[PATCH 0/3] Some more filemap folio conversions

[PATCH 0/3] Some more filemap folio conversions

[Matthew Wilcox (Oracle)]

Three more places which could easily be converted to folios.  The third
one fixes a minor bug in readahead_expand(), but it's only a performance
bug and there's few users of readahead_expand(), so I don't think it's
worth backporting.

Matthew Wilcox (Oracle) (3):
  filemap: Convert filemap_map_pmd() to take a folio
  filemap: Convert filemap_range_has_page() to use a folio
  readahead: Convert readahead_expand() to use a folio

 mm/filemap.c   | 28 +++++++++++++++-------------
 mm/readahead.c | 39 ++++++++++++++++++++++-----------------
 2 files changed, 37 insertions(+), 30 deletions(-)

-- 
2.35.1

[PATCH 1/3] filemap: Convert filemap_map_pmd() to take a folio

[Matthew Wilcox (Oracle)]

Save a few calls to compound_head().  We specify exactly which page from
the folio to use by passing in start_pgoff, which means this will work
for a folio which is larger than PMD size.  The rest of the VM isn't
prepared for that yet, but now this function is.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/filemap.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 31bf18ec6d01..b6b7efc9abc0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3259,22 +3259,24 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 }
 EXPORT_SYMBOL(filemap_fault);
 
-static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
+static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
+		pgoff_t start)
 {
 	struct mm_struct *mm = vmf->vma->vm_mm;
 
 	/* Huge page is mapped? No need to proceed. */
 	if (pmd_trans_huge(*vmf->pmd)) {
-		unlock_page(page);
-		put_page(page);
+		folio_unlock(folio);
+		folio_put(folio);
 		return true;
 	}
 
-	if (pmd_none(*vmf->pmd) && PageTransHuge(page)) {
+	if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) {
+		struct page *page = folio_file_page(folio, start);
 		vm_fault_t ret = do_set_pmd(vmf, page);
 		if (!ret) {
 			/* The page is mapped successfully, reference consumed. */
-			unlock_page(page);
+			folio_unlock(folio);
 			return true;
 		}
 	}
@@ -3284,8 +3286,8 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
 
 	/* See comment in handle_pte_fault() */
 	if (pmd_devmap_trans_unstable(vmf->pmd)) {
-		unlock_page(page);
-		put_page(page);
+		folio_unlock(folio);
+		folio_put(folio);
 		return true;
 	}
 
@@ -3368,7 +3370,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
 	if (!folio)
 		goto out;
 
-	if (filemap_map_pmd(vmf, &folio->page)) {
+	if (filemap_map_pmd(vmf, folio, start_pgoff)) {
 		ret = VM_FAULT_NOPAGE;
 		goto out;
 	}
-- 
2.35.1

[PATCH 2/3] filemap: Convert filemap_range_has_page() to use a folio

[Matthew Wilcox (Oracle)]

The folio isn't returned from this function, so this is an entirely
internal change.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/filemap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index b6b7efc9abc0..c915ded191f0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -470,7 +470,7 @@ EXPORT_SYMBOL(filemap_flush);
 bool filemap_range_has_page(struct address_space *mapping,
 			   loff_t start_byte, loff_t end_byte)
 {
-	struct page *page;
+	struct folio *folio;
 	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
 	pgoff_t max = end_byte >> PAGE_SHIFT;
 
@@ -479,11 +479,11 @@ bool filemap_range_has_page(struct address_space *mapping,
 
 	rcu_read_lock();
 	for (;;) {
-		page = xas_find(&xas, max);
-		if (xas_retry(&xas, page))
+		folio = xas_find(&xas, max);
+		if (xas_retry(&xas, folio))
 			continue;
 		/* Shadow entries don't count */
-		if (xa_is_value(page))
+		if (xa_is_value(folio))
 			continue;
 		/*
 		 * We don't need to try to pin this page; we're about to
@@ -494,7 +494,7 @@ bool filemap_range_has_page(struct address_space *mapping,
 	}
 	rcu_read_unlock();
 
