diff mbox series

[Concept,20/21] ext4l: Add a CONFIG_EXT4_MOUNT_OPTS option

Message ID 20260108185149.1995917-21-sjg@u-boot.org
State New
Headers
Series ext4l: Add Kconfig options to reduce binary size (part P) |

Commit Message

Simon Glass Jan. 8, 2026, 6:51 p.m. UTC 
  From: Simon Glass <simon.glass@canonical.com>

The ext4 mount-option-parsing infrastructure includes specification
tables (ext4_param_specs, ext4_mount_opts) and related functions that
add about 23K of rodata. For U-Boot's typical use case of mounting
with default options, this parsing is unnecessary. Even if the options
are needed in the future, it might be good enough to use the flags
direcrly.

Add a CONFIG_EXT4_MOUNT_OPTS option that, when disabled:
- Stubs out ext4_parse_param() to accept any options silently
- Removes the parameter-specification tables
- Stubs ext4_show_options() and related functions

This reduces code size by about 3.5K

Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>
---

 fs/ext4l/Kconfig | 14 ++++++++++
 fs/ext4l/super.c | 69 +++++++++++++++++++++++++++++++++---------------
 2 files changed, 61 insertions(+), 22 deletions(-)
diff mbox series

Patch

diff --git a/fs/ext4l/Kconfig b/fs/ext4l/Kconfig
index fcd5953b6dd..4d0f6d95926 100644
--- a/fs/ext4l/Kconfig
+++ b/fs/ext4l/Kconfig
@@ -49,6 +49,20 @@  config EXT4L_PRINT
 	  Messages are always recorded and can be retrieved programmatically;
 	  this option controls whether they are also printed.
 
+config EXT4_MOUNT_OPTS
+	bool "Enable mount option parsing"
+	depends on FS_EXT4L
+	help
+	  Enable parsing of ext4 mount options (e.g., "data=ordered",
+	  "barrier=1"). This requires the mount option specification
+	  tables which add about 2KB of rodata.
+
+	  When disabled, ext4 uses fixed default options suitable for
+	  read-only operation. This saves space but prevents customising
+	  mount behaviour.
+
+	  If unsure, say N.
+
 config EXT4_RESIZE
 	bool "Enable ext4 online resize support"
 	depends on FS_EXT4L
diff --git a/fs/ext4l/super.c b/fs/ext4l/super.c
index 98785935f19..9d8fee07907 100644
--- a/fs/ext4l/super.c
+++ b/fs/ext4l/super.c
@@ -61,7 +61,12 @@  static int ext4_reconfigure(struct fs_context *fc);
 static void ext4_fc_free(struct fs_context *fc);
 static int ext4_init_fs_context(struct fs_context *fc);
 static void ext4_kill_sb(struct super_block *sb);
+#ifdef CONFIG_EXT4_MOUNT_OPTS
 static const struct fs_parameter_spec ext4_param_specs[];
+#define EXT4_PARAM_SPECS ext4_param_specs
+#else
+#define EXT4_PARAM_SPECS NULL
+#endif
 
 /*
  * Lock ordering
@@ -102,7 +107,7 @@  static struct file_system_type ext2_fs_type = {
 	.owner			= THIS_MODULE,
 	.name			= "ext2",
 	.init_fs_context	= ext4_init_fs_context,
-	.parameters		= ext4_param_specs,
+	.parameters		= EXT4_PARAM_SPECS,
 	.kill_sb		= ext4_kill_sb,
 	.fs_flags		= FS_REQUIRES_DEV,
 };
@@ -118,7 +123,7 @@  static struct file_system_type ext3_fs_type = {
 	.owner			= THIS_MODULE,
 	.name			= "ext3",
 	.init_fs_context	= ext4_init_fs_context,
-	.parameters		= ext4_param_specs,
+	.parameters		= EXT4_PARAM_SPECS,
 	.kill_sb		= ext4_kill_sb,
 	.fs_flags		= FS_REQUIRES_DEV,
 };
@@ -1663,6 +1668,24 @@  enum {
 #endif
 };
 
