From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
state_lock is a heavily contended global lock. We don't want to grab
that while simultaneously holding the inode->i_lock. Avoid doing that in
the delegation break callback by ensuring that we add/remove the
dl_perfile under the inode->i_lock.
This however, can cause an ABBA deadlock between the state_lock and the
i_lock. Work around that by doing the list manipulation in the delegation
recall from the workqueue context prior to starting the rpc call.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
---
fs/nfsd/nfs4callback.c | 18 ++++++++++++++++--
fs/nfsd/nfs4state.c | 41 +++++++++++++++++++++++++++--------------
fs/nfsd/state.h | 1 +
3 files changed, 44 insertions(+), 16 deletions(-)
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 2c73cae9899d..3d67bbf26cee 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1011,9 +1011,8 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
run_nfsd4_cb(cb);
}
-static void nfsd4_do_callback_rpc(struct work_struct *w)
+static void nfsd4_run_callback_rpc(struct nfsd4_callback *cb)
{
- struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, cb_work);
struct nfs4_client *clp = cb->cb_clp;
struct rpc_clnt *clnt;
@@ -1031,11 +1030,25 @@ static void nfsd4_do_callback_rpc(struct work_struct *w)
cb->cb_ops, cb);
}
+static void nfsd4_do_callback_rpc(struct work_struct *w)
+{
+ struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, cb_work);
+ nfsd4_run_callback_rpc(cb);
+}
+
void nfsd4_init_callback(struct nfsd4_callback *cb)
{
INIT_WORK(&cb->cb_work, nfsd4_do_callback_rpc);
}
+static void nfsd4_do_cb_recall(struct work_struct *w)
+{
+ struct nfsd4_callback *cb = container_of(w, struct nfsd4_callback, cb_work);
+
+ nfsd4_prepare_cb_recall(cb->cb_op);
+ nfsd4_run_callback_rpc(cb);
+}
+
void nfsd4_cb_recall(struct nfs4_delegation *dp)
{
struct nfsd4_callback *cb = &dp->dl_recall;
@@ -1052,6 +1065,7 @@ void nfsd4_cb_recall(struct nfs4_delegation *dp)
INIT_LIST_HEAD(&cb->cb_per_client);
cb->cb_done = true;
+ INIT_WORK(&cb->cb_work, nfsd4_do_cb_recall);
run_nfsd4_cb(&dp->dl_recall);
}
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 553c2d6d48dc..c249c5261640 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -438,7 +438,9 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
lockdep_assert_held(&state_lock);
dp->dl_stid.sc_type = NFS4_DELEG_STID;
+ spin_lock(&fp->fi_inode->i_lock);
list_add(&dp->dl_perfile, &fp->fi_delegations);
+ spin_unlock(&fp->fi_inode->i_lock);
list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
}
@@ -446,14 +448,20 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
static void
unhash_delegation(struct nfs4_delegation *dp)
{
+ struct nfs4_file *fp = dp->dl_file;
+
spin_lock(&state_lock);
list_del_init(&dp->dl_perclnt);
- list_del_init(&dp->dl_perfile);
list_del_init(&dp->dl_recall_lru);
+ if (!list_empty(&dp->dl_perfile)) {
+ spin_lock(&fp->fi_inode->i_lock);
+ list_del_init(&dp->dl_perfile);
+ spin_unlock(&fp->fi_inode->i_lock);
+ }
spin_unlock(&state_lock);
- if (dp->dl_file) {
- nfs4_put_deleg_lease(dp->dl_file);
- put_nfs4_file(dp->dl_file);
+ if (fp) {
+ nfs4_put_deleg_lease(fp);
+ put_nfs4_file(fp);
dp->dl_file = NULL;
}
}
@@ -2766,24 +2774,31 @@ out:
return ret;
}
-static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
+void nfsd4_prepare_cb_recall(struct nfs4_delegation *dp)
{
struct nfs4_client *clp = dp->dl_stid.sc_client;
struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
- lockdep_assert_held(&state_lock);
+ /*
+ * We can't do this in nfsd_break_deleg_cb because it is
+ * already holding inode->i_lock
+ */
+ spin_lock(&state_lock);
+ if (list_empty(&dp->dl_recall_lru)) {
+ dp->dl_time = get_seconds();
+ list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru);
+ }
+ spin_unlock(&state_lock);
+}
+
+static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
+{
/* We're assuming the state code never drops its reference
* without first removing the lease. Since we're in this lease
* callback (and since the lease code is serialized by the kernel
* lock) we know the server hasn't removed the lease yet, we know
* it's safe to take a reference: */
atomic_inc(&dp->dl_count);
-
- list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru);
-
- /* Only place dl_time is set; protected by i_lock: */
- dp->dl_time = get_seconds();
-
nfsd4_cb_recall(dp);
}
@@ -2808,11 +2823,9 @@ static void nfsd_break_deleg_cb(struct file_lock *fl)
*/
fl->fl_break_time = 0;
- spin_lock(&state_lock);
fp->fi_had_conflict = true;
list_for_each_entry(dp, &fp->fi_delegations, dl_perfile)
nfsd_break_one_deleg(dp);
- spin_unlock(&state_lock);
}
static
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 374c66283ac5..aacccb2a476c 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -472,6 +472,7 @@ extern void nfsd4_cb_recall(struct nfs4_delegation *dp);
extern int nfsd4_create_callback_queue(void);
extern void nfsd4_destroy_callback_queue(void);
extern void nfsd4_shutdown_callback(struct nfs4_client *);
+extern void nfsd4_prepare_cb_recall(struct nfs4_delegation *dp);
extern void nfs4_put_delegation(struct nfs4_delegation *dp);
extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(const char *name,
struct nfsd_net *nn);
--
1.9.3
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