The folio equivalent of memcpy_page(). It should correctly and
efficiently manage large folios:
- If one, neither or both is highmem
- If (either or both) offset+len crosses a page boundary
- If the two offsets are congruent or not
Signed-off-by: Matthew Wilcox (Oracle) <wi...@infradead.org>
---
include/linux/highmem.h | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 5c6bea81a90e..fd72f66b872a 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -404,6 +404,33 @@ static inline void memcpy_page(struct page *dst_page,
size_t dst_off,
kunmap_local(dst);
}
+static inline void memcpy_folio(struct folio *dst_folio, size_t dst_off,
+ struct folio *src_folio, size_t src_off, size_t len)
+{
+ VM_BUG_ON(dst_off + len > folio_size(dst_folio));
+ VM_BUG_ON(src_off + len > folio_size(src_folio));
+
+ do {
+ char *dst = kmap_local_folio(dst_folio, dst_off);
+ const char *src = kmap_local_folio(src_folio, src_off);
+ size_t chunk = len;
+
+ if (folio_test_highmem(dst_folio) &&
+ chunk > PAGE_SIZE - offset_in_page(dst_off))
+ chunk = PAGE_SIZE - offset_in_page(dst_off);
+ if (folio_test_highmem(src_folio) &&
+ chunk > PAGE_SIZE - offset_in_page(src_off))
+ chunk = PAGE_SIZE - offset_in_page(src_off);
+ memcpy(dst, src, chunk);
+ kunmap_local(src);
+ kunmap_local(dst);
+
+ dst_off += chunk;
+ src_off += chunk;
+ len -= chunk;
+ } while (len > 0);
+}
+
static inline void memset_page(struct page *page, size_t offset, int val,
size_t len)
{
--
2.47.2
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