On Tue, Mar 31, 2020 at 06:52:23AM -0400, Jeff Layton wrote: > 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> Feel free to add my Reviewed-by (and also tested). Also, it may be worth adding a stable tag for this patch, although it would require some massaging to use __send_cap instead of __prep_cap. Cheers, -- Luis > --- > 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 >
