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

9 files changed, 68 insertions, 46 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 375dee691a37..3f4c832abfed 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1261,7 +1261,6 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
 	unsigned long prev_start_byte;
 	unsigned long working_bytes = total_out - buf_start;
 	unsigned long bytes;
-	char *kaddr;
 	struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
 
 	/*
@@ -1292,9 +1291,8 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
 				PAGE_SIZE - (buf_offset % PAGE_SIZE));
 		bytes = min(bytes, working_bytes);
 
-		kaddr = kmap_atomic(bvec.bv_page);
-		memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
-		kunmap_atomic(kaddr);
+		memcpy_to_page(bvec.bv_page, bvec.bv_offset, buf + buf_offset,
+			       bytes);
 		flush_dcache_page(bvec.bv_page);
 
 		buf_offset += bytes;
diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index aa9cd11f4b78..9084a950dc09 100644
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -467,7 +467,7 @@ int lzo_decompress(struct list_head *ws, unsigned char *data_in,
 	destlen = min_t(unsigned long, destlen, PAGE_SIZE);
 	bytes = min_t(unsigned long, destlen, out_len - start_byte);
 
-	kaddr = kmap_atomic(dest_page);
+	kaddr = kmap_local_page(dest_page);
 	memcpy(kaddr, workspace->buf + start_byte, bytes);
 
 	/*
@@ -477,7 +477,7 @@ int lzo_decompress(struct list_head *ws, unsigned char *data_in,
 	 */
 	if (bytes < destlen)
 		memset(kaddr+bytes, 0, destlen-bytes);
-	kunmap_atomic(kaddr);
+	kunmap_local(kaddr);
 out:
 	return ret;
 }
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 83334df6f493..8c31357f08ed 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -249,8 +249,6 @@ int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info)
 static void cache_rbio_pages(struct btrfs_raid_bio *rbio)
 {
 	int i;
-	char *s;
-	char *d;
 	int ret;
 
 	ret = alloc_rbio_pages(rbio);
@@ -261,13 +259,7 @@ static void cache_rbio_pages(struct btrfs_raid_bio *rbio)
 		if (!rbio->bio_pages[i])
 			continue;
 
-		s = kmap(rbio->bio_pages[i]);
-		d = kmap(rbio->stripe_pages[i]);
-
-		copy_page(d, s);
-
-		kunmap(rbio->bio_pages[i]);
-		kunmap(rbio->stripe_pages[i]);
+		copy_highpage(rbio->stripe_pages[i], rbio->bio_pages[i]);
 		SetPageUptodate(rbio->stripe_pages[i]);
 	}
 	set_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index 5413578d2c32..762881b777b3 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -106,12 +106,8 @@ static int copy_inline_to_page(struct btrfs_inode *inode,
 	set_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &inode->runtime_flags);
 
 	if (comp_type == BTRFS_COMPRESS_NONE) {
-		char *map;
-
-		map = kmap(page);
-		memcpy(map, data_start, datal);
+		memcpy_to_page(page, 0, data_start, datal);
 		flush_dcache_page(page);
-		kunmap(page);
 	} else {
 		ret = btrfs_decompress(comp_type, data_start, page, 0,
 				       inline_size, datal);
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index f87878274e9f..8f323859156b 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4932,7 +4932,6 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct inode *inode;
 	struct page *page;
-	char *addr;
 	pgoff_t index = offset >> PAGE_SHIFT;
 	pgoff_t last_index;
 	unsigned pg_offset = offset_in_page(offset);
@@ -4985,10 +4984,8 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
 			}
 		}
 
-		addr = kmap(page);
-		memcpy(sctx->send_buf + sctx->send_size, addr + pg_offset,
-		       cur_len);
-		kunmap(page);
+		memcpy_from_page(sctx->send_buf + sctx->send_size, page,
+				 pg_offset, cur_len);
 		unlock_page(page);
 		put_page(page);
 		index++;
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 05615a1099db..d524acf7b3e5 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -432,9 +432,8 @@ int zlib_decompress(struct list_head *ws, unsigned char *data_in,
 			    PAGE_SIZE - (buf_offset % PAGE_SIZE));
 		bytes = min(bytes, bytes_left);
 
-		kaddr = kmap_atomic(dest_page);
-		memcpy(kaddr + pg_offset, workspace->buf + buf_offset, bytes);
-		kunmap_atomic(kaddr);
+		memcpy_to_page(dest_page, pg_offset,
+			       workspace->buf + buf_offset, bytes);
 
 		pg_offset += bytes;
 		bytes_left -= bytes;
diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 9a4871636c6c..8e9626d63976 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -688,10 +688,8 @@ int zstd_decompress(struct list_head *ws, unsigned char *data_in,
 		bytes = min_t(unsigned long, destlen - pg_offset,
 				workspace->out_buf.size - buf_offset);
 
-		kaddr = kmap_atomic(dest_page);
-		memcpy(kaddr + pg_offset, workspace->out_buf.dst + buf_offset,
-				bytes);
-		kunmap_atomic(kaddr);
+		memcpy_to_page(dest_page, pg_offset,
+			       workspace->out_buf.dst + buf_offset, bytes);
 
 		pg_offset += bytes;
 	}
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 */
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index d8ca336ff9cd..f66c62aa7154 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -464,20 +464,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
 }
 EXPORT_SYMBOL(iov_iter_init);
 
-static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
-{
-	char *from = kmap_atomic(page);
-	memcpy(to, from + offset, len);
-	kunmap_atomic(from);
-}
-
-static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
-{
-	char *to = kmap_atomic(page);
-	memcpy(to + offset, from, len);
-	kunmap_atomic(to);
-}
-
 static void memzero_page(struct page *page, size_t offset, size_t len)
 {
 	char *addr = kmap_atomic(page);