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ceph: check session state after bumping session->s_seq

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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).

[ idryomov: whitespace, pr_err() call fixup ]

URL: https://tracker.ceph.com/issues/47563
Fixes: fa99677342 ("ceph: fix potential mdsc use-after-free crash")
Reported-by: Patrick Donnelly <pdonnell@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Jeff Layton 2020-10-12 09:39:06 -04:00 committed by Ilya Dryomov
parent 3cea11cd5e
commit 62575e270f
5 changed files with 39 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/ceph/caps.c
View File

@ -4074,7 +4074,7 @@ 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);

50
fs/ceph/mds_client.c
View File

@ -4231,7 +4231,7 @@ 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);
@ -4385,28 +4385,48 @@ 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("unable to close session to mds%d: %d\n",
s->s_mds, ret);
}
}
/*
* delayed work -- periodically trim expired leases, renew caps with mds
*/

1
fs/ceph/mds_client.h
View File

@ -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);

2
fs/ceph/quota.c
View File

@ -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 */

2
fs/ceph/snap.c
View File

@ -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);