[PATCH 16/24] nfs: check mnt instead of superblock directly

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

If we depend on the inodes for writeability, we will not
catch the r/o mounts when implemented.

This patches uses __mnt_want_write().  It does not guarantee
that the mount will stay writeable after the check.  But,
this is OK for one of the checks because it is just for a
printk().

The other two are probably unnecessary and duplicate existing
checks in the VFS.  This won't make them better checks than
before, but it will make them detect r/o mounts.

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

 lxc-dave/fs/nfs/dir.c  |    3 ++-
 lxc-dave/fs/nfsd/vfs.c |    4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff -puN fs/nfs/dir.c~nfs-check-mnt-instead-of-sb fs/nfs/dir.c
--- lxc/fs/nfs/dir.c~nfs-check-mnt-instead-of-sb	2007-09-17 09:44:05.000000000 -0700
+++ lxc-dave/fs/nfs/dir.c	2007-09-17 09:44:05.000000000 -0700
@@ -997,7 +997,8 @@ static int is_atomic_open(struct inode *
 	if (nd->flags & LOOKUP_DIRECTORY)
 		return 0;
 	/* Are we trying to write to a read only partition? */
-	if (IS_RDONLY(dir) && (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
+	if (__mnt_is_readonly(nd->mnt) &&
+	    (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
 		return 0;
 	return 1;
 }
diff -puN fs/nfsd/vfs.c~nfs-check-mnt-instead-of-sb fs/nfsd/vfs.c
--- lxc/fs/nfsd/vfs.c~nfs-check-mnt-instead-of-sb	2007-09-17 09:44:05.000000000 -0700
+++ lxc-dave/fs/nfsd/vfs.c	2007-09-17 09:44:05.000000000 -0700
@@ -1853,7 +1853,7 @@ nfsd_permission(struct svc_rqst *rqstp, 
 		inode->i_mode,
 		IS_IMMUTABLE(inode)?	" immut" : "",
 		IS_APPEND(inode)?	" append" : "",
-		IS_RDONLY(inode)?	" ro" : "");
+		__mnt_is_readonly(exp->ex_mnt)?	" ro" : "");
 	dprintk("      owner %d/%d user %d/%d\n",
 		inode->i_uid, inode->i_gid, current->fsuid, current->fsgid);
 #endif
@@ -1864,7 +1864,7 @@ nfsd_permission(struct svc_rqst *rqstp, 
 	 */
 	if (!(acc & MAY_LOCAL_ACCESS))
 		if (acc & (MAY_WRITE | MAY_SATTR | MAY_TRUNC)) {
-			if (exp_rdonly(rqstp, exp) || IS_RDONLY(inode))
+			if (exp_rdonly(rqstp, exp) || __mnt_is_readonly(exp->ex_mnt))
 				return nfserr_rofs;
 			if (/* (acc & MAY_WRITE) && */ IS_IMMUTABLE(inode))
 				return nfserr_perm;
_