knfsd: nfsd: make all exp_finding functions return -errno's on err

Currently exp_find(), exp_get_by_name(), and friends, return an export on
success, and on failure return:

	errors -EAGAIN (drop this request pending an upcall) or
		-ETIMEDOUT (an upcall has timed out), or
	return NULL, which can mean either that there was a memory allocation
		failure, or that an export was not found, or that a passed-in
		export lacks an auth_domain.

Many callers seem to assume that NULL means that an export was not found,
which may lead to bugs in the case of a memory allocation failure.

Modify these functions to distinguish between the two NULL cases by returning
either -ENOENT or -ENOMEM.  They now never return NULL.  We get to simplify
some code in the process.

We return -ENOENT in the case of a missing auth_domain.  This case should
probably be removed (or converted to a bug) after confirming that it can never
happen.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 5 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 8d6b5c483ae1..0a18149ce963 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -192,15 +192,14 @@ nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
 
                         exp2 = exp_parent(exp->ex_client, mnt, dentry,
                                           &rqstp->rq_chandle);
-                        if (IS_ERR(exp2)) {
+                        if (PTR_ERR(exp2) == -ENOENT) {
+                                dput(dentry);
+                                dentry = dget(dparent);
+                        } else if (IS_ERR(exp2)) {
                                 host_err = PTR_ERR(exp2);
                                 dput(dentry);
                                 mntput(mnt);
                                 goto out_nfserr;
-                        }
-                        if (!exp2) {
-                                dput(dentry);
-                                dentry = dget(dparent);
                         } else {
                                 exp_put(exp);
                                 exp = exp2;