On Wed, 2021-08-18 at 09:31 +0800, xiubli@xxxxxxxxxx wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>
In case the export MDS is crashed just after the EImportStart journal
is flushed, so when a standby MDS takes over it and when replaying
the EImportStart journal the MDS will wait the client to reconnect,
but the client may never register/open the sessions yet.
We will try to reconnect that MDSes if they're in the export targets
and in RECONNECT state.
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
V3:
- switch to bitmap and on the stack
- put the ceph_put_mds_session() out of the mdsc->mutex lock scope
fs/ceph/mds_client.c | 55 +++++++++++++++++++++++++++++++++++++++++++-
fs/ceph/mdsmap.c | 10 +++++---
2 files changed, 61 insertions(+), 4 deletions(-)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index e49dbeb6c06f..c2fca06b09a0 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -11,6 +11,7 @@
#include <linux/ratelimit.h>
#include <linux/bits.h>
#include <linux/ktime.h>
+#include <linux/bitmap.h>
#include "super.h"
#include "mds_client.h"
@@ -4197,13 +4198,19 @@ static void check_new_map(struct ceph_mds_client *mdsc,
struct ceph_mdsmap *newmap,
struct ceph_mdsmap *oldmap)
{
- int i;
+ int i, err;
int oldstate, newstate;
struct ceph_mds_session *s;
+ unsigned long targets[DIV_ROUND_UP(CEPH_MAX_MDS, sizeof(unsigned long))] = {0};
dout("check_new_map new %u old %u\n",
newmap->m_epoch, oldmap->m_epoch);
+ if (newmap->m_info) {
+ for (i = 0; i < newmap->m_info->num_export_targets; i++)
+ set_bit(newmap->m_info->export_targets[i], targets);
+ }
+
I wasn't aware you could exceed the size of the first unsigned long in
the array with the atomic bitops handlers. Looking at the helpers
themselves though, I don't see why this wouldn't work. Ok!
for (i = 0; i < oldmap->possible_max_rank && i < mdsc->max_sessions; i++) {
if (!mdsc->sessions[i])
continue;
@@ -4257,6 +4264,7 @@ static void check_new_map(struct ceph_mds_client *mdsc,
if (s->s_state == CEPH_MDS_SESSION_RESTARTING &&
newstate >= CEPH_MDS_STATE_RECONNECT) {
mutex_unlock(&mdsc->mutex);
+ clear_bit(i, targets);
send_mds_reconnect(mdsc, s);
mutex_lock(&mdsc->mutex);
}
@@ -4279,6 +4287,51 @@ static void check_new_map(struct ceph_mds_client *mdsc,
}
}
+ /*
+ * Only open and reconnect sessions that don't exist yet.
+ */
+ for (i = 0; i < newmap->possible_max_rank; i++) {
+ /*
+ * In case the import MDS is crashed just after
+ * the EImportStart journal is flushed, so when
+ * a standby MDS takes over it and is replaying
+ * the EImportStart journal the new MDS daemon
+ * will wait the client to reconnect it, but the
+ * client may never register/open the session yet.
+ *
+ * Will try to reconnect that MDS daemon if the
+ * rank number is in the export targets array and
+ * is the up:reconnect state.
+ */
+ newstate = ceph_mdsmap_get_state(newmap, i);
+ if (!test_bit(i, targets) || newstate != CEPH_MDS_STATE_RECONNECT)
+ continue;
+
+ /*
+ * The session maybe registered and opened by some
+ * requests which were choosing random MDSes during
+ * the mdsc->mutex's unlock/lock gap below in rare
+ * case. But the related MDS daemon will just queue
+ * that requests and be still waiting for the client's
+ * reconnection request in up:reconnect state.
+ */
+ s = __ceph_lookup_mds_session(mdsc, i);
+ if (likely(!s)) {
+ s = __open_export_target_session(mdsc, i);
+ if (IS_ERR(s)) {
+ err = PTR_ERR(s);
+ pr_err("failed to open export target session, err %d\n",
+ err);
+ continue;
+ }
+ }
+ dout("send reconnect to export target mds.%d\n", i);
+ mutex_unlock(&mdsc->mutex);
+ send_mds_reconnect(mdsc, s);
+ ceph_put_mds_session(s);
+ mutex_lock(&mdsc->mutex);
+ }
+
for (i = 0; i < newmap->possible_max_rank && i < mdsc->max_sessions; i++) {
s = mdsc->sessions[i];
if (!s)
diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
index 3c444b9cb17b..d995cb02d30c 100644
--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -122,6 +122,7 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
int err;
u8 mdsmap_v;
u16 mdsmap_ev;
+ u32 target;
m = kzalloc(sizeof(*m), GFP_NOFS);
if (!m)
@@ -260,9 +261,12 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
sizeof(u32), GFP_NOFS);
if (!info->export_targets)
goto nomem;
- for (j = 0; j < num_export_targets; j++)
- info->export_targets[j] =
- ceph_decode_32(&pexport_targets);
+ for (j = 0; j < num_export_targets; j++) {
+ target = ceph_decode_32(&pexport_targets);
+ if (target >= m->possible_max_rank)
+ goto corrupt;
+ info->export_targets[j] = target;
+ }
} else {
info->export_targets = NULL;
}
Looks good. Merged into testing. I also reworded the changelog for
(hopefully) better clarity. Xiubo, let me know if I didn't get the
description right.