+#define MOPT_SET	0x0001
+#define MOPT_CLEAR	0x0002
+#define MOPT_NOSUPPORT	0x0004
+#define MOPT_EXPLICIT	0x0008
+#ifdef CONFIG_QUOTA
+#define MOPT_Q		0
+#define MOPT_QFMT	0x0010
+#else
+#define MOPT_Q		MOPT_NOSUPPORT
+#define MOPT_QFMT	MOPT_NOSUPPORT
+#endif
+#define MOPT_NO_EXT2	0x0020
+#define MOPT_NO_EXT3	0x0040
+#define MOPT_EXT4_ONLY	(MOPT_NO_EXT2 | MOPT_NO_EXT3)
+#define MOPT_SKIP	0x0080
+#define	MOPT_2		0x0100
+
+#ifdef CONFIG_EXT4_MOUNT_OPTS
 static const struct constant_table ext4_param_errors[] = {
 	{"continue",	EXT4_MOUNT_ERRORS_CONT},
 	{"panic",	EXT4_MOUNT_ERRORS_PANIC},
@@ -1803,24 +1826,6 @@  static const struct fs_parameter_spec ext4_param_specs[] = {
 	{}
 };
 
-
-#define MOPT_SET	0x0001
-#define MOPT_CLEAR	0x0002
-#define MOPT_NOSUPPORT	0x0004
-#define MOPT_EXPLICIT	0x0008
-#ifdef CONFIG_QUOTA
-#define MOPT_Q		0
-#define MOPT_QFMT	0x0010
-#else
-#define MOPT_Q		MOPT_NOSUPPORT
-#define MOPT_QFMT	MOPT_NOSUPPORT
-#endif
-#define MOPT_NO_EXT2	0x0020
-#define MOPT_NO_EXT3	0x0040
-#define MOPT_EXT4_ONLY	(MOPT_NO_EXT2 | MOPT_NO_EXT3)
-#define MOPT_SKIP	0x0080
-#define	MOPT_2		0x0100
-
 static const struct mount_opts {
 	int	token;
 	int	mount_opt;
@@ -1895,6 +1900,7 @@  static const struct mount_opts {
 	{Opt_abort, EXT4_MOUNT2_ABORT, MOPT_SET | MOPT_2},
 	{Opt_err, 0, 0}
 };
+#endif /* CONFIG_EXT4_MOUNT_OPTS */
 
 #if IS_ENABLED(CONFIG_UNICODE)
 static const struct ext4_sb_encodings {
@@ -2084,6 +2090,7 @@  EXT4_SET_CTX(mount_opt2);
 EXT4_CLEAR_CTX(mount_opt2);
 EXT4_TEST_CTX(mount_opt2);
 
+#ifdef CONFIG_EXT4_MOUNT_OPTS
 static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct ext4_fs_context *ctx = fc->fs_private;
@@ -2377,6 +2384,13 @@  static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
 
 	return 0;
 }
+#else
+/* Stub when mount option parsing is disabled - use defaults */
+static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	return 0;
+}
+#endif /* CONFIG_EXT4_MOUNT_OPTS */
 
 static int parse_options(struct fs_context *fc, char *options)
 {
@@ -2862,6 +2876,7 @@  static inline void ext4_show_quota_options(struct seq_file *seq,
 #endif
 }
 
+#ifdef CONFIG_EXT4_MOUNT_OPTS
 static const char *token2str(int token)
 {
 	const struct fs_parameter_spec *spec;
@@ -2871,7 +2886,6 @@  static const char *token2str(int token)
 			break;
 	return spec->name;
 }
-
 /*
  * Show an option if
  *  - it's set to a non-default value OR
@@ -3018,6 +3032,17 @@  int ext4_seq_options_show(struct seq_file *seq, void *offset)
 	seq_putc(seq, '\n');
 	return rc;
 }
+#else
+static int ext4_show_options(struct seq_file *seq, struct dentry *root)
+{
+	return 0;
+}
+
+int ext4_seq_options_show(struct seq_file *seq, void *offset)
+{
+	return 0;
+}
+#endif /* CONFIG_EXT4_MOUNT_OPTS */
 
 static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 			    int read_only)
@@ -7397,7 +7422,7 @@  static struct file_system_type ext4_fs_type = {
 	.owner			= THIS_MODULE,
 	.name			= "ext4",
 	.init_fs_context	= ext4_init_fs_context,
-	.parameters		= ext4_param_specs,
+	.parameters		= EXT4_PARAM_SPECS,
 	.kill_sb		= ext4_kill_sb,
 	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME,
 };