[PATCH RFC 2/3] mm: Add mempolicy support to the filemap layer

[Shivank Garg <shivankg@amd.com>]

From: Shivansh Dhiman <shivansh.dhiman@amd.com>

Introduce mempolicy support to the filemap. Add filemap_grab_folio_mpol,
filemap_alloc_folio_mpol_noprof() and __filemap_get_folio_mpol() APIs that
take mempolicy struct as an argument.

The API is required by VMs using KVM guest-memfd memory backends for NUMA
mempolicy aware allocations.

Signed-off-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
---
 include/linux/pagemap.h | 30 ++++++++++++++++++++++++++++++
 mm/filemap.c            | 30 +++++++++++++++++++++++++-----
 mm/mempolicy.c          |  1 +
 3 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index d9c7edb6422b..da7e41a45588 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -564,11 +564,19 @@ static inline void *detach_page_private(struct page *page)
 
 #ifdef CONFIG_NUMA
 struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order);
+struct folio *filemap_alloc_folio_mpol_noprof(gfp_t gfp, unsigned int order,
+						struct mempolicy *mpol);
 #else
 static inline struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
 {
 	return folio_alloc_noprof(gfp, order);
 }
+static inline struct folio *filemap_alloc_folio_mpol_noprof(gfp_t gfp,
+						unsigned int order,
+						struct mempolicy *mpol)
+{
+	return filemap_alloc_folio_noprof(gfp, order);
+}
 #endif
 
 #define filemap_alloc_folio(...)				\
@@ -652,6 +660,8 @@ static inline fgf_t fgf_set_order(size_t size)
 void *filemap_get_entry(struct address_space *mapping, pgoff_t index);
 struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 		fgf_t fgp_flags, gfp_t gfp);
+struct folio *__filemap_get_folio_mpol(struct address_space *mapping,
+		pgoff_t index, fgf_t fgp_flags, gfp_t gfp, struct mempolicy *mpol);
 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
 		fgf_t fgp_flags, gfp_t gfp);
 
@@ -710,6 +720,26 @@ static inline struct folio *filemap_grab_folio(struct address_space *mapping,
 			mapping_gfp_mask(mapping));
 }
 
+/**
+ * filemap_grab_folio_mpol - grab a folio from the page cache
+ * @mapping: The address space to search
+ * @index: The page index
+ * @mpol: The mempolicy to apply
+ *
+ * Same as filemap_grab_folio(), except that it allocates the folio using
+ * given memory policy.
+ *
+ * Return: A found or created folio. ERR_PTR(-ENOMEM) if no folio is found
+ * and failed to create a folio.
+ */
+static inline struct folio *filemap_grab_folio_mpol(struct address_space *mapping,
+					pgoff_t index, struct mempolicy *mpol)
+{
+	return __filemap_get_folio_mpol(mapping, index,
+			FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
+			mapping_gfp_mask(mapping), mpol);
+}
+
 /**
  * find_get_page - find and get a page reference
  * @mapping: the address_space to search
diff --git a/mm/filemap.c b/mm/filemap.c
index d62150418b91..a94022e31974 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -990,8 +990,13 @@ int filemap_add_folio(struct address_space *mapping, struct folio *folio,
 EXPORT_SYMBOL_GPL(filemap_add_folio);
 
 #ifdef CONFIG_NUMA
-struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
+struct folio *filemap_alloc_folio_mpol_noprof(gfp_t gfp, unsigned int order,
+			struct mempolicy *mpol)
 {
+	if (mpol)
+		return folio_alloc_mpol_noprof(gfp, order, mpol,
+				NO_INTERLEAVE_INDEX, numa_node_id());
+
 	int n;
 	struct folio *folio;
 
@@ -1007,6 +1012,12 @@ struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
 	}
 	return folio_alloc_noprof(gfp, order);
 }
+EXPORT_SYMBOL(filemap_alloc_folio_mpol_noprof);
+
+struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
+{
+	return filemap_alloc_folio_mpol_noprof(gfp, order, NULL);
+}
 EXPORT_SYMBOL(filemap_alloc_folio_noprof);
 #endif
 
@@ -1861,11 +1872,12 @@ void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
 }
 
 /**
- * __filemap_get_folio - Find and get a reference to a folio.
+ * __filemap_get_folio_mpol - Find and get a reference to a folio.
  * @mapping: The address_space to search.
  * @index: The page index.
  * @fgp_flags: %FGP flags modify how the folio is returned.
  * @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
+ * @mpol: The mempolicy to apply.
  *
  * Looks up the page cache entry at @mapping & @index.
  *
@@ -1876,8 +1888,8 @@ void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
  *
  * Return: The found folio or an ERR_PTR() otherwise.
  */
-struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
-		fgf_t fgp_flags, gfp_t gfp)
+struct folio *__filemap_get_folio_mpol(struct address_space *mapping, pgoff_t index,
+		fgf_t fgp_flags, gfp_t gfp, struct mempolicy *mpol)
 {
 	struct folio *folio;
 
@@ -1947,7 +1959,7 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 			err = -ENOMEM;
 			if (order > 0)
 				alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;
-			folio = filemap_alloc_folio(alloc_gfp, order);
+			folio = filemap_alloc_folio_mpol_noprof(alloc_gfp, order, mpol);
 			if (!folio)
 				continue;
 
@@ -1978,6 +1990,14 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 		return ERR_PTR(-ENOENT);
 	return folio;
 }
+EXPORT_SYMBOL(__filemap_get_folio_mpol);
+
+struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
+		fgf_t fgp_flags, gfp_t gfp)
+{
+	return __filemap_get_folio_mpol(mapping, index,
+			fgp_flags, gfp, NULL);
+}
 EXPORT_SYMBOL(__filemap_get_folio);
 
 static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9e9450433fcc..88da732cf2be 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2281,6 +2281,7 @@ struct folio *folio_alloc_mpol_noprof(gfp_t gfp, unsigned int order,
 	return page_rmappable_folio(alloc_pages_mpol_noprof(gfp | __GFP_COMP,
 							order, pol, ilx, nid));
 }
+EXPORT_SYMBOL(folio_alloc_mpol_noprof);
 
 /**
  * vma_alloc_folio - Allocate a folio for a VMA.
-- 
2.34.1