Jan noticed some long stalls when flushing caps using sync() after
doing small file creates. For instance, running this:
$ time for i in $(seq -w 11 30); do echo "Hello World" > hello-$i.txt; sync -f ./hello-$i.txt; done
Could take more than 90s in some cases. The sync() will flush out caps,
but doesn't tell the MDS that it's waiting synchronously on the
replies.
When ceph_check_caps finds that CHECK_CAPS_FLUSH is set, then set the
CEPH_CLIENT_CAPS_SYNC bit in the cap update request. This clues the MDS
into that fact and it can then expedite the reply.
URL: https://tracker.ceph.com/issues/44744
Reported-and-Tested-by: Jan Fajerski <jfajerski@xxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/ceph/caps.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 61808793e0c0..6403178f2376 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2111,8 +2111,11 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,
mds = cap->mds; /* remember mds, so we don't repeat */
- __prep_cap(&arg, cap, CEPH_CAP_OP_UPDATE, 0, cap_used, want,
- retain, flushing, flush_tid, oldest_flush_tid);
+ __prep_cap(&arg, cap, CEPH_CAP_OP_UPDATE,
+ (flags & CHECK_CAPS_FLUSH) ?
+ CEPH_CLIENT_CAPS_SYNC : 0,
+ cap_used, want, retain, flushing, flush_tid,
+ oldest_flush_tid);
spin_unlock(&ci->i_ceph_lock);
__send_cap(mdsc, &arg, ci);
--
2.25.1
