entries(struct address_space *mapping,
*/
goto export;
}
if (!page_cache_get_speculative(page))

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);
goto repeat;
}

/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(page);
put_page(head);
goto repeat;
}
export:
Expand Down Expand Up @@ -1318,7 +1348,7 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start,

rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *page;
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
Expand All @@ -1337,12 +1367,19 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
continue;
}

if (!page_cache_get_speculative(page))
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);
goto repeat;
}

/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(page);
put_page(head);
goto repeat;
}

Expand Down Expand Up @@ -1379,7 +1416,7 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,

rcu_read_lock();
radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
struct page *page;
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
/* The hole, there no reason to continue */
Expand All @@ -1399,12 +1436,19 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
break;
}

if (!page_cache_get_speculative(page))
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);
goto repeat;
}

/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(page);
put_page(head);
goto repeat;
}

Expand All @@ -1413,7 +1457,7 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
* otherwise we can get both false positives and false
* negatives, which is just confusing to the caller.
*/
if (page->mapping == NULL || page->index != iter.index) {
if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
put_page(page);
break;
}
Expand Down Expand Up @@ -1451,7 +1495,7 @@ unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
rcu_read_lock();
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, *index, tag) {
struct page *page;
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
Expand All @@ -1476,12 +1520,19 @@ unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
continue;
}

if (!page_cache_get_speculative(page))
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);
goto repeat;
}

/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(page);
put_page(head);
goto repeat;
}

Expand Down Expand Up @@ -1525,7 +1576,7 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
rcu_read_lock();
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, start, tag) {
struct page *page;
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
Expand All @@ -1543,12 +1594,20 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
*/
goto export;
}
if (!page_cache_get_speculative(page))

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);
goto repeat;
}

/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(page);
put_page(head);
goto repeat;
}
export:
Expand Down Expand Up @@ -2137,7 +2196,7 @@ void filemap_map_pages(struct fault_env *fe,
struct address_space *mapping = file->f_mapping;
pgoff_t last_pgoff = start_pgoff;
loff_t size;
struct page *page;
struct page *head, *page;

rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
Expand All @@ -2156,12 +2215,19 @@ void filemap_map_pages(struct fault_env *fe,
goto next;
}

if (!page_cache_get_speculative(page))
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);
goto repeat;
}

/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(page);
put_page(head);
goto repeat;
}

Expand Down

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