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author | Xiubo Li <xiubli@redhat.com> | 2022-02-19 09:28:33 +0300 |
---|---|---|
committer | Ilya Dryomov <idryomov@gmail.com> | 2022-03-01 20:26:37 +0300 |
commit | 2e586641c950e7f3e7e008404bd783a466b9b590 (patch) | |
tree | 7883792cbc526a378942b51ea7d768194c98bf56 /fs | |
parent | 2941bf53f59c5fb4def7e5883cb452ae7b2ee304 (diff) | |
download | linux-2e586641c950e7f3e7e008404bd783a466b9b590.tar.xz |
ceph: do not update snapshot context when there is no new snapshot
We will only track the uppest parent snapshot realm from which we
need to rebuild the snapshot contexts _downward_ in hierarchy. For
all the others having no new snapshot we will do nothing.
This fix will avoid calling ceph_queue_cap_snap() on some inodes
inappropriately. For example, with the code in mainline, suppose there
are 2 directory hierarchies (with 6 directories total), like this:
/dir_X1/dir_X2/dir_X3/
/dir_Y1/dir_Y2/dir_Y3/
Firstly, make a snapshot under /dir_X1/dir_X2/.snap/snap_X2, then make a
root snapshot under /.snap/root_snap. Every time we make snapshots under
/dir_Y1/..., the kclient will always try to rebuild the snap context for
snap_X2 realm and finally will always try to queue cap snaps for dir_Y2
and dir_Y3, which makes no sense.
That's because the snap_X2's seq is 2 and root_snap's seq is 3. So when
creating a new snapshot under /dir_Y1/... the new seq will be 4, and
the mds will send the kclient a snapshot backtrace in _downward_
order: seqs 4, 3.
When ceph_update_snap_trace() is called, it will always rebuild the from
the last realm, that's the root_snap. So later when rebuilding the snap
context, the current logic will always cause it to rebuild the snap_X2
realm and then try to queue cap snaps for all the inodes related in that
realm, even though it's not necessary.
This is accompanied by a lot of these sorts of dout messages:
"ceph: queue_cap_snap 00000000a42b796b nothing dirty|writing"
Fix the logic to avoid this situation.
Also, the 'invalidate' word is not precise here. In actuality, it will
cause a rebuild of the existing snapshot contexts or just build
non-existent ones. Rename it to 'rebuild_snapcs'.
URL: https://tracker.ceph.com/issues/44100
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/ceph/snap.c | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index bc5ec72d958c..5fd79ae96f34 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -708,7 +708,8 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc, __le64 *prior_parent_snaps; /* encoded */ struct ceph_snap_realm *realm = NULL; struct ceph_snap_realm *first_realm = NULL; - int invalidate = 0; + struct ceph_snap_realm *realm_to_rebuild = NULL; + int rebuild_snapcs; int err = -ENOMEM; LIST_HEAD(dirty_realms); @@ -716,6 +717,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc, dout("update_snap_trace deletion=%d\n", deletion); more: + rebuild_snapcs = 0; ceph_decode_need(&p, e, sizeof(*ri), bad); ri = p; p += sizeof(*ri); @@ -739,7 +741,7 @@ more: err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent)); if (err < 0) goto fail; - invalidate += err; + rebuild_snapcs += err; if (le64_to_cpu(ri->seq) > realm->seq) { dout("update_snap_trace updating %llx %p %lld -> %lld\n", @@ -764,22 +766,30 @@ more: if (realm->seq > mdsc->last_snap_seq) mdsc->last_snap_seq = realm->seq; - invalidate = 1; + rebuild_snapcs = 1; } else if (!realm->cached_context) { dout("update_snap_trace %llx %p seq %lld new\n", realm->ino, realm, realm->seq); - invalidate = 1; + rebuild_snapcs = 1; } else { dout("update_snap_trace %llx %p seq %lld unchanged\n", realm->ino, realm, realm->seq); } - dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino, - realm, invalidate, p, e); + dout("done with %llx %p, rebuild_snapcs=%d, %p %p\n", realm->ino, + realm, rebuild_snapcs, p, e); - /* invalidate when we reach the _end_ (root) of the trace */ - if (invalidate && p >= e) - rebuild_snap_realms(realm, &dirty_realms); + /* + * this will always track the uppest parent realm from which + * we need to rebuild the snapshot contexts _downward_ in + * hierarchy. + */ + if (rebuild_snapcs) + realm_to_rebuild = realm; + + /* rebuild_snapcs when we reach the _end_ (root) of the trace */ + if (realm_to_rebuild && p >= e) + rebuild_snap_realms(realm_to_rebuild, &dirty_realms); if (!first_realm) first_realm = realm; |