[PATCH v5 1/2] filemap: add helper mapping_max_folio_size()

Xu Yang
2024-05-21T03:41:49Z

Add mapping_max_folio_size() to get the maximum folio size for this
pagecache mapping.

Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace")
Cc: stable@vger.kernel.org
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

---
Changes in v4:
- split the mapping_max_folio_size() from v3
- adjust mapping_max_folio_size() comment
- add Rb tag
Changes in v5:
- add fix tag and stable list
---
include/linux/pagemap.h | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c5e33e2ca48a..d43cf36bb68b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -346,6 +346,19 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
m->gfp_mask = mask;
}

+/*
+ * There are some parts of the kernel which assume that PMD entries
+ * are exactly HPAGE_PMD_ORDER. Those should be fixed, but until then,
+ * limit the maximum allocation order to PMD size. I'm not aware of any
+ * assumptions about maximum order if THP are disabled, but 8 seems like
+ * a good order (that's 1MB if you're using 4kB pages)
+ */
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#define MAX_PAGECACHE_ORDER HPAGE_PMD_ORDER
+#else
+#define MAX_PAGECACHE_ORDER 8
+#endif
+
/**
* mapping_set_large_folios() - Indicate the file supports large folios.
* @mapping: The file.
@@ -372,6 +385,14 @@ static inline bool mapping_large_folio_support(struct address_space *mapping)
test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
}

+/* Return the maximum folio size for this pagecache mapping, in bytes. */
+static inline size_t mapping_max_folio_size(struct address_space *mapping)
+{
+ if (mapping_large_folio_support(mapping))
+ return PAGE_SIZE << MAX_PAGECACHE_ORDER;
+ return PAGE_SIZE;
+}
+
static inline int filemap_nr_thps(struct address_space *mapping)
{
#ifdef CONFIG_READ_ONLY_THP_FOR_FS
@@ -530,19 +551,6 @@ static inline void *detach_page_private(struct page *page)
return folio_detach_private(page_folio(page));
}

-/*
- * There are some parts of the kernel which assume that PMD entries
- * are exactly HPAGE_PMD_ORDER. Those should be fixed, but until then,
- * limit the maximum allocation order to PMD size. I'm not aware of any
- * assumptions about maximum order if THP are disabled, but 8 seems like
- * a good order (that's 1MB if you're using 4kB pages)
- */
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define MAX_PAGECACHE_ORDER HPAGE_PMD_ORDER
-#else
-#define MAX_PAGECACHE_ORDER 8
-#endif
-
#ifdef CONFIG_NUMA
struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order);
#else
--
2.34.1