[RFC PATCH 4/4] NFSD: Return NFS4ERR_FILE_OPEN only when linking an open file

cel
2025-01-23T19:52:50Z

From: Chuck Lever <chuck.lever@oracle.com>

RFC 8881 Section 18.9.4 paragraphs 1 - 2 tell us that RENAME should
return NFS4ERR_FILE_OPEN only when the target object is a file that
is currently open. If the target is a directory, some other status
must be returned.

Generally I expect that a delegation recall will be triggered in
some of these circumstances. In other cases, the VFS might return
-EBUSY for other reasons, and NFSD has to ensure that errno does
not leak to clients as a status code that is not permitted by spec.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/nfsd/vfs.c | 44 +++++++++++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 5cfb5eb54c23..566b9adf2259 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1699,9 +1699,17 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
return err;
}

-/*
- * Create a hardlink
- * N.B. After this call _both_ ffhp and tfhp need an fh_put
+/**
+ * nfsd_link - create a link
+ * @rqstp: RPC transaction context
+ * @ffhp: the file handle of the directory where the new link is to be created
+ * @name: the filename of the new link
+ * @len: the length of @name in octets
+ * @tfhp: the file handle of an existing file object
+ *
+ * After this call _both_ ffhp and tfhp need an fh_put.
+ *
+ * Returns a generic NFS status code in network byte-order.
*/
__be32
nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
@@ -1709,6 +1717,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
{
struct dentry *ddir, *dnew, *dold;
struct inode *dirp;
+ int type;
__be32 err;
int host_err;

@@ -1728,11 +1737,11 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
if (isdotent(name, len))
goto out;

+ err = nfs_ok;
+ type = d_inode(tfhp->fh_dentry)->i_mode & S_IFMT;
host_err = fh_want_write(tfhp);
- if (host_err) {
- err = nfserrno(host_err);
+ if (host_err)
goto out;
- }

ddir = ffhp->fh_dentry;
dirp = d_inode(ddir);
@@ -1740,7 +1749,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,

dnew = lookup_one_len(name, ddir, len);
if (IS_ERR(dnew)) {
- err = nfserrno(PTR_ERR(dnew));
+ host_err = PTR_ERR(dnew);
goto out_unlock;
}

@@ -1756,17 +1765,26 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
fh_fill_post_attrs(ffhp);
inode_unlock(dirp);
if (!host_err) {
- err = nfserrno(commit_metadata(ffhp));
- if (!err)
- err = nfserrno(commit_metadata(tfhp));
- } else {
- err = nfserrno(host_err);
+ host_err = commit_metadata(ffhp);
+ if (!host_err)
+ host_err = commit_metadata(tfhp);
}
+
dput(dnew);
out_drop_write:
fh_drop_write(tfhp);
+ if (host_err == -EBUSY) {
+ /*
+ * See RFC 8881 Section 18.9.4 para 1-2: NFSv4 LINK
+ * status distinguishes between reg file and dir.
+ */
+ if (type != S_IFDIR)
+ err = nfserr_file_open;
+ else
+ err = nfserr_acces;
+ }
out:
- return err;
+ return err != nfs_ok ? err : nfserrno(host_err);

out_dput:
dput(dnew);
--
2.47.0