NFSv4.1 Fix a pNFS session draining deadlock
On a CB_RECALL the callback service thread flushes the inode using
filemap_flush prior to scheduling the state manager thread to return the
delegation. When pNFS is used and I/O has not yet gone to the data server
servicing the inode, a LAYOUTGET can preceed the I/O. Unlike the async
filemap_flush call, the LAYOUTGET must proceed to completion.
If the state manager starts to recover data while the inode flush is sending
the LAYOUTGET, a deadlock occurs as the callback service thread holds the
single callback session slot until the flushing is done which blocks the state
manager thread, and the state manager thread has set the session draining bit
which puts the inode flush LAYOUTGET RPC to sleep on the forechannel slot
table waitq.
Separate the draining of the back channel from the draining of the fore channel
by moving the NFS4_SESSION_DRAINING bit from session scope into the fore
and back slot tables. Drain the back channel first allowing the LAYOUTGET
call to proceed (and fail) so the callback service thread frees the callback
slot. Then proceed with draining the forechannel.
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 300d17d..1fab140 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -241,7 +241,7 @@
if (ses == NULL)
return;
tbl = &ses->fc_slot_table;
- if (test_and_clear_bit(NFS4_SESSION_DRAINING, &ses->session_state)) {
+ if (test_and_clear_bit(NFS4_SLOT_TBL_DRAINING, &tbl->slot_tbl_state)) {
spin_lock(&tbl->slot_tbl_lock);
nfs41_wake_slot_table(tbl);
spin_unlock(&tbl->slot_tbl_lock);
@@ -251,15 +251,15 @@
/*
* Signal state manager thread if session fore channel is drained
*/
-void nfs4_session_drain_complete(struct nfs4_session *session,
- struct nfs4_slot_table *tbl)
+void nfs4_slot_tbl_drain_complete(struct nfs4_slot_table *tbl)
{
- if (nfs4_session_draining(session))
+ if (nfs4_slot_tbl_draining(tbl))
complete(&tbl->complete);
}
-static int nfs4_wait_on_slot_tbl(struct nfs4_slot_table *tbl)
+static int nfs4_drain_slot_tbl(struct nfs4_slot_table *tbl)
{
+ set_bit(NFS4_SLOT_TBL_DRAINING, &tbl->slot_tbl_state);
spin_lock(&tbl->slot_tbl_lock);
if (tbl->highest_used_slotid != NFS4_NO_SLOT) {
INIT_COMPLETION(tbl->complete);
@@ -275,13 +275,12 @@
struct nfs4_session *ses = clp->cl_session;
int ret = 0;
- set_bit(NFS4_SESSION_DRAINING, &ses->session_state);
/* back channel */
- ret = nfs4_wait_on_slot_tbl(&ses->bc_slot_table);
+ ret = nfs4_drain_slot_tbl(&ses->bc_slot_table);
if (ret)
return ret;
/* fore channel */
- return nfs4_wait_on_slot_tbl(&ses->fc_slot_table);
+ return nfs4_drain_slot_tbl(&ses->fc_slot_table);
}
static void nfs41_finish_session_reset(struct nfs_client *clp)