[PATCH 16/22] sys_mknodat(): elevate write count for vfs_mknod/create()

[Dave Hansen <hansendc@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      |    4 ++++
 lxc-dave/net/unix/af_unix.c |    4 ++++
 3 files changed, 20 insertions(+)

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	2007-02-09 14:26:57.000000000 -0800
+++ lxc-dave/fs/namei.c	2007-02-09 14:26:57.000000000 -0800
@@ -1903,14 +1903,26 @@ 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	2007-02-09 14:26:57.000000000 -0800
+++ lxc-dave/fs/nfsd/vfs.c	2007-02-09 14:26:57.000000000 -0800
@@ -664,6 +664,9 @@ nfsd_open(struct svc_rqst *rqstp, struct
 	/* Disallow write access to files with the append-only bit set
 	 * or any access when mandatory locking enabled
 	 */
+	err = mnt_want_write(fhp->fh_export->ex_mnt);
+	if (err)
+		goto out_nfserr;
 	err = nfserr_perm;
 	if (IS_APPEND(inode) && (access & MAY_WRITE))
 		goto out;
@@ -1199,6 +1202,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
 	        printk("nfsd: bad file type %o in nfsd_create\n", type);
 		host_err = -EINVAL;
 	}
+	mnt_drop_write(fhp->fh_export->ex_mnt);
 	if (host_err < 0)
 		goto out_nfserr;
 
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	2007-02-09 14:26:57.000000000 -0800
+++ lxc-dave/net/unix/af_unix.c	2007-02-09 14:26:57.000000000 -0800
@@ -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);
_
-
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