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Re: [PATCH 9/9] xfs: fix behaviour of XFS_IOC_FSSETXATTR on directories

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 9/9] xfs: fix behaviour of XFS_IOC_FSSETXATTR on directories
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Thu, 29 Jan 2015 10:35:49 -0500
Cc: xfs@xxxxxxxxxxx, iustin@xxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1422328486-24661-10-git-send-email-david@xxxxxxxxxxxxx>
References: <1422328486-24661-1-git-send-email-david@xxxxxxxxxxxxx> <1422328486-24661-10-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Tue, Jan 27, 2015 at 02:14:46PM +1100, Dave Chinner wrote:
> From: Iustin Pop <iustin@xxxxxxxxx>
> 
> Currently, the ioctl handling code for XFS_IOC_FSSETXATTR treats all
> targets as regular files: it refuses to change the extent size if
> extents are allocated. This is wrong for directories, as there the
> extent size is only used as a default for children.
> 
> The patch fixes this issue and improves validation of flag
> combinations:
> 
> - only disallow extent size changes after extents have been allocated
>   for regular files
> - only allow XFS_XFLAG_EXTSIZE for regular files
> - only allow XFS_XFLAG_EXTSZINHERIT for directories
> - automatically clear the flags if the extent size is zero
> 
> Thanks to Dave Chinner for guidance on the proper fix for this issue.
> 
> [dchinner: ported changes onto cleanup series. Makes changes clear
>          and obvious.]
> [dchinner: added comments documenting validity checking rules.]
> 
> Signed-off-by: Iustin Pop <iustin@xxxxxxxxx>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  fs/xfs/xfs_ioctl.c | 39 +++++++++++++++++++++++++--------------
>  1 file changed, 25 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 561d142..5d9dc69 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1098,6 +1098,20 @@ out_cancel:
>       return ERR_PTR(error);
>  }
>  
> +/*
> + * extent size hint validation is somewhat cumbersome. Rules are:
> + *
> + * 1. extent size hint is only valid for directories and regular files
> + * 2. XFS_XFLAG_EXTSIZE is only valid for regular files
> + * 3. XFS_XFLAG_EXTSZINHERIT is only valid for directories.
> + * 4. can only be changed on regular files if no extents are allocated
> + * 5. can be changed on directories at any time
> + * 6. extsize hint of 0 turns off hints, clears inode flags.
> + * 7. Extent size must be a multiple of the appropriate block size.
> + * 8. for non-realtime files, the extent size hint must be limited
> + *    to half the AG size to avoid alignment extending the extent beyond the
> + *    limits of the AG.
> + */
>  int
>  xfs_ioctl_setattr_check_extsize(
>       struct xfs_inode        *ip,
> @@ -1105,20 +1119,17 @@ xfs_ioctl_setattr_check_extsize(
>  {
>       struct xfs_mount        *mp = ip->i_mount;
>  
> -     /* Can't change extent size if any extents are allocated. */
> -     if (ip->i_d.di_nextents &&
> +     if ((fa->fsx_xflags & XFS_XFLAG_EXTSIZE) && !S_ISREG(ip->i_d.di_mode))
> +             return -EINVAL;
> +
> +     if ((fa->fsx_xflags & XFS_XFLAG_EXTSZINHERIT) &&
> +         !S_ISDIR(ip->i_d.di_mode))
> +             return -EINVAL;
> +
> +     if (S_ISREG(ip->i_d.di_mode) && ip->i_d.di_nextents &&
>           ((ip->i_d.di_extsize << mp->m_sb.sb_blocklog) != fa->fsx_extsize))
>               return -EINVAL;
>  
> -     /*
> -      * Extent size must be a multiple of the appropriate block size, if set
> -      * at all. It must also be smaller than the maximum extent size
> -      * supported by the filesystem.
> -      *
> -      * Also, for non-realtime files, limit the extent size hint to half the
> -      * size of the AGs in the filesystem so alignment doesn't result in
> -      * extents larger than an AG.
> -      */
>       if (fa->fsx_extsize != 0) {
>               xfs_extlen_t    size;
>               xfs_fsblock_t   extsize_fsb;
> @@ -1138,7 +1149,9 @@ xfs_ioctl_setattr_check_extsize(
>  
>               if (fa->fsx_extsize % size)
>                       return -EINVAL;
> -     }
> +     } else
> +             fa->fsx_xflags &= ~(XFS_XFLAG_EXTSIZE | XFS_XFLAG_EXTSZINHERIT);
> +
>       return 0;
>  }
>  
> @@ -1169,8 +1182,6 @@ xfs_ioctl_setattr_check_projid(
>       return 0;
>  }
>  
> -
> -
>  STATIC int
>  xfs_ioctl_setattr(
>       xfs_inode_t             *ip,
> -- 
> 2.0.0
> 
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