nfsd: generate pre-modify path permission events

When modifying local filesystem via nfsd, call fh_want_write() wrappers
to notify listeners on modification intent.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>

fs/nfsd/nfs2acl.c

@@ -107,7 +107,7 @@ static __be32 nfsacld_proc_setacl(struct svc_rqst *rqstp)
 
 	inode = d_inode(fh->fh_dentry);
 
-	error = fh_want_write(fh);
+	error = fh_want_write(fh, ATTR_OTHER);
 	if (error)
 		goto out_errno;
 

fs/nfsd/nfs3acl.c

@@ -97,7 +97,7 @@ static __be32 nfsd3_proc_setacl(struct svc_rqst *rqstp)
 
 	inode = d_inode(fh->fh_dentry);
 
-	error = fh_want_write(fh);
+	error = fh_want_write(fh, ATTR_OTHER);
 	if (error)
 		goto out_errno;
 

fs/nfsd/nfs3proc.c

@@ -256,7 +256,7 @@ nfsd3_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	parent = fhp->fh_dentry;
 	inode = d_inode(parent);
 
-	host_err = fh_want_write(fhp);
+	host_err = fh_want_write(fhp, 0);
 	if (host_err)
 		return nfserrno(host_err);
 

fs/nfsd/nfs4proc.c

@@ -254,7 +254,7 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	parent = fhp->fh_dentry;
 	inode = d_inode(parent);
 
-	host_err = fh_want_write(fhp);
+	host_err = fh_want_write(fhp, 0);
 	if (host_err)
 		return nfserrno(host_err);
 
@@ -1113,7 +1113,7 @@ nfsd4_setattr(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 			return status;
 		}
 	}
-	err = fh_want_write(&cstate->current_fh);
+	err = fh_want_write(&cstate->current_fh, setattr->sa_iattr.ia_valid);
 	if (err)
 		return nfserrno(err);
 	status = nfs_ok;

fs/nfsd/nfsfh.h

@@ -81,7 +81,7 @@ typedef struct svc_fh {
 	struct dentry *		fh_dentry;	/* validated dentry */
 	struct svc_export *	fh_export;	/* export pointer */
 
-	bool			fh_want_write;	/* remount protection taken */
+	int			fh_write_idx;	/* remount protection taken */
 	bool			fh_no_wcc;	/* no wcc data needed */
 	bool			fh_no_atomic_attr;
 						/*

fs/nfsd/nfsproc.c

@@ -286,7 +286,7 @@ nfsd_proc_create(struct svc_rqst *rqstp)
 	resp->status = nfserr_exist;
 	if (isdotent(argp->name, argp->len))
 		goto done;
-	hosterr = fh_want_write(dirfhp);
+	hosterr = fh_want_fname(dirfhp, argp->name, argp->len, MAY_CREATE);
 	if (hosterr) {
 		resp->status = nfserrno(hosterr);
 		goto done;

fs/nfsd/vfs.c

@@ -384,6 +384,73 @@ static int __nfsd_setattr(struct dentry *dentry, struct iattr *iap)
 	return notify_change(&init_user_ns, dentry, iap, NULL);
 }
 
+int fh_want_write(struct svc_fh *fh, unsigned int attr)
+{
+	struct path path;
+	int ret, idx;
+
+	if (fh->fh_write_idx >= 0)
+		return 0;
+
+	path.mnt = fh->fh_export->ex_path.mnt;
+	path.dentry = fh->fh_dentry;
+	ret = mnt_want_write_path_attr(&path, attr, &idx);
+	if (!ret)
+		fh->fh_write_idx = idx;
+	return ret;
+}
+
+int fh_want_fname(struct svc_fh *fh, char *fname, int flen, int mask)
+{
+	struct path path;
+	struct lookup_result res = {
+		.last = { .name = fname, .len = flen }
+	};
+	int ret, idx;
+
+	/*
+	 * XXX: this does not look like it should happen on link/unlink
+	 */
+	if (WARN_ON(fh->fh_write_idx >= 0))
+		return 0;
+
+	path.mnt = fh->fh_export->ex_path.mnt;
+	path.dentry = fh->fh_dentry;
+	ret = mnt_want_write_parent(&path, mask, &res, &idx);
+	if (!ret)
+		fh->fh_write_idx = idx;
+	return ret;
+}
+
+int fh_want_rename(struct svc_fh *ffh, char *fname, int flen,
+			 struct svc_fh *tfh, char *tname, int tlen)
+{
+	struct path oldpath, newpath;
+	struct lookup_result oldres = {
+		.last = { .name = fname, .len = flen }
+	};
+	struct lookup_result newres = {
+		.last = { .name = tname, .len = tlen }
+	};
+	int ret, idx;
+
+	/*
+	 * XXX: this does not look like it should happen on rename
+	 */
+	if (WARN_ON(ffh->fh_write_idx >= 0))
+		return 0;
+
+	oldpath.mnt = ffh->fh_export->ex_path.mnt;
+	oldpath.dentry = ffh->fh_dentry;
+	newpath.mnt = tfh->fh_export->ex_path.mnt;
+	newpath.dentry = tfh->fh_dentry;
+	ret = mnt_want_write_parents(&oldpath, &oldres, &newpath, &newres,
+				     &idx);
+	if (!ret)
+		ffh->fh_write_idx = idx;
+	return ret;
+}
+
 /**
  * nfsd_setattr - Set various file attributes.
  * @rqstp: controlling RPC transaction
@@ -441,7 +508,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (err)
 		return err;
 	if (get_write_count) {
-		host_err = fh_want_write(fhp);
+		host_err = fh_want_write(fhp, iap->ia_valid);
 		if (host_err)
 			goto out;
 	}
@@ -1386,7 +1453,7 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 
 	dentry = fhp->fh_dentry;
 
