ext4: add ability to return parsed options from parse_options

Before this patch, the function parse_options() was returning
journal_devnum and journal_ioprio variables to the caller. This patch
generalizes that interface to allow parse_options to return any parsed
options to return back to the caller. In this patch series, it gets
used to capture the value of "mb_optimize_scan=%u" mount option.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20210401172129.189766-3-harshadshirwadkar@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -2090,9 +2090,14 @@ static int ext4_set_test_dummy_encryption(struct super_block *sb,
 	return 1;
 }
 
+struct ext4_parsed_options {
+	unsigned long journal_devnum;
+	unsigned int journal_ioprio;
+};
+
 static int handle_mount_opt(struct super_block *sb, char *opt, int token,
-			    substring_t *args, unsigned long *journal_devnum,
-			    unsigned int *journal_ioprio, int is_remount)
+			    substring_t *args, struct ext4_parsed_options *parsed_opts,
+			    int is_remount)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	const struct mount_opts *m;
@@ -2249,7 +2254,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 				 "Cannot specify journal on remount");
 			return -1;
 		}
-		*journal_devnum = arg;
+		parsed_opts->journal_devnum = arg;
 	} else if (token == Opt_journal_path) {
 		char *journal_path;
 		struct inode *journal_inode;
@@ -2285,7 +2290,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 			return -1;
 		}
 
-		*journal_devnum = new_encode_dev(journal_inode->i_rdev);
+		parsed_opts->journal_devnum = new_encode_dev(journal_inode->i_rdev);
 		path_put(&path);
 		kfree(journal_path);
 	} else if (token == Opt_journal_ioprio) {
@@ -2294,7 +2299,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 				 " (must be 0-7)");
 			return -1;
 		}
-		*journal_ioprio =
+		parsed_opts->journal_ioprio =
 			IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, arg);
 	} else if (token == Opt_test_dummy_encryption) {
 		return ext4_set_test_dummy_encryption(sb, opt, &args[0],
@@ -2411,8 +2416,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 }
 
 static int parse_options(char *options, struct super_block *sb,
-			 unsigned long *journal_devnum,
-			 unsigned int *journal_ioprio,
+			 struct ext4_parsed_options *ret_opts,
 			 int is_remount)
 {
 	struct ext4_sb_info __maybe_unused *sbi = EXT4_SB(sb);
@@ -2432,8 +2436,8 @@ static int parse_options(char *options, struct super_block *sb,
 		 */
 		args[0].to = args[0].from = NULL;
 		token = match_token(p, tokens, args);
-		if (handle_mount_opt(sb, p, token, args, journal_devnum,
-				     journal_ioprio, is_remount) < 0)
+		if (handle_mount_opt(sb, p, token, args, ret_opts,
+				     is_remount) < 0)
 			return 0;
 	}
 #ifdef CONFIG_QUOTA
@@ -4015,7 +4019,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	ext4_fsblk_t sb_block = get_sb_block(&data);
 	ext4_fsblk_t logical_sb_block;
 	unsigned long offset = 0;
-	unsigned long journal_devnum = 0;
 	unsigned long def_mount_opts;
 	struct inode *root;
 	const char *descr;
@@ -4026,8 +4029,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	int needs_recovery, has_huge_files;
 	__u64 blocks_count;
 	int err = 0;
-	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 	ext4_group_t first_not_zeroed;
+	struct ext4_parsed_options parsed_opts;
+
+	/* Set defaults for the variables that will be set during parsing */
+	parsed_opts.journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
+	parsed_opts.journal_devnum = 0;
 
 	if ((data && !orig_data) || !sbi)
 		goto out_free_base;
@@ -4273,8 +4280,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 					      GFP_KERNEL);
 		if (!s_mount_opts)
 			goto failed_mount;
-		if (!parse_options(s_mount_opts, sb, &journal_devnum,
-				   &journal_ioprio, 0)) {
+		if (!parse_options(s_mount_opts, sb, &parsed_opts, 0)) {
 			ext4_msg(sb, KERN_WARNING,
 				 "failed to parse options in superblock: %s",
 				 s_mount_opts);
@@ -4282,8 +4288,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		kfree(s_mount_opts);
 	}
 	sbi->s_def_mount_opt = sbi->s_mount_opt;
-	if (!parse_options((char *) data, sb, &journal_devnum,
-			   &journal_ioprio, 0))
+	if (!parse_options((char *) data, sb, &parsed_opts, 0))
 		goto failed_mount;
 
 #ifdef CONFIG_UNICODE
@@ -4768,7 +4773,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	 * root first: it may be modified in the journal!
 	 */
 	if (!test_opt(sb, NOLOAD) && ext4_has_feature_journal(sb)) {
-		err = ext4_load_journal(sb, es, journal_devnum);
+		err = ext4_load_journal(sb, es, parsed_opts.journal_devnum);
 		if (err)
 			goto failed_mount3a;
 	} else if (test_opt(sb, NOLOAD) && !sb_rdonly(sb) &&
@@ -4868,7 +4873,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount_wq;
 	}
 
-	set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
+	set_task_ioprio(sbi->s_journal->j_task, parsed_opts.journal_ioprio);
 
 	sbi->s_journal->j_submit_inode_data_buffers =
 		ext4_journal_submit_inode_data_buffers;
@@ -5807,13 +5812,16 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	struct ext4_mount_options old_opts;
 	int enable_quota = 0;
 	ext4_group_t g;
-	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 	int err = 0;
 #ifdef CONFIG_QUOTA
 	int i, j;
 	char *to_free[EXT4_MAXQUOTAS];
 #endif
 	char *orig_data = kstrdup(data, GFP_KERNEL);
+	struct ext4_parsed_options parsed_opts;
+
+	parsed_opts.journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
+	parsed_opts.journal_devnum = 0;
 
 	if (data && !orig_data)
 		return -ENOMEM;
@@ -5844,7 +5852,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 			old_opts.s_qf_names[i] = NULL;
 #endif
 	if (sbi->s_journal && sbi->s_journal->j_task->io_context)
-		journal_ioprio = sbi->s_journal->j_task->io_context->ioprio;
+		parsed_opts.journal_ioprio =
+			sbi->s_journal->j_task->io_context->ioprio;
 
 	/*
 	 * Some options can be enabled by ext4 and/or by VFS mount flag
@@ -5854,7 +5863,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	vfs_flags = SB_LAZYTIME | SB_I_VERSION;
 	sb->s_flags = (sb->s_flags & ~vfs_flags) | (*flags & vfs_flags);
 
-	if (!parse_options(data, sb, NULL, &journal_ioprio, 1)) {
+	if (!parse_options(data, sb, &parsed_opts, 1)) {
 		err = -EINVAL;
 		goto restore_opts;
 	}
@@ -5904,7 +5913,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 
 	if (sbi->s_journal) {
 		ext4_init_journal_params(sb, sbi->s_journal);
-		set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
+		set_task_ioprio(sbi->s_journal->j_task, parsed_opts.journal_ioprio);
 	}
 
 	/* Flush outstanding errors before changing fs state */