linux-ext4 - Re: [RFC/PATCH 3/3] ext4: add EXT4_IOC

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Date:   Thu, 2 Feb 2017 16:02:04 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     "Theodore Ts'o" <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [RFC/PATCH 3/3] ext4: add EXT4_IOC_GOINGDOWN ioctl

On Thu, Feb 02, 2017 at 05:59:24PM -0500, Theodore Ts'o wrote:
> This ioctl is modeled after the xfs's XFS_IOC_GOINGDOWN ioctl.  (In
> fact, it uses the same code points.)
> 
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>  fs/ext4/ext4.h  | 10 ++++++++++
>  fs/ext4/ioctl.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>  fs/ext4/super.c |  2 +-
>  3 files changed, 53 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 94064b7ce16c..eae92f1a52e1 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -679,6 +679,16 @@ struct fsxattr {
>  #define EXT4_IOC_FSGETXATTR		FS_IOC_FSGETXATTR
>  #define EXT4_IOC_FSSETXATTR		FS_IOC_FSSETXATTR
>  
> +#define EXT4_IOC_GOiNGDOWN _IOR ('X', 125, __u32)

Lowercase 'i'?

ISTR Dave asking if we could rename it IOC_SHUTDOWN way back when f2fs
was trying to implement it.

> +
> +/*
> + * Flags for going down operation
> + */
> +#define EXT4_GOING_FLAGS_DEFAULT		0x0	/* going down */
> +#define EXT4_GOING_FLAGS_LOGFLUSH		0x1	/* flush log but not data */
> +#define EXT4_GOING_FLAGS_NOLOGFLUSH		0x2	/* don't flush log nor data */
> +
> +
>  #if defined(__KERNEL__) && defined(CONFIG_COMPAT)
>  /*
>   * ioctl commands in 32 bit emulation
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index d534399cf607..6d5443cf4a47 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -442,6 +442,45 @@ static inline unsigned long ext4_xflags_to_iflags(__u32 xflags)
>  	return iflags;
>  }
>  
> +int ext4_goingdown(struct super_block *sb, unsigned long arg)
> +{
> +	struct ext4_sb_info *sbi = EXT4_SB(sb);
> +	__u32 flags;
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
> +	if (get_user(flags, (__u32 __user *)arg))
> +		return -EFAULT;
> +
> +	if (flags > EXT4_GOING_FLAGS_NOLOGFLUSH)
> +		return -EINVAL;
> +
> +	if (ext4_forced_shutdown(sbi))
> +		return 0;
> +
> +	switch (flags) {
> +	case EXT4_GOING_FLAGS_DEFAULT:
> +		freeze_bdev(sb->s_bdev);
> +		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
> +		thaw_bdev(sb->s_bdev, sb);
> +		break;
> +	case EXT4_GOING_FLAGS_LOGFLUSH:
> +		if (sbi->s_journal && !is_journal_aborted(sbi->s_journal))
> +		    (void) ext4_force_commit(sb);
> +		/* fall through */
> +	case EXT4_GOING_FLAGS_NOLOGFLUSH:
> +		if (sbi->s_journal && !is_journal_aborted(sbi->s_journal))
> +			(void) jbd2_journal_destroy(sbi->s_journal);
> +		sbi->s_journal = NULL;
> +		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +	return 0;

/me wonders if mount -o errors=shutdown follows from this? :)

(Something a little less drastic than errors=panic that stops everything
in its tracks.)

--D

> +}
> +
>  long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  {
>  	struct inode *inode = file_inode(filp);
> @@ -893,6 +932,8 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  
>  		return 0;
>  	}
> +	case EXT4_IOC_GOiNGDOWN:
> +		return ext4_goingdown(sb, arg);
>  	default:
>  		return -ENOTTY;
>  	}
> @@ -959,6 +1000,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	case EXT4_IOC_SET_ENCRYPTION_POLICY:
>  	case EXT4_IOC_GET_ENCRYPTION_PWSALT:
>  	case EXT4_IOC_GET_ENCRYPTION_POLICY:
> +	case EXT4_IOC_GOiNGDOWN:
>  		break;
>  	default:
>  		return -ENOIOCTLCMD;
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 829e4a7b59e4..8db181c4dad6 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4797,7 +4797,7 @@ static int ext4_freeze(struct super_block *sb)
>   */
>  static int ext4_unfreeze(struct super_block *sb)
>  {
> -	if (sb->s_flags & MS_RDONLY)
> +	if ((sb->s_flags & MS_RDONLY) || ext4_forced_shutdown(EXT4_SB(sb)))
>  		return 0;
>  
>  	if (EXT4_SB(sb)->s_journal) {
> -- 
> 2.11.0.rc0.7.gbe5a750
>