NFSD: Fix READDIR on NFSv3 mounts of ext4 exports

I noticed that recently, simple operations like "make" started
failing on NFSv3 mounts of ext4 exports. Network capture shows that
READDIRPLUS operated correctly but READDIR failed with
NFS3ERR_INVAL. The vfs_llseek() call returned EINVAL when it is
passed a non-zero starting directory cookie.

I bisected to commit c689bdd3bffa ("nfsd: further centralize
protocol version checks.").

Turns out that nfsd3_proc_readdir() does not call fh_verify() before
it calls nfsd_readdir(), so the new fhp->fh_64bit_cookies boolean is
not set properly. This leaves the NFSD_MAY_64BIT_COOKIE unset when
the directory is opened.

For ext4, this causes the wrong "max file size" value to be used
when sanity checking the incoming directory cookie (which is a seek
offset value).

The fhp->fh_64bit_cookies boolean is /always/ properly initialized
after nfsd_open() returns. There doesn't seem to be a reason for the
generic NFSD open helper to handle the f_mode fix-up for
directories, so just move that to the one caller that tries to open
an S_IFDIR with NFSD_MAY_64BIT_COOKIE.

Suggested-by: NeilBrown <neilb@suse.de>
Fixes: c689bdd3bffa ("nfsd: further centralize protocol version checks.")
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 22325b590e17f0f36a35a8ced55e4d72974ca5d6..d6d4f2a0e898267816538bdb9416fbdf1dc8c5ed 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -903,11 +903,6 @@ __nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
                goto out;
        }
 
-       if (may_flags & NFSD_MAY_64BIT_COOKIE)
-               file->f_mode |= FMODE_64BITHASH;
-       else
-               file->f_mode |= FMODE_32BITHASH;
-
        *filp = file;
 out:
        return host_err;
@@ -2174,13 +2169,15 @@ nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp,
        loff_t          offset = *offsetp;
        int             may_flags = NFSD_MAY_READ;
 
-       if (fhp->fh_64bit_cookies)
-               may_flags |= NFSD_MAY_64BIT_COOKIE;
-
        err = nfsd_open(rqstp, fhp, S_IFDIR, may_flags, &file);
        if (err)
                goto out;
 
+       if (fhp->fh_64bit_cookies)
+               file->f_mode |= FMODE_64BITHASH;
+       else
+               file->f_mode |= FMODE_32BITHASH;
+
        offset = vfs_llseek(file, offset, SEEK_SET);
        if (offset < 0) {
                err = nfserrno((int)offset);