[PATCH] r/o bind mounts: get callers of vfs_mknod/create/mkdir()

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().

So that we don't have to make three mnt_want/drop_write()
calls inside of the switch statement, we move some of its
logic outside of the switch and into a helper function
suggested by Christoph.

This also encapsulates a fix for mknod(S_IFREG) that Miklos
found.

[AV: merged mkdir handling, added missing nfsd pieces]

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 26 insertions, 2 deletions

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 4e77a1a3bd73..145b3c877a27 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -155,7 +155,11 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
 		dprintk("NFSD: nfsd4_create_clid_dir: DIRECTORY EXISTS\n");
 		goto out_put;
 	}
+	status = mnt_want_write(rec_dir.path.mnt);
+	if (status)
+		goto out_put;
 	status = vfs_mkdir(rec_dir.path.dentry->d_inode, dentry, S_IRWXU);
+	mnt_drop_write(rec_dir.path.mnt);
 out_put:
 	dput(dentry);
 out_unlock:
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index efff58a5818c..14d582467029 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1255,23 +1255,35 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	err = 0;
 	switch (type) {
 	case S_IFREG:
+		host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+		if (host_err)
+			goto out_nfserr;
 		host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
 		break;
 	case S_IFDIR:
+		host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+		if (host_err)
+			goto out_nfserr;
 		host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
 		break;
 	case S_IFCHR:
 	case S_IFBLK:
 	case S_IFIFO:
 	case S_IFSOCK:
+		host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+		if (host_err)
+			goto out_nfserr;
 		host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
 		break;
 	default:
 	        printk("nfsd: bad file type %o in nfsd_create\n", type);
 		host_err = -EINVAL;
+		goto out_nfserr;
 	}
-	if (host_err < 0)
+	if (host_err < 0) {
+		mnt_drop_write(fhp->fh_export->ex_path.mnt);
 		goto out_nfserr;
+	}
 
 	if (EX_ISSYNC(fhp->fh_export)) {
 		err = nfserrno(nfsd_sync_dir(dentry));
@@ -1282,6 +1294,7 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	err2 = nfsd_create_setattr(rqstp, resfhp, iap);
 	if (err2)
 		err = err2;
+	mnt_drop_write(fhp->fh_export->ex_path.mnt);
 	/*
 	 * Update the file handle to get the new inode info.
 	 */
@@ -1359,6 +1372,9 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		v_atime = verifier[1]&0x7fffffff;
 	}
 	
+	host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+	if (host_err)
+		goto out_nfserr;
 	if (dchild->d_inode) {
 		err = 0;
 
@@ -1390,12 +1406,15 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		case NFS3_CREATE_GUARDED:
 			err = nfserr_exist;
 		}
+		mnt_drop_write(fhp->fh_export->ex_path.mnt);
 		goto out;
 	}
 
 	host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
-	if (host_err < 0)
+	if (host_err < 0) {
+		mnt_drop_write(fhp->fh_export->ex_path.mnt);
 		goto out_nfserr;
+	}
 	if (created)
 		*created = 1;
 
@@ -1420,6 +1439,7 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (err2)
 		err = err2;
 
+	mnt_drop_write(fhp->fh_export->ex_path.mnt);
 	/*
 	 * Update the filehandle to get the new inode info.
 	 */