NFSv4: Fix races between nfs_remove_bad_delegation() and delegation return

Any attempt to call nfs_remove_bad_delegation() while a delegation is being
returned is currently a no-op. This means that we can end up looping
forever in nfs_end_delegation_return() if something causes the delegation
to be revoked.
This patch adds a mechanism whereby the state recovery code can communicate
to the delegation return code that the delegation is no longer valid and
that it should not be used when reclaiming state.
It also changes the return value for nfs4_handle_delegation_recall_error()
to ensure that nfs_end_delegation_return() does not reattempt the lock
reclaim before state recovery is done.

http://lkml.kernel.org/r/CAN-5tyHwG=Cn2Q9KsHWadewjpTTy_K26ee+UnSvHvG4192p-Xw@mail.gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 5853f53db73246df670ce9daedb73e10d62d2da3..e5f473d13e249b6804daa6a7c7e3d423df80c8e2 100644 (file)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -193,7 +193,11 @@ static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *
 {
        int res = 0;
 
-       res = nfs4_proc_delegreturn(inode, delegation->cred, &delegation->stateid, issync);
+       if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
+               res = nfs4_proc_delegreturn(inode,
+                               delegation->cred,
+                               &delegation->stateid,
+                               issync);
        nfs_free_delegation(delegation);
        return res;
 }
@@ -380,11 +384,13 @@ static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation
 {
        struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
        struct nfs_inode *nfsi = NFS_I(inode);
-       int err;
+       int err = 0;
 
        if (delegation == NULL)
                return 0;
        do {
+               if (test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
+                       break;
                err = nfs_delegation_claim_opens(inode, &delegation->stateid);
                if (!issync || err != -EAGAIN)
                        break;
@@ -605,10 +611,23 @@ static void nfs_client_mark_return_unused_delegation_types(struct nfs_client *cl
        rcu_read_unlock();
 }
 
+static void nfs_revoke_delegation(struct inode *inode)
+{
+       struct nfs_delegation *delegation;
+       rcu_read_lock();
+       delegation = rcu_dereference(NFS_I(inode)->delegation);
+       if (delegation != NULL) {
+               set_bit(NFS_DELEGATION_REVOKED, &delegation->flags);
+               nfs_mark_return_delegation(NFS_SERVER(inode), delegation);
+       }
+       rcu_read_unlock();
+}
+
 void nfs_remove_bad_delegation(struct inode *inode)
 {
        struct nfs_delegation *delegation;
 
+       nfs_revoke_delegation(inode);
        delegation = nfs_inode_detach_delegation(inode);
        if (delegation) {
                nfs_inode_find_state_and_recover(inode, &delegation->stateid);

diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h
index 5c1cce39297f68fb178b4a125a83001aeac4afde..e3c20a3ccc937453b678e9bb02d1a46827f11be0 100644 (file)
--- a/fs/nfs/delegation.h
+++ b/fs/nfs/delegation.h
@@ -31,6 +31,7 @@ enum {
        NFS_DELEGATION_RETURN_IF_CLOSED,
        NFS_DELEGATION_REFERENCED,
        NFS_DELEGATION_RETURNING,
+       NFS_DELEGATION_REVOKED,
 };
 
 int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res);

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3b98fe752ef8c611670f382d44dfe56c65e4fc7d..4b7166f4e1cf762c4d5e0da2727ca6d7cc43356e 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1654,7 +1654,7 @@ static int nfs4_handle_delegation_recall_error(struct nfs_server *server, struct
                        nfs_inode_find_state_and_recover(state->inode,
                                        stateid);
                        nfs4_schedule_stateid_recovery(server, state);
-                       return 0;
+                       return -EAGAIN;
                case -NFS4ERR_DELAY:
                case -NFS4ERR_GRACE:
                        set_bit(NFS_DELEGATED_STATE, &state->flags);