On 07/12/2022 18:59, Ilya Dryomov wrote:
On Tue, Dec 6, 2022 at 1:59 PM <xiubli@xxxxxxxxxx> wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>
When received corrupted snap trace we don't know what exactly has
happened in MDS side. And we shouldn't continue writing to OSD,
which may corrupt the snapshot contents.
Just try to blocklist this client and If fails we need to crash the
client instead of leaving it writeable to OSDs.
Cc: stable@xxxxxxxxxxxxxxx
URL: https://tracker.ceph.com/issues/57686
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
Thanks Aaron's feedback.
V3:
- Fixed ERROR: spaces required around that ':' (ctx:VxW)
V2:
- Switched to WARN() to taint the Linux kernel.
fs/ceph/mds_client.c | 3 ++-
fs/ceph/mds_client.h | 1 +
fs/ceph/snap.c | 25 +++++++++++++++++++++++++
3 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index cbbaf334b6b8..59094944af28 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -5648,7 +5648,8 @@ static void mds_peer_reset(struct ceph_connection *con)
struct ceph_mds_client *mdsc = s->s_mdsc;
pr_warn("mds%d closed our session\n", s->s_mds);
- send_mds_reconnect(mdsc, s);
+ if (!mdsc->no_reconnect)
+ send_mds_reconnect(mdsc, s);
}
static void mds_dispatch(struct ceph_connection *con, struct ceph_msg *msg)
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index 728b7d72bf76..8e8f0447c0ad 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -413,6 +413,7 @@ struct ceph_mds_client {
atomic_t num_sessions;
int max_sessions; /* len of sessions array */
int stopping; /* true if shutting down */
+ int no_reconnect; /* true if snap trace is corrupted */
atomic64_t quotarealms_count; /* # realms with quota */
/*
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index c1c452afa84d..023852b7c527 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -767,8 +767,10 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm;
struct ceph_snap_realm *first_realm = NULL;
struct ceph_snap_realm *realm_to_rebuild = NULL;
+ struct ceph_client *client = mdsc->fsc->client;
int rebuild_snapcs;
int err = -ENOMEM;
+ int ret;
LIST_HEAD(dirty_realms);
lockdep_assert_held_write(&mdsc->snap_rwsem);
@@ -885,6 +887,29 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
if (first_realm)
ceph_put_snap_realm(mdsc, first_realm);
pr_err("%s error %d\n", __func__, err);
+
+ /*
+ * When receiving a corrupted snap trace we don't know what
+ * exactly has happened in MDS side. And we shouldn't continue
+ * writing to OSD, which may corrupt the snapshot contents.
+ *
+ * Just try to blocklist this kclient and if it fails we need
+ * to crash the kclient instead of leaving it writeable.
Hi Xiubo,
I'm not sure I understand this "let's blocklist ourselves" concept.
If the kernel client shouldn't continue writing to OSDs in this case,
why not just stop issuing writes -- perhaps initiating some equivalent
of a read-only remount like many local filesystems would do on I/O
errors (e.g. errors=remount-ro mode)?
The following patch seems working. Let me do more test to make sure
there is not further crash.
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index c1c452afa84d..cd487f8a4cb5 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -767,6 +767,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
struct ceph_snap_realm *realm;
struct ceph_snap_realm *first_realm = NULL;
struct ceph_snap_realm *realm_to_rebuild = NULL;
+ struct super_block *sb = mdsc->fsc->sb;
int rebuild_snapcs;
int err = -ENOMEM;
LIST_HEAD(dirty_realms);
@@ -885,6 +886,9 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
if (first_realm)
ceph_put_snap_realm(mdsc, first_realm);
pr_err("%s error %d\n", __func__, err);
+ pr_err("Remounting filesystem read-only\n");
+ sb->s_flags |= SB_RDONLY;
+
return err;
}
Or, perhaps, all in-memory snap contexts could somehow be invalidated
in this case, making writes fail naturally -- on the client side,
without actually being sent to OSDs just to be nixed by the blocklist
hammer.
But further, what makes a failure to decode a snap trace special?
AFAIK we don't do anything close to this for any other decoding
failure. Wouldn't "when received corrupted XYZ we don't know what
exactly has happened in MDS side" argument apply to pretty much all
decoding failures?
+ *
+ * Then this kclient must be remounted to continue after the
+ * corrupted metadata fixed in the MDS side.
+ */
+ mdsc->no_reconnect = 1;
+ ret = ceph_monc_blocklist_add(&client->monc, &client->msgr.inst.addr);
+ if (ret) {
+ pr_err("%s blocklist of %s failed: %d", __func__,
+ ceph_pr_addr(&client->msgr.inst.addr), ret);
+ BUG();
... and this is a rough equivalent of errors=panic mode.
Is there a corresponding userspace client PR that can be referenced?
This needs additional background and justification IMO.
Thanks,
Ilya
