btrfs: extract the inline extent read code into its own function

Currently we have inline extent read code behind two levels of
indentation, factor them them out into a new function,
read_inline_extent(), to make it a little easier to read.

Since we're here, also remove @extent_offset and @pg_offset arguments
from uncompress_inline() function, as it's not possible to have inline
extents at non-inline file offset.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -6865,7 +6865,6 @@ static int btrfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 
 static noinline int uncompress_inline(struct btrfs_path *path,
 				      struct page *page,
-				      size_t pg_offset, u64 extent_offset,
 				      struct btrfs_file_extent_item *item)
 {
 	int ret;
@@ -6876,7 +6875,6 @@ static noinline int uncompress_inline(struct btrfs_path *path,
 	unsigned long ptr;
 	int compress_type;
 
-	WARN_ON(pg_offset != 0);
 	compress_type = btrfs_file_extent_compression(leaf, item);
 	max_size = btrfs_file_extent_ram_bytes(leaf, item);
 	inline_size = btrfs_file_extent_inline_item_len(leaf, path->slots[0]);
@@ -6888,8 +6886,7 @@ static noinline int uncompress_inline(struct btrfs_path *path,
 	read_extent_buffer(leaf, tmp, ptr, inline_size);
 
 	max_size = min_t(unsigned long, PAGE_SIZE, max_size);
-	ret = btrfs_decompress(compress_type, tmp, page,
-			       extent_offset, inline_size, max_size);
+	ret = btrfs_decompress(compress_type, tmp, page, 0, inline_size, max_size);
 
 	/*
 	 * decompression code contains a memset to fill in any space between the end
@@ -6899,13 +6896,40 @@ static noinline int uncompress_inline(struct btrfs_path *path,
 	 * cover that region here.
 	 */
 
-	if (max_size + pg_offset < PAGE_SIZE)
-		memzero_page(page,  pg_offset + max_size,
-			     PAGE_SIZE - max_size - pg_offset);
+	if (max_size < PAGE_SIZE)
+		memzero_page(page, max_size, PAGE_SIZE - max_size);
 	kfree(tmp);
 	return ret;
 }
 
+static int read_inline_extent(struct btrfs_inode *inode, struct btrfs_path *path,
+			      struct page *page)
+{
+	struct btrfs_file_extent_item *fi;
+	void *kaddr;
+	size_t copy_size;
+
+	if (!page || PageUptodate(page))
+		return 0;
+
+	ASSERT(page_offset(page) == 0);
+
+	fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			    struct btrfs_file_extent_item);
+	if (btrfs_file_extent_compression(path->nodes[0], fi) != BTRFS_COMPRESS_NONE)
+		return uncompress_inline(path, page, fi);
+
+	copy_size = min_t(u64, PAGE_SIZE,
+			  btrfs_file_extent_ram_bytes(path->nodes[0], fi));
+	kaddr = kmap_local_page(page);
+	read_extent_buffer(path->nodes[0], kaddr,
+			   btrfs_file_extent_inline_start(fi), copy_size);
+	kunmap_local(kaddr);
+	if (copy_size < PAGE_SIZE)
+		memzero_page(page, copy_size, PAGE_SIZE - copy_size);
+	return 0;
+}
+
 /*
  * Lookup the first extent overlapping a range in a file.
  *
@@ -7064,25 +7088,15 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
 		goto insert;
 	} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
-		char *map;
-		size_t copy_size;
-
-		if (!page)
-			goto out;
-
 		/*
 		 * Inline extent can only exist at file offset 0. This is
 		 * ensured by tree-checker and inline extent creation path.
 		 * Thus all members representing file offsets should be zero.
 		 */
-		ASSERT(page_offset(page) == 0);
 		ASSERT(pg_offset == 0);
 		ASSERT(extent_start == 0);
 		ASSERT(em->start == 0);
 
-		copy_size = min_t(u64, PAGE_SIZE,
-				  btrfs_file_extent_ram_bytes(leaf, item));
-
 		/*
 		 * btrfs_extent_item_to_extent_map() should have properly
 		 * initialized em members already.
@@ -7092,24 +7106,9 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 		ASSERT(em->block_start == EXTENT_MAP_INLINE);
 		ASSERT(em->len = fs_info->sectorsize);
 
-		if (!PageUptodate(page)) {
-			if (btrfs_file_extent_compression(leaf, item) !=
-			    BTRFS_COMPRESS_NONE) {
-				ret = uncompress_inline(path, page, 0, 0, item);
-				if (ret)
-					goto out;
-			} else {
-				map = kmap_local_page(page);
-				read_extent_buffer(leaf, map,
-					btrfs_file_extent_inline_start(item),
-					copy_size);
-				if (copy_size < PAGE_SIZE)
-					memset(map + copy_size, 0,
-					       PAGE_SIZE - copy_size);
-				kunmap_local(map);
-			}
-			flush_dcache_page(page);
-		}
+		ret = read_inline_extent(inode, path, page);
+		if (ret < 0)
+			goto out;
 		goto insert;
 	}
 not_found: