ANDROID: Incremental fs: get_filled_blocks: better index_out

When returning incomplete results index_out has to be usable to
call the function again and resume from the same location. This
means that if the output buffer was too small the function needs
to check for that when encountering the _beginning_ of a next
output range, not the end of it. Otherwise resuming from the
end of the range that didn't fit into the buffer would cause
the call to never return that range

+ Make the backing file header flags update thread safe

Bug: 152691988
Test: libincfs-test, incfs_test passes
Signed-off-by: Yurii Zubrytskyi <zyy@google.com>
Change-Id: I351156beba0b74e1942a39117279d3fcdb5e0c78
Signed-off-by: Paul Lawrence <paullawrence@google.com>

fs/incfs/data_mgmt.c

@@ -372,11 +372,19 @@ static int get_data_file_block(struct data_file *df, int index,
 	return 0;
 }
 
+static int check_room_for_one_range(u32 size, u32 size_out)
+{
+	if (size_out + sizeof(struct incfs_filled_range) > size)
+		return -ERANGE;
+	return 0;
+}
+
 static int copy_one_range(struct incfs_filled_range *range, void __user *buffer,
 			  u32 size, u32 *size_out)
 {
-	if (*size_out + sizeof(*range) > size)
-		return -ERANGE;
+	int error = check_room_for_one_range(size, *size_out);
+	if (error)
+		return error;
 
 	if (copy_to_user(((char *)buffer) + *size_out, range, sizeof(*range)))
 		return -EFAULT;
@@ -385,6 +393,34 @@ static int copy_one_range(struct incfs_filled_range *range, void __user *buffer,
 	return 0;
 }
 
+static int update_file_header_flags(struct data_file *df, u32 bits_to_reset,
+				    u32 bits_to_set)
+{
+	int result;
+	u32 new_flags;
+	struct backing_file_context *bfc;
+
+	if (!df)
+		return -EFAULT;
+	bfc = df->df_backing_file_context;
+	if (!bfc)
+		return -EFAULT;
+
+	result = mutex_lock_interruptible(&bfc->bc_mutex);
+	if (result)
+		return result;
+
+	new_flags = (df->df_header_flags & ~bits_to_reset) | bits_to_set;
+	if (new_flags != df->df_header_flags) {
+		df->df_header_flags = new_flags;
+		result = incfs_write_file_header_flags(bfc, new_flags);
+	}
+
+	mutex_unlock(&bfc->bc_mutex);
+
+	return result;
+}
+
 int incfs_get_filled_blocks(struct data_file *df,
 			    struct incfs_get_filled_blocks_args *arg)
 {
@@ -408,14 +444,22 @@ int incfs_get_filled_blocks(struct data_file *df,
 			arg->index_out = arg->start_index;
 			return 0;
 		}
+		arg->index_out = arg->start_index;
+
+		error = check_room_for_one_range(size, *size_out);
+		if (error)
+			return error;
 
 		range = (struct incfs_filled_range){
 			.begin = arg->start_index,
 			.end = end_index,
 		};
 
+		error = copy_one_range(&range, buffer, size, size_out);
+		if (error)
+			return error;
 		arg->index_out = end_index;
-		return copy_one_range(&range, buffer, size, size_out);
+		return 0;
 	}
 
 	for (arg->index_out = arg->start_index; arg->index_out < end_index;
@@ -430,13 +474,20 @@ int incfs_get_filled_blocks(struct data_file *df,
 			continue;
 
 		if (!in_range) {
+			error = check_room_for_one_range(size, *size_out);
+			if (error)
+				break;
 			in_range = true;
 			range.begin = arg->index_out;
 		} else {
 			range.end = arg->index_out;
 			error = copy_one_range(&range, buffer, size, size_out);
-			if (error)
+			if (error) {
+				/* there will be another try out of the loop,
+				 * it will reset the index_out if it fails too
+				 */
 				break;
+			}
 			in_range = false;
 		}
 	}
@@ -444,17 +495,15 @@ int incfs_get_filled_blocks(struct data_file *df,
 	if (in_range) {
 		range.end = arg->index_out;
 		error = copy_one_range(&range, buffer, size, size_out);
+		if (error)
+			arg->index_out = range.begin;
 	}
 
 	if (!error && in_range && arg->start_index == 0 &&
 	    end_index == df->df_total_block_count &&
 	    *size_out == sizeof(struct incfs_filled_range)) {
-		int result;
-
-		df->df_header_flags |= INCFS_FILE_COMPLETE;
-		result = incfs_update_file_header_flags(
-			df->df_backing_file_context, df->df_header_flags);
-
+		int result =
+			update_file_header_flags(df, 0, INCFS_FILE_COMPLETE);
 		/* Log failure only, since it's just a failed optimization */
 		pr_debug("Marked file full with result %d", result);
 	}

fs/incfs/format.c

@@ -215,7 +215,7 @@ static int append_md_to_backing_file(struct backing_file_context *bfc,
 	return result;
 }
 
-int incfs_update_file_header_flags(struct backing_file_context *bfc, u32 flags)
+int incfs_write_file_header_flags(struct backing_file_context *bfc, u32 flags)
 {
 	if (!bfc)
 		return -EFAULT;

fs/incfs/format.h

@@ -311,7 +311,7 @@ int incfs_write_file_attr_to_backing_file(struct backing_file_context *bfc,
 int incfs_write_signature_to_backing_file(struct backing_file_context *bfc,
 					  struct mem_range sig, u32 tree_size);
 
-int incfs_update_file_header_flags(struct backing_file_context *bfc, u32 flags);
+int incfs_write_file_header_flags(struct backing_file_context *bfc, u32 flags);
 
 int incfs_make_empty_backing_file(struct backing_file_context *bfc,
 				  incfs_uuid_t *uuid, u64 file_size);