NFSD: reduce locking in nfsd_lookup()

nfsd_lookup() takes an exclusive lock on the parent inode, but no
callers want the lock and it may not be needed at all if the
result is in the dcache.

Change nfsd_lookup_dentry() to not take the lock, and call
lookup_one_len_locked() which takes lock only if needed.

nfsd4_open() currently expects the lock to still be held, but that isn't
necessary as nfsd_validate_delegated_dentry() provides required
guarantees without the lock.

NOTE: NFSv4 requires directory changeinfo for OPEN even when a create
  wasn't requested and no change happened.  Now that nfsd_lookup()
  doesn't use fh_lock(), we need to explicitly fill the attributes
  when no create happens.  A new fh_fill_both_attrs() is provided
  for that task.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 5e2ed4b2a925..cd2946a88d72 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -672,6 +672,25 @@ void fh_fill_post_attrs(struct svc_fh *fhp)
 			nfsd4_change_attribute(&fhp->fh_post_attr, inode);
 }
 
+/**
+ * fh_fill_both_attrs - Fill pre-op and post-op attributes
+ * @fhp: file handle to be updated
+ *
+ * This is used when the directory wasn't changed, but wcc attributes
+ * are needed anyway.
+ */
+void fh_fill_both_attrs(struct svc_fh *fhp)
+{
+	fh_fill_post_attrs(fhp);
+	if (!fhp->fh_post_saved)
+		return;
+	fhp->fh_pre_change = fhp->fh_post_change;
+	fhp->fh_pre_mtime = fhp->fh_post_attr.mtime;
+	fhp->fh_pre_ctime = fhp->fh_post_attr.ctime;
+	fhp->fh_pre_size = fhp->fh_post_attr.size;
+	fhp->fh_pre_saved = true;
+}
+
 /*
  * Release a file handle.
  */