[PATCH] xfs: fix behaviour of XFS_IOC_FSSETXATTR on directories

[Iustin Pop <iusty@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 by only checking for allocated extents for regular
files; it leaves undefined what it means to set an extent size on a
non-regular, non-directory inode. Additionally, when setting a non-zero
extent size, the appropriate flags (EXTSIZE, respectively EXTSZINHERIT)
are enforced for regular files and directories.

Signed-off-by: Iustin Pop <iusty@xxxxxxxxx>
---
 A patch against xfstests to test for the fixed behaviour will follow
 shortly.

 fs/xfs/xfs_ioctl.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 8bc1bbc..5b9acd2 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1116,14 +1116,32 @@ xfs_ioctl_setattr(
        }
 
        if (mask & FSX_EXTSIZE) {
-               /*
-                * Can't change extent size if any extents are allocated.
-                */
-               if (ip->i_d.di_nextents &&
-                   ((ip->i_d.di_extsize << mp->m_sb.sb_blocklog) !=
-                    fa->fsx_extsize)) {
-                       code = XFS_ERROR(EINVAL);       /* EFBIG? */
-                       goto error_return;
+               if (S_ISDIR(ip->i_d.di_mode)) {
+                       /*
+                        * Enforce setting the EXTSZINHERIT flag when
+                        * a non-zero extent size has been specified.
+                        */
+                       if (fa->fsx_extsize) {
+                               fa->fsx_xflags |= XFS_XFLAG_EXTSZINHERIT;
+                       }
+               } else if (S_ISREG(ip->i_d.di_mode)) {
+                       /*
+                        * For a regular file, we can't change extent
+                        * size if any extents are allocated.
+                        */
+                       if (ip->i_d.di_nextents &&
+                           ((ip->i_d.di_extsize << mp->m_sb.sb_blocklog) !=
+                            fa->fsx_extsize)) {
+                               code = XFS_ERROR(EINVAL);       /* EFBIG? */
+                               goto error_return;
+                       }
+                       /*
+                        * Enforce setting the EXTSIZE flag when
+                        * a non-zero extent size has been specified.
+                        */
+                       if (fa->fsx_extsize) {
+                               fa->fsx_xflags |= XFS_XFLAG_EXTSIZE;
+                       }
                }
 
                /*
-- 
2.1.0