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[2003:dc:6f02:b200:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-482fbb2794dsm5480678f8f.25.2026.08.28.10.45.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Aug 2026 10:45:13 -0700 (PDT) From: Max Kellermann To: idryomov@gmail.com, amarkuze@redhat.com, xiubo.li@clyso.com, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Max Kellermann Subject: [PATCH v3 1/3] ceph/mds_client: pin sessions while checking a new MDS map Date: Fri, 28 Aug 2026 19:45:02 +0200 Message-ID: <20260828174504.1247038-2-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260828174504.1247038-1-max.kellermann@ionos.com> References: <20260828174504.1247038-1-max.kellermann@ionos.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit check_new_map() drops `mdsc->mutex` while it locks a session, prepares a reconnect, or cleans up caps. A concurrent teardown can unregister and release a session, invalidating check_new_map()'s local variable `s`. Fix this by taking a temporary session reference using __ceph_lookup_mds_session() instead of accessing the `sessions[]` array directly. Signed-off-by: Max Kellermann --- fs/ceph/mds_client.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 3c692ad02c85..160f23e2edd3 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -5798,9 +5798,9 @@ static void check_new_map(struct ceph_mds_client *mdsc, } for (i = 0; i < oldmap->possible_max_rank && i < mdsc->max_sessions; i++) { - if (!mdsc->sessions[i]) + s = __ceph_lookup_mds_session(mdsc, i); + if (!s) continue; - s = mdsc->sessions[i]; oldstate = ceph_mdsmap_get_state(oldmap, i); newstate = ceph_mdsmap_get_state(newmap, i); @@ -5813,7 +5813,6 @@ static void check_new_map(struct ceph_mds_client *mdsc, if (i >= newmap->possible_max_rank) { /* force close session for stopped mds */ - ceph_get_mds_session(s); __unregister_session(mdsc, s); __wake_requests(mdsc, &s->s_waiting); mutex_unlock(&mdsc->mutex); @@ -5841,6 +5840,7 @@ static void check_new_map(struct ceph_mds_client *mdsc, mutex_unlock(&s->s_mutex); s->s_state = CEPH_MDS_SESSION_RESTARTING; } else if (oldstate == newstate) { + ceph_put_mds_session(s); continue; /* nothing new with this mds */ } @@ -5878,6 +5878,7 @@ static void check_new_map(struct ceph_mds_client *mdsc, mutex_unlock(&s->s_mutex); wake_up_session_caps(s, RECONNECT); } + ceph_put_mds_session(s); } /* -- 2.47.3