btrfs: clean up cow_file_range_inline()

The start parameter to cow_file_range_inline() (and
insert_inline_extent()) is always 0, so get rid of it and simplify the
logic in those two functions. Pass btrfs_inode to insert_inline_extent()
and remove the redundant root parameter. Also document the requirements
for creating an inline extent. No functional change.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -239,12 +239,13 @@ static int btrfs_init_inode_security(struct btrfs_trans_handle *trans,
  * no overlapping inline items exist in the btree
  */
 static int insert_inline_extent(struct btrfs_trans_handle *trans,
-				struct btrfs_path *path, bool extent_inserted,
-				struct btrfs_root *root, struct inode *inode,
-				u64 start, size_t size, size_t compressed_size,
+				struct btrfs_path *path,
+				struct btrfs_inode *inode, bool extent_inserted,
+				size_t size, size_t compressed_size,
 				int compress_type,
 				struct page **compressed_pages)
 {
+	struct btrfs_root *root = inode->root;
 	struct extent_buffer *leaf;
 	struct page *page = NULL;
 	char *kaddr;
@@ -252,7 +253,6 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
 	struct btrfs_file_extent_item *ei;
 	int ret;
 	size_t cur_size = size;
-	unsigned long offset;
 
 	ASSERT((compressed_size > 0 && compressed_pages) ||
 	       (compressed_size == 0 && !compressed_pages));
@@ -264,8 +264,8 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
 		struct btrfs_key key;
 		size_t datasize;
 
-		key.objectid = btrfs_ino(BTRFS_I(inode));
-		key.offset = start;
+		key.objectid = btrfs_ino(inode);
+		key.offset = 0;
 		key.type = BTRFS_EXTENT_DATA_KEY;
 
 		datasize = btrfs_file_extent_calc_inline_size(cur_size);
@@ -303,12 +303,10 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
 		btrfs_set_file_extent_compression(leaf, ei,
 						  compress_type);
 	} else {
-		page = find_get_page(inode->i_mapping,
-				     start >> PAGE_SHIFT);
+		page = find_get_page(inode->vfs_inode.i_mapping, 0);
 		btrfs_set_file_extent_compression(leaf, ei, 0);
 		kaddr = kmap_atomic(page);
-		offset = offset_in_page(start);
-		write_extent_buffer(leaf, kaddr + offset, ptr, size);
+		write_extent_buffer(leaf, kaddr, ptr, size);
 		kunmap_atomic(kaddr);
 		put_page(page);
 	}
@@ -319,8 +317,8 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
 	 * We align size to sectorsize for inline extents just for simplicity
 	 * sake.
 	 */
-	size = ALIGN(size, root->fs_info->sectorsize);
-	ret = btrfs_inode_set_file_extent_range(BTRFS_I(inode), start, size);
+	ret = btrfs_inode_set_file_extent_range(inode, 0,
+					ALIGN(size, root->fs_info->sectorsize));
 	if (ret)
 		goto fail;
 
@@ -333,7 +331,8 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
 	 * before we unlock the pages.  Otherwise we
 	 * could end up racing with unlink.
 	 */
-	BTRFS_I(inode)->disk_i_size = inode->i_size;
+	inode->disk_i_size = i_size_read(&inode->vfs_inode);
+
 fail:
 	return ret;
 }
@@ -344,8 +343,8 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
  * does the checks required to make sure the data is small enough
  * to fit as an inline extent.
  */
-static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
-					  u64 end, size_t compressed_size,
+static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 size,
+					  size_t compressed_size,
 					  int compress_type,
 					  struct page **compressed_pages)
 {
@@ -353,26 +352,21 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 	struct btrfs_root *root = inode->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_trans_handle *trans;
-	u64 isize = i_size_read(&inode->vfs_inode);
-	u64 actual_end = min(end + 1, isize);
-	u64 inline_len = actual_end - start;
-	u64 aligned_end = ALIGN(end, fs_info->sectorsize);
-	u64 data_len = inline_len;
+	u64 data_len = (compressed_size ?: size);
 	int ret;
 	struct btrfs_path *path;
 