-	return page != NULL;
+	return folio != NULL;
 }
 EXPORT_SYMBOL(filemap_range_has_page);
 
-- 
2.35.1

[PATCH 3/3] readahead: Convert readahead_expand() to use a folio

[Matthew Wilcox (Oracle)]

Replace the uses of page with a folio.  Also add a missing test
for workingset in the leading edge expansion.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/readahead.c | 39 ++++++++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index b10f0cf81d80..47afbca1d122 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -801,21 +801,25 @@ void readahead_expand(struct readahead_control *ractl,
 	/* Expand the leading edge downwards */
 	while (ractl->_index > new_index) {
 		unsigned long index = ractl->_index - 1;
-		struct page *page = xa_load(&mapping->i_pages, index);
+		struct folio *folio = xa_load(&mapping->i_pages, index);
 
-		if (page && !xa_is_value(page))
-			return; /* Page apparently present */
+		if (folio && !xa_is_value(folio))
+			return; /* Folio apparently present */
 
-		page = __page_cache_alloc(gfp_mask);
-		if (!page)
+		folio = filemap_alloc_folio(gfp_mask, 0);
+		if (!folio)
 			return;
-		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
-			put_page(page);
+		if (filemap_add_folio(mapping, folio, index, gfp_mask) < 0) {
+			folio_put(folio);
 			return;
 		}
-
+		if (unlikely(folio_test_workingset(folio)) &&
+				!ractl->_workingset) {
+			ractl->_workingset = true;
+			psi_memstall_enter(&ractl->_pflags);
+		}
 		ractl->_nr_pages++;
-		ractl->_index = page->index;
+		ractl->_index = folio->index;
 	}
 
 	new_len += new_start - readahead_pos(ractl);
@@ -824,19 +828,20 @@ void readahead_expand(struct readahead_control *ractl,
 	/* Expand the trailing edge upwards */
 	while (ractl->_nr_pages < new_nr_pages) {
 		unsigned long index = ractl->_index + ractl->_nr_pages;
-		struct page *page = xa_load(&mapping->i_pages, index);
+		struct folio *folio = xa_load(&mapping->i_pages, index);
 
-		if (page && !xa_is_value(page))
-			return; /* Page apparently present */
+		if (folio && !xa_is_value(folio))
+			return; /* Folio apparently present */
 
-		page = __page_cache_alloc(gfp_mask);
-		if (!page)
+		folio = filemap_alloc_folio(gfp_mask, 0);
+		if (!folio)
 			return;
-		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
-			put_page(page);
+		if (filemap_add_folio(mapping, folio, index, gfp_mask) < 0) {
+			folio_put(folio);
 			return;
 		}
-		if (unlikely(PageWorkingset(page)) && !ractl->_workingset) {
+		if (unlikely(folio_test_workingset(folio)) &&
+				!ractl->_workingset) {
 			ractl->_workingset = true;
 			psi_memstall_enter(&ractl->_pflags);
 		}
-- 
2.35.1

Re: [PATCH 0/3] Some more filemap folio conversions

[William Kucharski]

These all look good to me.

Reviewed-by: William Kucharski <william.kucharski@oracle.com>


> On Jan 16, 2023, at 12:39 PM, Matthew Wilcox (Oracle) <willy@infradead.org> wrote:
> 
> Three more places which could easily be converted to folios.  The third
> one fixes a minor bug in readahead_expand(), but it's only a performance
> bug and there's few users of readahead_expand(), so I don't think it's
> worth backporting.
> 
> Matthew Wilcox (Oracle) (3):
>  filemap: Convert filemap_map_pmd() to take a folio
>  filemap: Convert filemap_range_has_page() to use a folio
>  readahead: Convert readahead_expand() to use a folio
> 
> mm/filemap.c   | 28 +++++++++++++++-------------
> mm/readahead.c | 39 ++++++++++++++++++++++-----------------
> 2 files changed, 37 insertions(+), 30 deletions(-)
> 
> -- 
> 2.35.1
> 
>