nfsd: protect lease-related nfs4_file fields with fi_lock

Currently these fields are protected with the state_lock, but that
doesn't really make a lot of sense. These fields are "private" to the
nfs4_file, and can be protected with the more granular fi_lock.

The fi_lock is already held when setting these fields. Make the code
hold the fp->fi_lock when clearing the lease-related fields in the
nfs4_file, and no longer require that the state_lock be held when
calling into this function.

To prevent lock inversion with the i_lock, we also move the vfs_setlease
and fput calls outside of the fi_lock. This also sets us up for allowing
vfs_setlease calls to block in the future.

Finally, remove a redundant NULL pointer check. unhash_delegation_locked
locks the fp->fi_lock prior to that check, so fp in that function must
never be NULL.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 2e80a59e7e91..309ec3b1090a 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -673,15 +673,20 @@ nfs4_put_stid(struct nfs4_stid *s)
 
 static void nfs4_put_deleg_lease(struct nfs4_file *fp)
 {
-        lockdep_assert_held(&state_lock);
+        struct file *filp = NULL;
+        struct file_lock *fl;
 
-        if (!fp->fi_lease)
-                return;
-        if (atomic_dec_and_test(&fp->fi_delegees)) {
-                vfs_setlease(fp->fi_deleg_file, F_UNLCK, &fp->fi_lease);
+        spin_lock(&fp->fi_lock);
+        if (fp->fi_lease && atomic_dec_and_test(&fp->fi_delegees)) {
+                swap(filp, fp->fi_deleg_file);
+                fl = fp->fi_lease;
                 fp->fi_lease = NULL;
-                fput(fp->fi_deleg_file);
-                fp->fi_deleg_file = NULL;
+        }
+        spin_unlock(&fp->fi_lock);
+
+        if (filp) {
+                vfs_setlease(filp, F_UNLCK, &fl);
+                fput(filp);
         }
 }
 
@@ -717,8 +722,7 @@ unhash_delegation_locked(struct nfs4_delegation *dp)
         list_del_init(&dp->dl_recall_lru);
         list_del_init(&dp->dl_perfile);
         spin_unlock(&fp->fi_lock);
-        if (fp)
-                nfs4_put_deleg_lease(fp);
+        nfs4_put_deleg_lease(fp);
 }
 
 static void destroy_delegation(struct nfs4_delegation *dp)