[PATCH 1/4] mm: remove irqsave/restore locking from contexts with irqs enabled

Johannes Weiner
2021-06-14T21:20:21Z

The page cache deletion paths all have interrupts enabled, so no need
to use irqsafe/irqrestore locking variants.

They used to have irqs disabled by the memcg lock added in commit
c4843a7593a9 ("memcg: add per cgroup dirty page accounting"), but that
has since been replaced by memcg taking the page lock instead, commit
0a31bc97c80c ("mm: memcontrol: rewrite uncharge AP").

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
mm/filemap.c | 15 ++++++---------
mm/truncate.c | 8 +++-----
mm/vmscan.c | 9 ++++-----
3 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index ba1068a1837f..819d2589abef 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -258,12 +258,11 @@ static void page_cache_free_page(struct address_space *mapping,
void delete_from_page_cache(struct page *page)
{
struct address_space *mapping = page_mapping(page);
- unsigned long flags;

BUG_ON(!PageLocked(page));
- xa_lock_irqsave(&mapping->i_pages, flags);
+ xa_lock_irq(&mapping->i_pages);
__delete_from_page_cache(page, NULL);
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);

page_cache_free_page(mapping, page);
}
@@ -335,19 +334,18 @@ void delete_from_page_cache_batch(struct address_space *mapping,
struct pagevec *pvec)
{
int i;
- unsigned long flags;

if (!pagevec_count(pvec))
return;

- xa_lock_irqsave(&mapping->i_pages, flags);
+ xa_lock_irq(&mapping->i_pages);
for (i = 0; i < pagevec_count(pvec); i++) {
trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);

unaccount_page_cache_page(mapping, pvec->pages[i]);
}
page_cache_delete_batch(mapping, pvec);
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);

for (i = 0; i < pagevec_count(pvec); i++)
page_cache_free_page(mapping, pvec->pages[i]);
@@ -821,7 +819,6 @@ void replace_page_cache_page(struct page *old, struct page *new)
void (*freepage)(struct page *) = mapping->a_ops->freepage;
pgoff_t offset = old->index;
XA_STATE(xas, &mapping->i_pages, offset);
- unsigned long flags;

VM_BUG_ON_PAGE(!PageLocked(old), old);
VM_BUG_ON_PAGE(!PageLocked(new), new);
@@ -833,7 +830,7 @@ void replace_page_cache_page(struct page *old, struct page *new)

mem_cgroup_migrate(old, new);

- xas_lock_irqsave(&xas, flags);
+ xas_lock_irq(&xas);
xas_store(&xas, new);

old->mapping = NULL;
@@ -846,7 +843,7 @@ void replace_page_cache_page(struct page *old, struct page *new)
__dec_lruvec_page_state(old, NR_SHMEM);
if (PageSwapBacked(new))
__inc_lruvec_page_state(new, NR_SHMEM);
- xas_unlock_irqrestore(&xas, flags);
+ xas_unlock_irq(&xas);
if (freepage)
freepage(old);
put_page(old);
diff --git a/mm/truncate.c b/mm/truncate.c
index 57a618c4a0d6..b92b86222625 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -563,21 +563,19 @@ void invalidate_mapping_pagevec(struct address_space *mapping,
static int
invalidate_complete_page2(struct address_space *mapping, struct page *page)
{
- unsigned long flags;
-
if (page->mapping != mapping)
return 0;

if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
return 0;

- xa_lock_irqsave(&mapping->i_pages, flags);
+ xa_lock_irq(&mapping->i_pages);
if (PageDirty(page))
goto failed;

BUG_ON(page_has_private(page));
__delete_from_page_cache(page, NULL);
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);

if (mapping->a_ops->freepage)
mapping->a_ops->freepage(page);
@@ -585,7 +583,7 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page)
put_page(page); /* pagecache ref */
return 1;
failed:
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);
return 0;
}

diff --git a/mm/vmscan.c b/mm/vmscan.c
index eb314525c889..cc5d7cd75935 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1049,14 +1049,13 @@ static pageout_t pageout(struct page *page, struct address_space *mapping)
static int __remove_mapping(struct address_space *mapping, struct page *page,
bool reclaimed, struct mem_cgroup *target_memcg)
{
- unsigned long flags;
int refcount;
void *shadow = NULL;

BUG_ON(!PageLocked(page));
BUG_ON(mapping != page_mapping(page));

- xa_lock_irqsave(&mapping->i_pages, flags);
+ xa_lock_irq(&mapping->i_pages);
/*
* The non racy check for a busy page.
*
@@ -1097,7 +1096,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
if (reclaimed && !mapping_exiting(mapping))
shadow = workingset_eviction(page, target_memcg);
__delete_from_swap_cache(page, swap, shadow);
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);
put_swap_page(page, swap);
} else {
void (*freepage)(struct page *);
@@ -1123,7 +1122,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
!mapping_exiting(mapping) && !dax_mapping(mapping))
shadow = workingset_eviction(page, target_memcg);
__delete_from_page_cache(page, shadow);
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);

if (freepage != NULL)
freepage(page);
@@ -1132,7 +1131,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
return 1;

cannot_free:
- xa_unlock_irqrestore(&mapping->i_pages, flags);
+ xa_unlock_irq(&mapping->i_pages);
return 0;
}

--
2.32.0