linux-kernel - [PATCH 4.19 227/639] NFS: Fix a soft lockup in the delegation recovery code

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Message-Id: <20200124093115.321822499@linuxfoundation.org>
Date:   Fri, 24 Jan 2020 10:26:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 227/639] NFS: Fix a soft lockup in the delegation recovery code

From: Trond Myklebust <trond.myklebust@...merspace.com>

[ Upstream commit 6f9449be53f3ce383caed797708b332ede8d952c ]

Fix a soft lockup when NFS client delegation recovery is attempted
but the inode is in the process of being freed. When the
igrab(inode) call fails, and we have to restart the recovery process,
we need to ensure that we won't attempt to recover the same delegation
again.

Fixes: 45870d6909d5a ("NFSv4.1: Test delegation stateids when server...")
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/nfs/delegation.c | 20 ++++++++++++--------
 fs/nfs/delegation.h |  1 +
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 74ff459b75efa..b0c0c2fc2fbac 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -240,6 +240,8 @@ static struct inode *nfs_delegation_grab_inode(struct nfs_delegation *delegation
 	spin_lock(&delegation->lock);
 	if (delegation->inode != NULL)
 		inode = igrab(delegation->inode);
+	if (!inode)
+		set_bit(NFS_DELEGATION_INODE_FREEING, &delegation->flags);
 	spin_unlock(&delegation->lock);
 	return inode;
 }
@@ -955,10 +957,11 @@ restart:
 	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
 		list_for_each_entry_rcu(delegation, &server->delegations,
 								super_list) {
-			if (test_bit(NFS_DELEGATION_RETURNING,
-						&delegation->flags))
-				continue;
-			if (test_bit(NFS_DELEGATION_NEED_RECLAIM,
+			if (test_bit(NFS_DELEGATION_INODE_FREEING,
+						&delegation->flags) ||
+			    test_bit(NFS_DELEGATION_RETURNING,
+						&delegation->flags) ||
+			    test_bit(NFS_DELEGATION_NEED_RECLAIM,
 						&delegation->flags) == 0)
 				continue;
 			if (!nfs_sb_active(server->super))
@@ -1064,10 +1067,11 @@ restart:
 	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
 		list_for_each_entry_rcu(delegation, &server->delegations,
 								super_list) {
-			if (test_bit(NFS_DELEGATION_RETURNING,
-						&delegation->flags))
-				continue;
-			if (test_bit(NFS_DELEGATION_TEST_EXPIRED,
+			if (test_bit(NFS_DELEGATION_INODE_FREEING,
+						&delegation->flags) ||
+			    test_bit(NFS_DELEGATION_RETURNING,
+						&delegation->flags) ||
+			    test_bit(NFS_DELEGATION_TEST_EXPIRED,
 						&delegation->flags) == 0)
 				continue;
 			if (!nfs_sb_active(server->super))
diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h
index dd0f3eed3890d..f09b153ac82ff 100644
--- a/fs/nfs/delegation.h
+++ b/fs/nfs/delegation.h
@@ -34,6 +34,7 @@ enum {
 	NFS_DELEGATION_RETURNING,
 	NFS_DELEGATION_REVOKED,
 	NFS_DELEGATION_TEST_EXPIRED,
+	NFS_DELEGATION_INODE_FREEING,
 };
 
 int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred,
-- 
2.20.1