-	host_err = fh_want_write(fhp);
+	host_err = fh_want_fname(fhp, fname, flen, MAY_CREATE);
 	if (host_err)
 		return nfserrno(host_err);
 
@@ -1486,7 +1553,7 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (err)
 		goto out;
 
-	host_err = fh_want_write(fhp);
+	host_err = fh_want_fname(fhp, fname, flen, MAY_CREATE);
 	if (host_err) {
 		err = nfserrno(host_err);
 		goto out;
@@ -1547,7 +1614,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
 	if (isdotent(name, len))
 		goto out;
 
-	host_err = fh_want_write(tfhp);
+	host_err = fh_want_fname(ffhp, name, len, MAY_CREATE);
 	if (host_err) {
 		err = nfserrno(host_err);
 		goto out;
@@ -1647,7 +1714,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 		goto out;
 
 retry:
-	host_err = fh_want_write(ffhp);
+	host_err = fh_want_rename(ffhp, fname, flen, tfhp, tname, tlen);
 	if (host_err) {
 		err = nfserrno(host_err);
 		goto out;
@@ -1762,7 +1829,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 	if (err)
 		goto out;
 
-	host_err = fh_want_write(fhp);
+	host_err = fh_want_fname(fhp, fname, flen, MAY_DELETE);
 	if (host_err)
 		goto out_nfserr;
 
@@ -2204,7 +2271,7 @@ nfsd_removexattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char *name)
 	if (err)
 		return err;
 
-	ret = fh_want_write(fhp);
+	ret = fh_want_write(fhp, ATTR_OTHER);
 	if (ret)
 		return nfserrno(ret);
 
@@ -2232,7 +2299,7 @@ nfsd_setxattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char *name,
 	if (err)
 		return err;
 
-	ret = fh_want_write(fhp);
+	ret = fh_want_write(fhp, ATTR_OTHER);
 	if (ret)
 		return nfserrno(ret);
 	inode_lock(fhp->fh_dentry->d_inode);

fs/nfsd/vfs.h

@@ -146,23 +146,17 @@ __be32		nfsd_statfs(struct svc_rqst *, struct svc_fh *,
 __be32		nfsd_permission(struct svc_rqst *, struct svc_export *,
 				struct dentry *, int);
 
-static inline int fh_want_write(struct svc_fh *fh)
-{
-	int ret;
-
-	if (fh->fh_want_write)
-		return 0;
-	ret = mnt_want_write(fh->fh_export->ex_path.mnt);
-	if (!ret)
-		fh->fh_want_write = true;
-	return ret;
-}
+int fh_want_write(struct svc_fh *fh, unsigned int attr);
+int fh_want_fname(struct svc_fh *fh, char *fname, int flen, int mask);
+int fh_want_rename(struct svc_fh *ffh, char *fname, int flen,
+		   struct svc_fh *tfh, char *tname, int tlen);
 
 static inline void fh_drop_write(struct svc_fh *fh)
 {
-	if (fh->fh_want_write) {
-		fh->fh_want_write = false;
-		mnt_drop_write(fh->fh_export->ex_path.mnt);
+	if (fh->fh_write_idx >= 0) {
+		mnt_drop_write_idx(fh->fh_export->ex_path.mnt,
+				   fh->fh_write_idx);
+		fh->fh_write_idx = -1;
 	}
 }