[PATCH] xfs_dm_rdwr() needs to pass a vfsmount to dentry_open()

[Lachlan McIlroy <lachlan@xxxxxxx>]

There's a new check added to dentry_open():

   if (!mnt) {
       printk(KERN_WARNING "%s called with NULL vfsmount\n", __func__);
       dump_stack();
       return ERR_PTR(-EINVAL);
   }

We need to pass a mountpoint in the call to dentry_open() in xfs_dm_rdwr()
to avoid this code.

--- fs/xfs/dmapi/xfs_dm.c_1.72  2008-05-15 13:23:41.000000000 +1000
+++ fs/xfs/dmapi/xfs_dm.c       2008-05-15 17:51:41.000000000 +1000
@@ -52,6 +52,8 @@
#include <dmapi_kern.h>
#include "xfs_dm.h"

+#include <linux/mount.h>
+
#define MAXNAMLEN MAXNAMELEN

#define MIN_DIO_SIZE(mp)                ((mp)->m_sb.sb_sectsize)
@@ -1121,7 +1123,7 @@ xfs_dm_rdwr(
                return ENOMEM;
        }

-       file = dentry_open(dentry, NULL, oflags);
+       file = dentry_open(dentry, mntget(ip->i_mount->m_vfsmount), oflags);
        if (IS_ERR(file)) {
                return -PTR_ERR(file);
        }
--- fs/xfs/linux-2.6/xfs_super.c_1.416  2008-05-15 13:23:43.000000000 +1000
+++ fs/xfs/linux-2.6/xfs_super.c        2008-05-15 13:29:49.000000000 +1000
@@ -1397,8 +1397,14 @@ xfs_fs_get_sb(
        void                    *data,
        struct vfsmount         *mnt)
{
-       return get_sb_bdev(fs_type, flags, dev_name, data, xfs_fs_fill_super,
+       int     error;
+
+       error = get_sb_bdev(fs_type, flags, dev_name, data, xfs_fs_fill_super,
                           mnt);
+       if (!error)
+               ((struct xfs_mount *)mnt->mnt_sb->s_fs_info)->m_vfsmount = mnt;
+
+       return error;
}

static struct super_operations xfs_super_operations = {
--- fs/xfs/xfs_mount.h_1.265    2008-05-15 13:23:49.000000000 +1000
+++ fs/xfs/xfs_mount.h  2008-05-15 13:21:50.000000000 +1000
@@ -337,6 +337,7 @@ typedef struct xfs_mount {
        spinlock_t              m_sync_lock;    /* work item list lock */
        int                     m_sync_seq;     /* sync thread generation no. */
        wait_queue_head_t       m_wait_single_sync_task;
+       struct vfsmount         *m_vfsmount;
} xfs_mount_t;

/*