[PATCH] NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check

[Mike Snitzer <snitzer@kernel.org>]

The header for commit e75b23f9e323 ("nfsd: check d_can_lookup in
fh_verify of directories") details the assumption that justified
adding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is
invalid (in the case of NFS reexport).

When NFSD exports an NFS filesystem it is very possible for
nfsd_mode_check() to encounter a @dentry that doesn't have
i_op->lookup (see nfs_fhget()'s NFS_ATTR_FATTR_MOUNTPOINT and
NFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()).

So remove nfsd_mode_check()'s WARN_ON_ONCE().

Fixes: e75b23f9e323 ("nfsd: check d_can_lookup in fh_verify of directories")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
 fs/nfsd/nfsfh.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index bce8784aa92e4..ffe7f22693edf 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -70,10 +70,8 @@ nfsd_mode_check(struct dentry *dentry, umode_t requested)
 	if (requested == 0) /* the caller doesn't care */
 		return nfs_ok;
 	if (mode == requested) {
-		if (mode == S_IFDIR && !d_can_lookup(dentry)) {
-			WARN_ON_ONCE(1);
+		if (mode == S_IFDIR && !d_can_lookup(dentry))
 			return nfserr_notdir;
-		}
 		return nfs_ok;
 	}
 	if (mode == S_IFLNK) {
-- 
2.44.0