Re: [PATCH] Btrfs: compressed file size ioctl

[liubo <liubo2009@cn.fujitsu.com>]

On 07/29/2010 07:27 PM, Ulrich Hecht wrote:
> Returns a file's size on disk. Based on a patch by Chris Ball, improved
> following suggestions by Chris Mason and Miao Xie.
>
> Minimal example:
>
>  #include <sys/ioctl.h>
>  #include <fcntl.h>
>  #include <stdint.h>
>  #include <stdio.h>
>  #define BTRFS_IOCTL_MAGIC 0x94
>  #define BTRFS_IOC_COMPR_SIZE   _IOR(BTRFS_IOCTL_MAGIC, 21, uint64_t)
> int main(int argc, char **argv)
> {
>   uint64_t size = -1;
>   int d = open(argv[1], O_RDONLY);
>   ioctl(d, BTRFS_IOC_COMPR_SIZE, &size);
>   printf("%zd\n", size);
>   return 0;
> }
>
> Signed-off-by: Ulrich Hecht <uli@suse.de>
> ---
>  fs/btrfs/ioctl.c |   41 +++++++++++++++++++++++++++++++++++++++++
>  fs/btrfs/ioctl.h |    1 +
>  2 files changed, 42 insertions(+), 0 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 9254b3d..29651c9 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1750,6 +1750,45 @@ out_drop_write:
>  	return ret;
>  }
>  
> +static long btrfs_ioctl_compsize(struct file *file, void __user *argp)
> +{
> +	/* This ioctl returns the compressed size of an inode on disk
> +	 * by counting the on-disk space used by all of its extents.
> +	 */
> +	struct inode *inode = fdentry(file)->d_inode;
> +	struct extent_map *em;
> +	u64 len = inode->i_size;
> +	u64 compressed_size = 0;
> +	u64 offset = 0;
> +
> +	if (S_ISDIR(inode->i_mode))
> +		return -EISDIR;
> +	
> +	mutex_lock(&inode->i_mutex);
> +
> +	/* do any pending delalloc/csum calc on inode, one way or
> +	   another, and lock file content */
> +	btrfs_wait_ordered_range(inode, 0, (u64)-1);
> +
> +	while (offset < len) {
> +		em = btrfs_get_extent(inode, NULL, 0, offset, 1, 0);
> +		BUG_ON(IS_ERR(em) || !em);
> +		if (em->block_len != (u64)-1)
> +			compressed_size += em->block_len;
> +		offset += em->len;
> +		free_extent_map(em);
> +	}
> +	mutex_unlock(&inode->i_mutex);
> +
> +	unlock_extent(&BTRFS_I(inode)->io_tree, 0, len, GFP_NOFS);
> +
> +	/* We've succeeded in going through all extents; set the final size. */
> +	if (copy_to_user(argp, &compressed_size, sizeof(compressed_size)))
> +		return -EFAULT;
> +	else
>   

BTW, this "else" can be dropped. :-)

Thanks,
liubo

> +		return 0;
> +}
> +
>  static long btrfs_ioctl_clone_range(struct file *file, void __user *argp)
>  {
>  	struct btrfs_ioctl_clone_range_args args;
> @@ -2034,6 +2073,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>  	case BTRFS_IOC_SYNC:
>  		btrfs_sync_fs(file->f_dentry->d_sb, 1);
>  		return 0;
> +	case BTRFS_IOC_COMPR_SIZE:
> +		return btrfs_ioctl_compsize(file, argp);
>  	}
>  
>  	return -ENOTTY;
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 424694a..a01ef1e 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -178,4 +178,5 @@ struct btrfs_ioctl_space_args {
>  #define BTRFS_IOC_DEFAULT_SUBVOL _IOW(BTRFS_IOCTL_MAGIC, 19, u64)
>  #define BTRFS_IOC_SPACE_INFO _IOWR(BTRFS_IOCTL_MAGIC, 20, \
>  				    struct btrfs_ioctl_space_args)
> +#define BTRFS_IOC_COMPR_SIZE _IOR(BTRFS_IOCTL_MAGIC, 21, u64)
>  #endif
>