[PATCH 17/26] elevate write count over calls to vfs_rename()

[Dave Hansen <haveblue@us.ibm.com>]

This also creates a little helper in the NFS code to
make an if() a little bit less ugly.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

 lxc-dave/fs/namei.c    |    4 ++++
 lxc-dave/fs/nfsd/vfs.c |   23 +++++++++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff -puN fs/namei.c~13-24-elevate-write-count-over-calls-to-vfs-rename fs/namei.c
--- lxc/fs/namei.c~13-24-elevate-write-count-over-calls-to-vfs-rename	2007-06-21 23:23:22.000000000 -0700
+++ lxc-dave/fs/namei.c	2007-06-21 23:23:22.000000000 -0700
@@ -2575,8 +2575,12 @@ static int do_rename(int olddfd, const c
 	if (new_dentry == trap)
 		goto exit5;
 
+	error = mnt_want_write(oldnd.mnt);
+	if (error)
+		goto exit5;
 	error = vfs_rename(old_dir->d_inode, old_dentry,
 				   new_dir->d_inode, new_dentry);
+	mnt_drop_write(oldnd.mnt);
 exit5:
 	dput(new_dentry);
 exit4:
diff -puN fs/nfsd/vfs.c~13-24-elevate-write-count-over-calls-to-vfs-rename fs/nfsd/vfs.c
--- lxc/fs/nfsd/vfs.c~13-24-elevate-write-count-over-calls-to-vfs-rename	2007-06-21 23:23:22.000000000 -0700
+++ lxc-dave/fs/nfsd/vfs.c	2007-06-21 23:23:22.000000000 -0700
@@ -1554,6 +1554,14 @@ out_nfserr:
 	goto out_unlock;
 }
 
+static inline int svc_msnfs(struct svc_fh *ffhp)
+{
+#ifdef MSNFS
+	return (ffhp->fh_export->ex_flags & NFSEXP_MSNFS);
+#else
+	return 0;
+#endif
+}
 /*
  * Rename a file
  * N.B. After this call _both_ ffhp and tfhp need an fh_put
@@ -1615,13 +1623,20 @@ nfsd_rename(struct svc_rqst *rqstp, stru
 	if (ndentry == trap)
 		goto out_dput_new;
 
-#ifdef MSNFS
-	if ((ffhp->fh_export->ex_flags & NFSEXP_MSNFS) &&
+	if (svc_msnfs(ffhp) &&
 		((atomic_read(&odentry->d_count) > 1)
 		 || (atomic_read(&ndentry->d_count) > 1))) {
 			host_err = -EPERM;
-	} else
-#endif
+			goto out_dput_new;
+	}
+
+	host_err = -EXDEV;
+	if (ffhp->fh_export->ex_mnt != tfhp->fh_export->ex_mnt)
+		goto out_dput_new;
+	host_err = mnt_want_write(ffhp->fh_export->ex_mnt);
+	if (host_err)
+		goto out_dput_new;
+
 	host_err = vfs_rename(fdir, odentry, tdir, ndentry);
 	if (!host_err && EX_ISSYNC(tfhp->fh_export)) {
 		host_err = nfsd_sync_dir(tdentry);
_