From: NeilBrown <neilb@suse.com>
Date: Wed, 13 Dec 2017 09:41:04 +1100
Subject: [PATCH] NFSv4: always set NFS_LOCK_LOST when a lock is lost.
Patch-mainline: v4.16-rc1
Git-commit: dce2630c7da73b0634686bca557cc8945cc450c8
References: bsc#1068951

There are 2 comments in the NFSv4 code which suggest that
SIGLOST should possibly be sent to a process.  In these
cases a lock has been lost.
The current practice is to set NFS_LOCK_LOST so that
read/write returns EIO when a lock is lost.
So change these comments to code when sets NFS_LOCK_LOST.

One case is when lock recovery after apparent server restart fails
with NFS4ERR_DENIED, NFS4ERR_RECLAIM_BAD, NFS4ERRO_RECLAIM_CONFLICT.
The other case is when lease recovery fails with NFS4ERR_DENIED.

In an ideal world, these should not happen.  However I have a packet
trace showing an NFSv4.1 session getting NFS4ERR_BADSESSION after
an extended network parition.  The NFSv4.1 client treats this like
server reboot until/unless it get NFS4ERR_NO_GRACE, in which case
it switches over to "nograce" recovery mode.
In this network trace, the client attempts to recover a lock
and the server (incorrectly) reports NFS4ERR_DENIED rather
than NFS4ERR_NO_GRACE.  This leads to the ineffective comment
and the client then continues to write using the OPEN stateid.

Note that I have not tested this as I do not have direct access to a
faulty NFS server.  Once I get confirmation I will provide an update.

Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/nfs4proc.c  |   12 ++++++++----
 fs/nfs/nfs4state.c |    5 ++++-
 2 files changed, 12 insertions(+), 5 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1784,7 +1784,7 @@ static int nfs4_open_reclaim(struct nfs4
 	return ret;
 }
 
-static int nfs4_handle_delegation_recall_error(struct nfs_server *server, struct nfs4_state *state, const nfs4_stateid *stateid, int err)
+static int nfs4_handle_delegation_recall_error(struct nfs_server *server, struct nfs4_state *state, const nfs4_stateid *stateid, struct file_lock *fl, int err)
 {
 	switch (err) {
 		default:
@@ -1831,7 +1831,11 @@ static int nfs4_handle_delegation_recall
 			return -EAGAIN;
 		case -ENOMEM:
 		case -NFS4ERR_DENIED:
-			/* kill_proc(fl->fl_pid, SIGLOST, 1); */
+			if (fl) {
+				struct nfs4_lock_state *lsp = fl->fl_u.nfs4_fl.owner;
+				if (lsp)
+					set_bit(NFS_LOCK_LOST, &lsp->ls_flags);
+			}
 			return 0;
 	}
 	return err;
@@ -1867,7 +1871,7 @@ int nfs4_open_delegation_recall(struct n
 		err = nfs4_open_recover_helper(opendata, FMODE_READ);
 	}
 	nfs4_opendata_put(opendata);
-	return nfs4_handle_delegation_recall_error(server, state, stateid, err);
+	return nfs4_handle_delegation_recall_error(server, state, stateid, NULL, err);
 }
 
 static void nfs4_open_confirm_prepare(struct rpc_task *task, void *calldata)
@@ -6159,7 +6163,7 @@ int nfs4_lock_delegation_recall(struct f
 	if (err != 0)
 		return err;
 	err = _nfs4_do_setlk(state, F_SETLK, fl, NFS_LOCK_NEW);
-	return nfs4_handle_delegation_recall_error(server, state, stateid, err);
+	return nfs4_handle_delegation_recall_error(server, state, stateid, fl, err);
 }
 
 struct nfs_release_lockowner_data {
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1398,6 +1398,7 @@ static int nfs4_reclaim_locks(struct nfs
 	struct inode *inode = state->inode;
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct file_lock *fl;
+	struct nfs4_lock_state *lsp;
 	int status = 0;
 	struct file_lock_context *flctx = inode->i_flctx;
 	struct list_head *list;
@@ -1438,7 +1439,9 @@ restart:
 		case -NFS4ERR_DENIED:
 		case -NFS4ERR_RECLAIM_BAD:
 		case -NFS4ERR_RECLAIM_CONFLICT:
-			/* kill_proc(fl->fl_pid, SIGLOST, 1); */
+			lsp = fl->fl_u.nfs4_fl.owner;
+			if (lsp)
+				set_bit(NFS_LOCK_LOST, &lsp->ls_flags);
 			status = 0;
 		}
 		spin_lock(&flctx->flc_lock);