-	if (compressed_size)
-		data_len = compressed_size;
-
-	if (start > 0 ||
-	    actual_end > fs_info->sectorsize ||
+	/*
+	 * We can create an inline extent if it ends at or beyond the current
+	 * i_size, is no larger than a sector (decompressed), and the (possibly
+	 * compressed) data fits in a leaf and the configured maximum inline
+	 * size.
+	 */
+	if (size < i_size_read(&inode->vfs_inode) ||
+	    size > fs_info->sectorsize ||
 	    data_len > BTRFS_MAX_INLINE_DATA_SIZE(fs_info) ||
-	    (!compressed_size &&
-	    (actual_end & (fs_info->sectorsize - 1)) == 0) ||
-	    end + 1 < isize ||
-	    data_len > fs_info->max_inline) {
+	    data_len > fs_info->max_inline)
 		return 1;
-	}
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -386,30 +380,20 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 	trans->block_rsv = &inode->block_rsv;
 
 	drop_args.path = path;
-	drop_args.start = start;
-	drop_args.end = aligned_end;
+	drop_args.start = 0;
+	drop_args.end = fs_info->sectorsize;
 	drop_args.drop_cache = true;
 	drop_args.replace_extent = true;
-
-	if (compressed_size && compressed_pages)
-		drop_args.extent_item_size = btrfs_file_extent_calc_inline_size(
-		   compressed_size);
-	else
-		drop_args.extent_item_size = btrfs_file_extent_calc_inline_size(
-		    inline_len);
-
+	drop_args.extent_item_size = btrfs_file_extent_calc_inline_size(data_len);
 	ret = btrfs_drop_extents(trans, root, inode, &drop_args);
 	if (ret) {
 		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 
-	if (isize > actual_end)
-		inline_len = min_t(u64, isize, actual_end);
-	ret = insert_inline_extent(trans, path, drop_args.extent_inserted,
-				   root, &inode->vfs_inode, start,
-				   inline_len, compressed_size,
-				   compress_type, compressed_pages);
+	ret = insert_inline_extent(trans, path, inode, drop_args.extent_inserted,
+				   size, compressed_size, compress_type,
+				   compressed_pages);
 	if (ret && ret != -ENOSPC) {
 		btrfs_abort_transaction(trans, ret);
 		goto out;
@@ -418,7 +402,7 @@ static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
 		goto out;
 	}
 
-	btrfs_update_inode_bytes(inode, inline_len, drop_args.bytes_found);
+	btrfs_update_inode_bytes(inode, size, drop_args.bytes_found);
 	ret = btrfs_update_inode(trans, root, inode);
 	if (ret && ret != -ENOSPC) {
 		btrfs_abort_transaction(trans, ret);
@@ -739,12 +723,12 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
 			/* we didn't compress the entire range, try
 			 * to make an uncompressed inline extent.
 			 */
-			ret = cow_file_range_inline(BTRFS_I(inode), start, end,
+			ret = cow_file_range_inline(BTRFS_I(inode), actual_end,
 						    0, BTRFS_COMPRESS_NONE,
 						    NULL);
 		} else {
 			/* try making a compressed inline extent */
-			ret = cow_file_range_inline(BTRFS_I(inode), start, end,
+			ret = cow_file_range_inline(BTRFS_I(inode), actual_end,
 						    total_compressed,
 						    compress_type, pages);
 		}
@@ -1159,8 +1143,11 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 	 * So here we skip inline extent creation completely.
 	 */
 	if (start == 0 && fs_info->sectorsize == PAGE_SIZE) {
+		u64 actual_end = min_t(u64, i_size_read(&inode->vfs_inode),
+				       end + 1);
+
 		/* lets try to make an inline extent */
-		ret = cow_file_range_inline(inode, start, end, 0,
+		ret = cow_file_range_inline(inode, actual_end, 0,
 					    BTRFS_COMPRESS_NONE, NULL);
 		if (ret == 0) {
 			/*