Some messages sent by the MDS entail a session sequence number
increment, and the MDS will drop certain types of requests on the floor
when the sequence numbers don't match.
In particular, a REQUEST_CLOSE message can cross with one of the
sequence morphing messages from the MDS which can cause the client to
stall, waiting for a response that will never come.
Originally, this meant an up to 5s delay before the recurring workqueue
job kicked in and resent the request, but a recent change made it so
that the client would never resend, causing a 60s stall unmounting and
sometimes a blockisting event.
Add a new helper for incrementing the session sequence and then testing
to see whether a REQUEST_CLOSE needs to be resent, and move the handling
of CEPH_MDS_SESSION_CLOSING into that function. Change all of the
bare sequence counter increments to use the new helper.
Reorganize check_session_state with a switch statement. It should no
longer be called when the session is CLOSING, so throw a warning if it
ever is (but still handle that case sanely).
URL: https://tracker.ceph.com/issues/47563
Fixes: fa9967734227 ("ceph: fix potential mdsc use-after-free crash")
Reported-by: Patrick Donnelly <pdonnell@xxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/ceph/caps.c | 2 +-
fs/ceph/mds_client.c | 51 ++++++++++++++++++++++++++++++--------------
fs/ceph/mds_client.h | 1 +
fs/ceph/quota.c | 2 +-
fs/ceph/snap.c | 2 +-
5 files changed, 39 insertions(+), 19 deletions(-)
v3: reorganize check_session_state with switch statement. Don't attempt
to reconnect in there, but do throw a warning if it's called while
the session is CLOSING.
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index c00abd7eefc1..ba0e4f44862c 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -4071,7 +4071,7 @@ void ceph_handle_caps(struct ceph_mds_session *session,
vino.snap, inode);
mutex_lock(&session->s_mutex);
- session->s_seq++;
+ inc_session_sequence(session);
dout(" mds%d seq %lld cap seq %u\n", session->s_mds, session->s_seq,
(unsigned)seq);
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 0190555b1f9e..00c0dc33f92e 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -4237,7 +4237,7 @@ static void handle_lease(struct ceph_mds_client *mdsc,
dname.len, dname.name);
mutex_lock(&session->s_mutex);
- session->s_seq++;
+ inc_session_sequence(session);
if (!inode) {
dout("handle_lease no inode %llx\n", vino.ino);
@@ -4386,28 +4386,47 @@ static void maybe_recover_session(struct ceph_mds_client *mdsc)
bool check_session_state(struct ceph_mds_session *s)
{
- if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
- dout("resending session close request for mds%d\n",
- s->s_mds);
- request_close_session(s);
- return false;
- }
- if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
- if (s->s_state == CEPH_MDS_SESSION_OPEN) {
+
+ switch (s->s_state) {
+ case CEPH_MDS_SESSION_OPEN:
+ if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
s->s_state = CEPH_MDS_SESSION_HUNG;
pr_info("mds%d hung\n", s->s_mds);
}
- }
- if (s->s_state == CEPH_MDS_SESSION_NEW ||
- s->s_state == CEPH_MDS_SESSION_RESTARTING ||
- s->s_state == CEPH_MDS_SESSION_CLOSED ||
- s->s_state == CEPH_MDS_SESSION_REJECTED)
- /* this mds is failed or recovering, just wait */
+ break;
+ case CEPH_MDS_SESSION_CLOSING:
+ /* Should never reach this when we're unmounting */
+ WARN_ON_ONCE(true);
+ fallthrough;
+ case CEPH_MDS_SESSION_NEW:
+ case CEPH_MDS_SESSION_RESTARTING:
+ case CEPH_MDS_SESSION_CLOSED:
+ case CEPH_MDS_SESSION_REJECTED:
return false;
-
+ }
return true;
}
+/*
+ * If the sequence is incremented while we're waiting on a REQUEST_CLOSE reply,
+ * then we need to retransmit that request.
+ */
+void inc_session_sequence(struct ceph_mds_session *s)
+{
+ lockdep_assert_held(&s->s_mutex);
+
+ s->s_seq++;
+
+ if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
+ int ret;
+
+ dout("resending session close request for mds%d\n", s->s_mds);
+ ret = request_close_session(s);
+ if (ret < 0)
+ pr_err("ceph: Unable to close session to mds %d: %d\n", s->s_mds, ret);
+ }
+}
+
/*
* delayed work -- periodically trim expired leases, renew caps with mds
*/
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index cbf8af437140..f5adbebcb38e 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -480,6 +480,7 @@ struct ceph_mds_client {
extern const char *ceph_mds_op_name(int op);
extern bool check_session_state(struct ceph_mds_session *s);
+void inc_session_sequence(struct ceph_mds_session *s);
extern struct ceph_mds_session *
__ceph_lookup_mds_session(struct ceph_mds_client *, int mds);
diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
index 83cb4f26b689..9b785f11e95a 100644
--- a/fs/ceph/quota.c
+++ b/fs/ceph/quota.c
@@ -53,7 +53,7 @@ void ceph_handle_quota(struct ceph_mds_client *mdsc,
/* increment msg sequence number */
mutex_lock(&session->s_mutex);
- session->s_seq++;
+ inc_session_sequence(session);
mutex_unlock(&session->s_mutex);
/* lookup inode */
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index 0da39c16dab4..b611f829cb61 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -873,7 +873,7 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
ceph_snap_op_name(op), split, trace_len);
mutex_lock(&session->s_mutex);
- session->s_seq++;
+ inc_session_sequence(session);
mutex_unlock(&session->s_mutex);
down_write(&mdsc->snap_rwsem);
