[RFC PATCH 1/4] mm: Add mempolicy support to the filemap layer

Shivank Garg
2024-11-05T16:48:06Z

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 | 40 ++++++++++++++++++++++++++++++++++++++++
mm/filemap.c | 30 +++++++++++++++++++++++++-----
2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index d9c7edb6422b..b05b696f310b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -564,15 +564,25 @@ 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(...) \
alloc_hooks(filemap_alloc_folio_noprof(__VA_ARGS__))
+#define filemap_alloc_folio_mpol(...) \
+ alloc_hooks(filemap_alloc_folio_mpol_noprof(__VA_ARGS__))

static inline struct page *__page_cache_alloc(gfp_t gfp)
{
@@ -652,6 +662,8 @@ 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 +722,34 @@ 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.
+ */
+#ifdef CONFIG_NUMA
+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);
+}
+#else
+static inline struct folio *filemap_grab_folio_mpol(struct address_space *mapping,
+ pgoff_t index, struct mempolicy *mpol)
+{
+ return filemap_grab_folio(mapping, index);
+}
+#endif /* CONFIG_NUMA */
+
/**
* 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..a870a05296c8 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(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,
--
2.34.1