FAILED: patch "[PATCH] nfsd4: use recall_lock for delegation hashing" failed to apply to 3.15-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 3.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 931ee56c67573eb4e51c8a4e78598d965b8b059e Mon Sep 17 00:00:00 2001
From: Benny Halevy <bhalevy@xxxxxxxxxxxxxxx>
Date: Fri, 30 May 2014 09:09:27 -0400
Subject: [PATCH] nfsd4: use recall_lock for delegation hashing

This fixes a bug in the handling of the fi_delegations list.

nfs4_setlease does not hold the recall_lock when adding to it. The
client_mutex is held, which prevents against concurrent list changes,
but nfsd_break_deleg_cb does not hold while walking it. New delegations
could theoretically creep onto the list while we're walking it there.

Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 01a0e4384500..05ca64c4599d 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -433,12 +433,21 @@ static void unhash_stid(struct nfs4_stid *s)
 	s->sc_type = 0;
 }
 
+static void
+hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
+{
+	lockdep_assert_held(&recall_lock);
+
+	list_add(&dp->dl_perfile, &fp->fi_delegations);
+	list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
+}
+
 /* Called under the state lock. */
 static void
 unhash_delegation(struct nfs4_delegation *dp)
 {
-	list_del_init(&dp->dl_perclnt);
 	spin_lock(&recall_lock);
+	list_del_init(&dp->dl_perclnt);
 	list_del_init(&dp->dl_perfile);
 	list_del_init(&dp->dl_recall_lru);
 	spin_unlock(&recall_lock);
@@ -3065,11 +3074,12 @@ static int nfs4_setlease(struct nfs4_delegation *dp)
 	status = vfs_setlease(fl->fl_file, fl->fl_type, &fl);
 	if (status)
 		goto out_free;
-	list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
 	fp->fi_lease = fl;
 	fp->fi_deleg_file = get_file(fl->fl_file);
 	atomic_set(&fp->fi_delegees, 1);
-	list_add(&dp->dl_perfile, &fp->fi_delegations);
+	spin_lock(&recall_lock);
+	hash_delegation_locked(dp, fp);
+	spin_unlock(&recall_lock);
 	return 0;
 out_free:
 	locks_free_lock(fl);
@@ -3090,9 +3100,8 @@ static int nfs4_set_delegation(struct nfs4_delegation *dp, struct nfs4_file *fp)
 		spin_unlock(&recall_lock);
 		return -EAGAIN;
 	}
-	list_add(&dp->dl_perfile, &fp->fi_delegations);
+	hash_delegation_locked(dp, fp);
 	spin_unlock(&recall_lock);
-	list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
 	return 0;
 }
 
@@ -4903,6 +4912,7 @@ static u64 nfsd_find_all_delegations(struct nfs4_client *clp, u64 max,
 	struct nfs4_delegation *dp, *next;
 	u64 count = 0;
 
+	lockdep_assert_held(&recall_lock);
 	list_for_each_entry_safe(dp, next, &clp->cl_delegations, dl_perclnt) {
 		if (victims)
 			list_move(&dp->dl_recall_lru, victims);

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