Merge branch 'kmap-conversion-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull kmap conversion updates from David Sterba:
 "This contains changes regarding kmap API use and eg conversion from
  kmap_atomic to kmap_local_page.

  The API belongs to memory management but to save cross-tree
  dependency headaches we've agreed to take it through the btrfs tree
  because there are some trivial conversions possible, while the rest
  will need some time and getting the easy cases out of the way would be
  convenient.

  The changes can be grouped:

   - function exports, new helpers

   - new VM_BUG_ON for additional verification; it's been discussed if
     it should be VM_BUG_ON or BUG_ON, the former was chosen due to
     performance reasons

   - code replaced by relevant helpers"

[ This is an updated version of a request that originally came in during
  the merge window, but I asked for some updates:

    https://lore.kernel.org/lkml/cover.1614090658.git.dsterba@suse.com/

  which is why this got merge after the merge window closed.  - Linus ]

* 'kmap-conversion-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: use copy_highpage() instead of 2 kmaps()
  btrfs: use memcpy_[to|from]_page() and kmap_local_page()
  mm/highmem: Add VM_BUG_ON() to mem*_page() calls
  mm/highmem: Introduce memcpy_page(), memmove_page(), and memset_page()
  mm/highmem: Convert memcpy_[to|from]_page() to kmap_local_page()
  mm/highmem: Lift memcpy_[to|from]_page to core

1 files changed, 56 insertions, 0 deletions

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index d2c70d3772a3..44170f312ae7 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -276,4 +276,60 @@ static inline void copy_highpage(struct page *to, struct page *from)
 
 #endif
 
+static inline void memcpy_page(struct page *dst_page, size_t dst_off,
+			       struct page *src_page, size_t src_off,
+			       size_t len)
+{
+	char *dst = kmap_local_page(dst_page);
+	char *src = kmap_local_page(src_page);
+
+	VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
+	memcpy(dst + dst_off, src + src_off, len);
+	kunmap_local(src);
+	kunmap_local(dst);
+}
+
+static inline void memmove_page(struct page *dst_page, size_t dst_off,
+			       struct page *src_page, size_t src_off,
+			       size_t len)
+{
+	char *dst = kmap_local_page(dst_page);
+	char *src = kmap_local_page(src_page);
+
+	VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
+	memmove(dst + dst_off, src + src_off, len);
+	kunmap_local(src);
+	kunmap_local(dst);
+}
+
+static inline void memset_page(struct page *page, size_t offset, int val,
+			       size_t len)
+{
+	char *addr = kmap_local_page(page);
+
+	VM_BUG_ON(offset + len > PAGE_SIZE);
+	memset(addr + offset, val, len);
+	kunmap_local(addr);
+}
+
+static inline void memcpy_from_page(char *to, struct page *page,
+				    size_t offset, size_t len)
+{
+	char *from = kmap_local_page(page);
+
+	VM_BUG_ON(offset + len > PAGE_SIZE);
+	memcpy(to, from + offset, len);
+	kunmap_local(from);
+}
+
+static inline void memcpy_to_page(struct page *page, size_t offset,
+				  const char *from, size_t len)
+{
+	char *to = kmap_local_page(page);
+
+	VM_BUG_ON(offset + len > PAGE_SIZE);
+	memcpy(to + offset, from, len);
+	kunmap_local(to);
+}
+
 #endif /* _LINUX_HIGHMEM_H */