ANDROID: Incremental fs: Fix crash polling 0 size read_log

When read log is 0 sized, we still need to init the wait queue to avoid
kernel panics if someone does decide to poll on the read log.

Test: Added test for this condition, incfs_test crashes
	With fix, incfs_test doesn't crash
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Bug: 152909243
Change-Id: Ic3250523bb7ddb1839f8e95852c17103e5ffb782
Git-commit: 759d52ee9e
Git-repo: https://android.googlesource.com/kernel/common/
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>

fs/incfs/data_mgmt.c

@@ -34,13 +34,13 @@ struct mount_info *incfs_alloc_mount_info(struct super_block *sb,
 	mutex_init(&mi->mi_dir_struct_mutex);
 	mutex_init(&mi->mi_pending_reads_mutex);
 	init_waitqueue_head(&mi->mi_pending_reads_notif_wq);
+	init_waitqueue_head(&mi->mi_log.ml_notif_wq);
 	INIT_LIST_HEAD(&mi->mi_reads_list_head);
 
 	if (options->read_log_pages != 0) {
 		size_t buf_size = PAGE_SIZE * options->read_log_pages;
 
 		spin_lock_init(&mi->mi_log.rl_writer_lock);
-		init_waitqueue_head(&mi->mi_log.ml_notif_wq);
 
 		mi->mi_log.rl_size = buf_size / sizeof(*mi->mi_log.rl_ring_buf);
 		mi->mi_log.rl_ring_buf = kzalloc(buf_size, GFP_NOFS);

tools/testing/selftests/filesystems/incfs/incfs_test.c

@@ -1930,7 +1930,8 @@ static int hash_tree_test(char *mount_dir)
 	return TEST_FAILURE;
 }
 
-static int validate_logs(char *mount_dir, int log_fd, struct test_file *file)
+static int validate_logs(char *mount_dir, int log_fd, struct test_file *file,
+			 bool no_rlog)
 {
 	uint8_t data[INCFS_DATA_FILE_BLOCK_SIZE];
 	struct incfs_pending_read_info prs[100] = {};
@@ -1957,7 +1958,19 @@ static int validate_logs(char *mount_dir, int log_fd, struct test_file *file)
 			goto failure;
 	}
 
-	read_count = wait_for_pending_reads(log_fd, 0, prs, prs_size);
+	read_count =
+		wait_for_pending_reads(log_fd, no_rlog ? 10 : 0, prs, prs_size);
+	if (no_rlog) {
+		if (read_count == 0)
+			goto success;
+		if (read_count < 0)
+			ksft_print_msg("Error reading logged reads %s.\n",
+				       strerror(-read_count));
+		else
+			ksft_print_msg("Somehow read empty logs.\n");
+		goto failure;
+	}
+
 	if (read_count < 0) {
 		ksft_print_msg("Error reading logged reads %s.\n",
 			       strerror(-read_count));
@@ -2001,6 +2014,8 @@ static int validate_logs(char *mount_dir, int log_fd, struct test_file *file)
 			goto failure;
 		}
 	}
+
+success:
 	close(fd);
 	return TEST_SUCCESS;
 
@@ -2029,7 +2044,7 @@ static int read_log_test(char *mount_dir)
 		goto failure;
 
 	log_fd = open_log_file(mount_dir);
-	if (cmd_fd < 0)
+	if (log_fd < 0)
 		ksft_print_msg("Can't open log file.\n");
 
 	/* Write data. */
@@ -2048,7 +2063,7 @@ static int read_log_test(char *mount_dir)
 	for (i = 0; i < file_num; i++) {
 		struct test_file *file = &test.files[i];
 
-		if (validate_logs(mount_dir, log_fd, file))
+		if (validate_logs(mount_dir, log_fd, file, false))
 			goto failure;
 	}
 
@@ -2069,19 +2084,45 @@ static int read_log_test(char *mount_dir)
 		goto failure;
 
 	log_fd = open_log_file(mount_dir);
-	if (cmd_fd < 0)
+	if (log_fd < 0)
 		ksft_print_msg("Can't open log file.\n");
 
 	/* Validate data again */
 	for (i = 0; i < file_num; i++) {
 		struct test_file *file = &test.files[i];
 
-		if (validate_logs(mount_dir, log_fd, file))
+		if (validate_logs(mount_dir, log_fd, file, false))
+			goto failure;
+	}
+
+	/*
+	 * Unmount and mount again with no read log to make sure poll
+	 * doesn't crash
+	 */
+	close(cmd_fd);
+	close(log_fd);
+	if (umount(mount_dir) != 0) {
+		print_error("Can't unmout FS");
+		goto failure;
+	}
+
+	if (mount_fs_opt(mount_dir, backing_dir, "readahead=0,rlog_pages=0") !=
+	    0)
+		goto failure;
+
+	log_fd = open_log_file(mount_dir);
+	if (log_fd < 0)
+		ksft_print_msg("Can't open log file.\n");
+
+	/* Validate data again - note should fail this time */
+	for (i = 0; i < file_num; i++) {
+		struct test_file *file = &test.files[i];
+
+		if (validate_logs(mount_dir, log_fd, file, true))
 			goto failure;
 	}
 
 	/* Final unmount */
-	close(cmd_fd);
 	close(log_fd);
 	free(backing_dir);
 	if (umount(mount_dir) != 0) {