[PATCH 22/26] sys_mknodat(): elevate write count for vfs_mknod/create()

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

This takes care of all of the direct callers of vfs_mknod().
Since a few of these cases also handle normal file creation
as well, this also covers some calls to vfs_create().

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

 lxc-dave/fs/namei.c         |   12 ++++++++++++
 lxc-dave/fs/nfsd/vfs.c      |    8 ++++++--
 lxc-dave/net/unix/af_unix.c |    4 ++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff -puN fs/namei.c~18-24-sys-mknodat-elevate-write-count-for-vfs-mknod-create fs/namei.c
--- lxc/fs/namei.c~18-24-sys-mknodat-elevate-write-count-for-vfs-mknod-create	2007-06-21 23:23:25.000000000 -0700
+++ lxc-dave/fs/namei.c	2007-06-21 23:23:25.000000000 -0700
@@ -1897,14 +1897,26 @@ asmlinkage long sys_mknodat(int dfd, con
 	if (!IS_ERR(dentry)) {
 		switch (mode & S_IFMT) {
 		case 0: case S_IFREG:
+			error = mnt_want_write(nd.mnt);
+			if (error)
+				break;
 			error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
+			mnt_drop_write(nd.mnt);
 			break;
 		case S_IFCHR: case S_IFBLK:
+			error = mnt_want_write(nd.mnt);
+			if (error)
+				break;
 			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
 					new_decode_dev(dev));
+			mnt_drop_write(nd.mnt);
 			break;
 		case S_IFIFO: case S_IFSOCK:
+			error = mnt_want_write(nd.mnt);
+			if (error)
+				break;
 			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
+			mnt_drop_write(nd.mnt);
 			break;
 		case S_IFDIR:
 			error = -EPERM;
diff -puN fs/nfsd/vfs.c~18-24-sys-mknodat-elevate-write-count-for-vfs-mknod-create fs/nfsd/vfs.c
--- lxc/fs/nfsd/vfs.c~18-24-sys-mknodat-elevate-write-count-for-vfs-mknod-create	2007-06-21 23:23:25.000000000 -0700
+++ lxc-dave/fs/nfsd/vfs.c	2007-06-21 23:23:25.000000000 -0700
@@ -1192,7 +1192,11 @@ nfsd_create(struct svc_rqst *rqstp, stru
 	case S_IFBLK:
 	case S_IFIFO:
 	case S_IFSOCK:
+		host_err = mnt_want_write(fhp->fh_export->ex_mnt);
+		if (host_err)
+			break;
 		host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
+		mnt_drop_write(fhp->fh_export->ex_mnt);
 		break;
 	default:
 	        printk("nfsd: bad file type %o in nfsd_create\n", type);
@@ -1811,7 +1815,7 @@ nfsd_permission(struct svc_export *exp, 
 		inode->i_mode,
 		IS_IMMUTABLE(inode)?	" immut" : "",
 		IS_APPEND(inode)?	" append" : "",
-		__mnt_is_readonly(exp->mnt)?	" 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
@@ -1822,7 +1826,7 @@ nfsd_permission(struct svc_export *exp, 
 	 */
 	if (!(acc & MAY_LOCAL_ACCESS))
 		if (acc & (MAY_WRITE | MAY_SATTR | MAY_TRUNC)) {
-			if (EX_RDONLY(exp) || __mnt_is_readonly(exp->mnt))
+			if (EX_RDONLY(exp) || __mnt_is_readonly(exp->ex_mnt))
 				return nfserr_rofs;
 			if (/* (acc & MAY_WRITE) && */ IS_IMMUTABLE(inode))
 				return nfserr_perm;
diff -puN net/unix/af_unix.c~18-24-sys-mknodat-elevate-write-count-for-vfs-mknod-create net/unix/af_unix.c
--- lxc/net/unix/af_unix.c~18-24-sys-mknodat-elevate-write-count-for-vfs-mknod-create	2007-06-21 23:23:25.000000000 -0700
+++ lxc-dave/net/unix/af_unix.c	2007-06-21 23:23:25.000000000 -0700
@@ -816,7 +816,11 @@ static int unix_bind(struct socket *sock
 		 */
 		mode = S_IFSOCK |
 		       (SOCK_INODE(sock)->i_mode & ~current->fs->umask);
+		err = mnt_want_write(nd.mnt);
+		if (err)
+			goto out_mknod_dput;
 		err = vfs_mknod(nd.dentry->d_inode, dentry, mode, 0);
+		mnt_drop_write(nd.mnt);
 		if (err)
 			goto out_mknod_dput;
 		mutex_unlock(&nd.dentry->d_inode->i_mutex);
_