linux-ext4 - Re: [PATCH, RFC V3] ext3: add ioctl to force 32-bit hashes from indexed dirs

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Date:	Wed, 3 Apr 2013 14:54:19 +0200
From:	Jan Kara <jack@...e.cz>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	Anand Avati <avati@...hat.com>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH, RFC V3] ext3: add ioctl to force 32-bit hashes from
 indexed dirs

On Mon 01-04-13 10:33:41, Eric Sandeen wrote:
> This adds a new ioctl, EXT3_IOC_32BITHASH, which allows a
> userspace application to request 32-bit rather than 64-bit
> hashes from readdir on an indexed / dx / htree directory.
> 
> Gluster had been relying on the top bits of the d_off being
> free; there are some reports that filling all 64 bits breaks
> Samba as well.  The infrastructure to return 32-bit hashes
> already exists; NFS can turn it on, and it's turned on for
> 32-bit processes as well.  So it's just a matter of flipping
> on the f_mode flag before readdir starts.
> 
> Care needs to be taken that we don't change the FMODE flag
> after readdir has been started, so we make sure that
> filp->private_data has not yet been set before we set the flag.
> (Thanks Zach!).
  OK, I'm happy with this patch. So if Samba people confirm they are really
going to use it, I'll merge the patch.

								Honza

> Pre-submission-fixes-by: Zach Brown <zab@...hat.com>
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
> ---
> 
> V2:
> fix "readir" typo
> rename goto target to *_out like others
> remove parameter; we can't really ever turn this back off once it's used.
> closing and reopening is the only way to get back to 64 bit hashes.
> 
> V3:
> return -ENOTDIR if the target is not a directory
> 
> 
> 
> 
> diff --git a/fs/ext3/dir.c b/fs/ext3/dir.c
> index 87eccbb..83df29f 100644
> --- a/fs/ext3/dir.c
> +++ b/fs/ext3/dir.c
> @@ -47,7 +47,7 @@ static unsigned char get_dtype(struct super_block *sb, int filetype)
>   *
>   * Return 1 if it is a dx dir, 0 if not
>   */
> -static int is_dx_dir(struct inode *inode)
> +int is_dx_dir(struct inode *inode)
>  {
>  	struct super_block *sb = inode->i_sb;
>  
> diff --git a/fs/ext3/ext3.h b/fs/ext3/ext3.h
> index e85ff15..f3018f4 100644
> --- a/fs/ext3/ext3.h
> +++ b/fs/ext3/ext3.h
> @@ -220,6 +220,7 @@ struct ext3_new_group_data {
>  #endif
>  #define EXT3_IOC_GETRSVSZ		_IOR('f', 5, long)
>  #define EXT3_IOC_SETRSVSZ		_IOW('f', 6, long)
> +#define EXT3_IOC_32BITHASH		_IO('f', 13)
>  
>  /*
>   * ioctl commands in 32 bit emulation
> @@ -1010,6 +1011,7 @@ extern void ext3_rsv_window_add(struct super_block *sb, struct ext3_reserve_wind
>  extern int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range);
>  
>  /* dir.c */
> +extern int is_dx_dir(struct inode *inode);
>  extern int ext3_check_dir_entry(const char *, struct inode *,
>  				struct ext3_dir_entry_2 *,
>  				struct buffer_head *, unsigned long);
> diff --git a/fs/ext3/ioctl.c b/fs/ext3/ioctl.c
> index 4d96e9a..a7d2b0a 100644
> --- a/fs/ext3/ioctl.c
> +++ b/fs/ext3/ioctl.c
> @@ -251,6 +251,39 @@ group_add_out:
>  		mnt_drop_write_file(filp);
>  		return err;
>  	}
> +	case EXT3_IOC_32BITHASH: {
> +		int err = 0;
> +
> +		/* Serialize with readdir */
> +		if ((err = mutex_lock_killable(&inode->i_mutex)))
> +			return err;
> +
> +		/* protect f_mode */
> +		spin_lock(&filp->f_lock);
> +
> +		/* Only valid for htree directories */
> +		if (!S_ISDIR(inode->i_mode)) {
> +			err = -ENOTDIR;
> +			goto hash32bits_out;
> +		}
> +
> +		if (!is_dx_dir(inode)) {
> +			err = -EINVAL;
> +			goto hash32bits_out;
> +		}
> +
> +		/* Have we already started readdir on this dx dir? */
> +		if (filp->private_data) {
> +			err = -EINVAL;
> +			goto hash32bits_out;
> +		}
> +
> +		filp->f_mode |= FMODE_32BITHASH;
> +hash32bits_out:
> +		spin_unlock(&filp->f_lock);
> +		mutex_unlock(&inode->i_mutex);
> +		return err;
> +	}
>  	case FITRIM: {
>  
>  		struct super_block *sb = inode->i_sb;
> 
> 
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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