highmem: add memcpy_to_folio() and memcpy_from_folio()

Patch series "More filesystem folio conversions for 6.6".

Remove the only spots in affs which actually use a struct page; there
are a few places where one is mentioned, but it's part of the interface.

The rest of this is removing the remaining calls to set_bh_page(),
and then removing the function before any new users show up.


This patch (of 7):

These are the folio equivalent of memcpy_to_page() and memcpy_from_page().

[[email protected]: use correct chunk size in memcpy()]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Konstantin Komarov <[email protected]>
Cc: Pankaj Raghav <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Tom Rix <[email protected]>
Cc: Andreas Gruenbacher <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 44 insertions, 0 deletions

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 68da30625a6c..99c474de800d 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -439,6 +439,50 @@ static inline void memzero_page(struct page *page, size_t offset, size_t len)
 	kunmap_local(addr);
 }
 
+static inline void memcpy_from_folio(char *to, struct folio *folio,
+		size_t offset, size_t len)
+{
+	VM_BUG_ON(offset + len > folio_size(folio));
+
+	do {
+		const char *from = kmap_local_folio(folio, offset);
+		size_t chunk = len;
+
+		if (folio_test_highmem(folio) &&
+		    chunk > PAGE_SIZE - offset_in_page(offset))
+			chunk = PAGE_SIZE - offset_in_page(offset);
+		memcpy(to, from, chunk);
+		kunmap_local(from);
+
+		from += chunk;
+		offset += chunk;
+		len -= chunk;
+	} while (len > 0);
+}
+
+static inline void memcpy_to_folio(struct folio *folio, size_t offset,
+		const char *from, size_t len)
+{
+	VM_BUG_ON(offset + len > folio_size(folio));
+
+	do {
+		char *to = kmap_local_folio(folio, offset);
+		size_t chunk = len;
+
+		if (folio_test_highmem(folio) &&
+		    chunk > PAGE_SIZE - offset_in_page(offset))
+			chunk = PAGE_SIZE - offset_in_page(offset);
+		memcpy(to, from, chunk);
+		kunmap_local(to);
+
+		from += chunk;
+		offset += chunk;
+		len -= chunk;
+	} while (len > 0);
+
+	flush_dcache_folio(folio);
+}
+
 /**
  * memcpy_from_file_folio - Copy some bytes from a file folio.
  * @to: The destination buffer.