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@xxxxxxx>
> ---
> 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
>
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