[PATCH] ext4: Add mount options in superblock

[PATCH] ext4: Add mount options in superblock

[Theodore Ts'o]

Allow mount options to be stored in the superblock.  Also add default
mount option bits for nobarrier, block_validity, discard, and nodelalloc.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/ext4.h  |    9 +++++++--
 fs/ext4/super.c |   29 +++++++++++++++++++++++------
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9ca3637..ed14e1d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1025,8 +1025,9 @@ struct ext4_super_block {
 	__le32	s_last_error_line;	/* line number where error happened */
 	__le64	s_last_error_block;	/* block involved of last error */
 	__u8	s_last_error_func[32];	/* function where the error happened */
-#define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_reserved)
-	__le32   s_reserved[128];        /* Padding to the end of the block */
+#define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_mount_opts)
+	__u8	s_mount_opts[64];
+	__le32	s_reserved[112];        /* Padding to the end of the block */
 };
 
 #define EXT4_S_ERR_LEN (EXT4_S_ERR_END - EXT4_S_ERR_START)
@@ -1341,6 +1342,10 @@ EXT4_INODE_BIT_FNS(state, state_flags)
 #define EXT4_DEFM_JMODE_DATA	0x0020
 #define EXT4_DEFM_JMODE_ORDERED	0x0040
 #define EXT4_DEFM_JMODE_WBACK	0x0060
+#define EXT4_DEFM_NOBARRIER	0x0100
+#define EXT4_DEFM_BLOCK_VALIDITY 0x0200
+#define EXT4_DEFM_DISCARD	0x0400
+#define EXT4_DEFM_NODELALLOC	0x0800
 
 /*
  * Default journal batch times
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3e3f648..3fd65eb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1003,10 +1003,10 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 		seq_puts(seq, ",journal_checksum");
 	if (test_opt(sb, I_VERSION))
 		seq_puts(seq, ",i_version");
-	if (!test_opt(sb, DELALLOC))
+	if (!test_opt(sb, DELALLOC) &&
+	    !(def_mount_opts & EXT4_DEFM_NODELALLOC))
 		seq_puts(seq, ",nodelalloc");
 
-
 	if (sbi->s_stripe)
 		seq_printf(seq, ",stripe=%lu", sbi->s_stripe);
 	/*
@@ -1030,7 +1030,7 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 	if (test_opt(sb, NO_AUTO_DA_ALLOC))
 		seq_puts(seq, ",noauto_da_alloc");
 
-	if (test_opt(sb, DISCARD))
+	if (test_opt(sb, DISCARD) && !(def_mount_opts & EXT4_DEFM_DISCARD))
 		seq_puts(seq, ",discard");
 
 	if (test_opt(sb, NOLOAD))
@@ -1039,6 +1039,10 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 	if (test_opt(sb, DIOREAD_NOLOCK))
 		seq_puts(seq, ",dioread_nolock");
 
+	if (test_opt(sb, BLOCK_VALIDITY) &&
+	    !(def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY))
+		seq_puts(seq, ",block_validity");
+
 	ext4_show_quota_options(seq, sb);
 
 	return 0;
@@ -2655,6 +2659,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		set_opt(sbi->s_mount_opt, ERRORS_CONT);
 	else
 		set_opt(sbi->s_mount_opt, ERRORS_RO);
+	if (def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY)
+		set_opt(sbi->s_mount_opt, BLOCK_VALIDITY);
+	if (def_mount_opts & EXT4_DEFM_DISCARD)
+		set_opt(sbi->s_mount_opt, DISCARD);
 
 	sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
 	sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
@@ -2662,15 +2670,23 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
 	sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
 
-	set_opt(sbi->s_mount_opt, BARRIER);
+	if ((def_mount_opts & EXT4_DEFM_NOBARRIER) == 0)
+		set_opt(sbi->s_mount_opt, BARRIER);
 
 	/*
 	 * enable delayed allocation by default
 	 * Use -o nodelalloc to turn it off
 	 */
-	if (!IS_EXT3_SB(sb))
+	if (!IS_EXT3_SB(sb) &&
+	    ((def_mount_opts & EXT4_DEFM_NODELALLOC) == 0))
 		set_opt(sbi->s_mount_opt, DELALLOC);
 
+	if (!parse_options((char *) sbi->s_es->s_mount_opts, sb,
+			   &journal_devnum, &journal_ioprio, NULL, 0)) {
+		ext4_msg(sb, KERN_WARNING,
+			 "failed to parse options in superblock: %s",
+			 sbi->s_es->s_mount_opts);
+	}
 	if (!parse_options((char *) data, sb, &journal_devnum,
 			   &journal_ioprio, NULL, 0))
 		goto failed_mount;
@@ -3141,7 +3157,8 @@ no_journal:
 		descr = "out journal";
 
 	ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
-		"Opts: %s", descr, orig_data);
+		 "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts,
+		 *sbi->s_es->s_mount_opts ? "; " : "", orig_data);
 
 	init_timer(&sbi->s_err_report);
 	sbi->s_err_report.function = print_daily_error_info;
-- 
1.7.0.4

Re: [PATCH] ext4: Add mount options in superblock

[Andreas Dilger]

On 2010-08-01, at 21:15, Theodore Ts'o wrote:
> Allow mount options to be stored in the superblock.  Also add default
> mount option bits for nobarrier, block_validity, discard, and nodelalloc.

Don't we already store mount options in s_default_mount_opts?  It seems more efficient to store them as binary flags instead of as a string.

Cheers, Andreas

Re: [PATCH] ext4: Add mount options in superblock

[Ted Ts'o]

On Tue, Aug 03, 2010 at 11:55:39AM -0600, Andreas Dilger wrote:
> On 2010-08-01, at 21:15, Theodore Ts'o wrote:
> > Allow mount options to be stored in the superblock.  Also add default
> > mount option bits for nobarrier, block_validity, discard, and nodelalloc.
> 
> Don't we already store mount options in s_default_mount_opts?  It
> seems more efficient to store them as binary flags instead of as a
> string.

For mount options that are going to be around for a long time, this
makes sense and it is indeed the preferred mechanism.  The problem is
that if we are adding and removing mount options, perhaps for internal
testing purposes using binary bitfields don't work as well, because
(a) it means we have to synchronize e2fsprogs with the kernel updates,
and (b) once used, it's hard to recycle a binary bit position since
there might be old file systems around.  So the 64 byte character
array is intended to be used as an adjunct for the binary bitfield.

      	 	     	     	   	   - Ted