xfs: fix behaviour of XFS_IOC_FSSETXATTR on directories

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@k1024.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 25 insertions, 14 deletions

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 1f186d2eec06..0f6b6abb7c7a 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,