[063/212] mm: remove irqsave/restore locking from contexts with irqs enabled

Commit Message

Andrew Morton Sept. 2, 2021, 9:53 p.m. UTC

From: Johannes Weiner <[e-mail]>
Subject: mm: remove irqsave/restore locking from contexts with irqs enabled

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since been replaced by memcg taking the page lock instead, commit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").

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Johannes Weiner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/filemap.c  |   15 ++++++---------
 mm/truncate.c |    8 +++-----
 mm/vmscan.c   |    9 ++++-----
 3 files changed, 13 insertions(+), 19 deletions(-)

Patch

--- a/mm/filemap.c~mm-remove-irqsave-restore-locking-from-contexts-with-irqs-enabled
+++ a/mm/filemap.c
@@ -258,12 +258,11 @@  static void page_cache_free_page(struct
 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
 				  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
 	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
 
 	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
 		__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);
--- a/mm/truncate.c~mm-remove-irqsave-restore-locking-from-contexts-with-irqs-enabled
+++ a/mm/truncate.c
@@ -560,21 +560,19 @@  void invalidate_mapping_pagevec(struct a
 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);
@@ -582,7 +580,7 @@  invalidate_complete_page2(struct address
 	put_page(page);	/* pagecache ref */
 	return 1;
 failed:
-	xa_unlock_irqrestore(&mapping->i_pages, flags);
+	xa_unlock_irq(&mapping->i_pages);
 	return 0;
 }
 
--- a/mm/vmscan.c~mm-remove-irqsave-restore-locking-from-contexts-with-irqs-enabled
+++ a/mm/vmscan.c
@@ -1052,14 +1052,13 @@  static pageout_t pageout(struct page *pa
 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.
 	 *
@@ -1100,7 +1099,7 @@  static int __remove_mapping(struct addre
 		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 *);
@@ -1126,7 +1125,7 @@  static int __remove_mapping(struct addre
 		    !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);
@@ -1135,7 +1134,7 @@  static int __remove_mapping(struct addre
 	return 1;
 
 cannot_free:
-	xa_unlock_irqrestore(&mapping->i_pages, flags);
+	xa_unlock_irq(&mapping->i_pages);
 	return 0;
 }