Re: [PATCH 4/4] nilfs2: add norepair mount option

[Eric Sandeen <sandeen-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Ryusuke Konishi wrote:
> This adds norepair mount option that allows users to avoid temporal
> write access to a read-only mount or snapshots during mount/recovery.
> Without this option, write access will be even performed for those
> types of mounts; the temporal write access is needed to mount root
> file system read-only after an unclean shutdown.
> 
> This option is useful for users to avoid any write access on the
> device.

For what it's worth, ext3 & ext4 just added a "norecovery" option as
an alias to "noload" which skips journal replay; xfs already has
"norecovery" - so if you wish to be consistent with ext3/ext4/xfs,
"norecovery" may be a good choice for the option?

Thanks,
-Eric

> Signed-off-by: Ryusuke Konishi <konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>
> ---
>  Documentation/filesystems/nilfs2.txt |    4 ++++
>  fs/nilfs2/super.c                    |   14 +++++++++++++-
>  fs/nilfs2/the_nilfs.c                |   20 ++++++++++++++++++--
>  include/linux/nilfs2_fs.h            |    2 ++
>  4 files changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt
> index cbd8779..77b2c25 100644
> --- a/Documentation/filesystems/nilfs2.txt
> +++ b/Documentation/filesystems/nilfs2.txt
> @@ -70,6 +70,10 @@ order=strict		Apply strict in-order semantics that preserves sequence
>  			blocks.  That means, it is guaranteed that no
>  			overtaking of events occurs in the recovered file
>  			system after a crash.
> +norepair		Disable repair action of filesystem on mount.
> +			This disables every write access on the device for
> +			read-only mount or snapshots.  This option will fail
> +			for r/w mounts on an unclean volume.
>  
>  NILFS2 usage
>  ============
> diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
> index 990ead4..d516316 100644
> --- a/fs/nilfs2/super.c
> +++ b/fs/nilfs2/super.c
> @@ -547,7 +547,7 @@ static const struct export_operations nilfs_export_ops = {
>  
>  enum {
>  	Opt_err_cont, Opt_err_panic, Opt_err_ro,
> -	Opt_nobarrier, Opt_snapshot, Opt_order,
> +	Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norepair,
>  	Opt_err,
>  };
>  
> @@ -558,6 +558,7 @@ static match_table_t tokens = {
>  	{Opt_nobarrier, "nobarrier"},
>  	{Opt_snapshot, "cp=%u"},
>  	{Opt_order, "order=%s"},
> +	{Opt_norepair, "norepair"},
>  	{Opt_err, NULL}
>  };
>  
> @@ -608,6 +609,9 @@ static int parse_options(char *options, struct super_block *sb)
>  			sbi->s_snapshot_cno = option;
>  			nilfs_set_opt(sbi, SNAPSHOT);
>  			break;
> +		case Opt_norepair:
> +			nilfs_set_opt(sbi, NOREPAIR);
> +			break;
>  		default:
>  			printk(KERN_ERR
>  			       "NILFS: Unrecognized mount option \"%s\"\n", p);
> @@ -863,6 +867,14 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
>  		goto restore_opts;
>  	}
>  
> +	if (!nilfs_valid_fs(nilfs)) {
> +		printk(KERN_WARNING "NILFS (device %s): couldn't "
> +		       "remount because the filesystem is in an "
> +		       "incomplete recovery state.\n", sb->s_id);
> +		err = -EINVAL;
> +		goto restore_opts;
> +	}
> +
>  	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
>  		goto out;
>  	if (*flags & MS_RDONLY) {
> diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
> index 890a8d3..352fed9 100644
> --- a/fs/nilfs2/the_nilfs.c
> +++ b/fs/nilfs2/the_nilfs.c
> @@ -264,8 +264,14 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
>  	int valid_fs = nilfs_valid_fs(nilfs);
>  	int err;
>  
> -	if (nilfs_loaded(nilfs))
> -		return 0;
> +	if (nilfs_loaded(nilfs)) {
> +		if (valid_fs ||
> +		    ((s_flags & MS_RDONLY) && nilfs_test_opt(sbi, NOREPAIR)))
> +			return 0;
> +		printk(KERN_ERR "NILFS: the filesystem is in an incomplete "
> +		       "recovery state.\n");
> +		return -EINVAL;
> +	}
>  
>  	if (!valid_fs) {
>  		printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
> @@ -295,6 +301,11 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
>  		goto skip_recovery;
>  
>  	if (s_flags & MS_RDONLY) {
> +		if (nilfs_test_opt(sbi, NOREPAIR)) {
> +			printk(KERN_INFO "NILFS: norepair option specified. "
> +			       "skipping roll-forward recovery\n");
> +			goto skip_recovery;
> +		}
>  		if (really_read_only) {
>  			printk(KERN_ERR "NILFS: write access "
>  			       "unavailable, cannot proceed.\n");
> @@ -302,6 +313,11 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
>  			goto failed_unload;
>  		}
>  		sbi->s_super->s_flags &= ~MS_RDONLY;
> +	} else if (nilfs_test_opt(sbi, NOREPAIR)) {
> +		printk(KERN_ERR "NILFS: recovery cancelled because norepair "
> +		       "option was specified for a read/write mount\n");
> +		err = -EINVAL;
> +		goto failed_unload;
>  	}
>  
>  	err = nilfs_recover_logical_segments(nilfs, sbi, &ri);
> diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
> index 72289d2..8376fcb 100644
> --- a/include/linux/nilfs2_fs.h
> +++ b/include/linux/nilfs2_fs.h
> @@ -151,6 +151,8 @@ struct nilfs_super_root {
>  #define NILFS_MOUNT_BARRIER		0x1000  /* Use block barriers */
>  #define NILFS_MOUNT_STRICT_ORDER	0x2000  /* Apply strict in-order
>  						   semantics also for data */
> +#define NILFS_MOUNT_NOREPAIR		0x4000  /* Disable write access during
> +						   mount-time recovery */
>  
>  
>  /**