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squid: mds/quiesce: let clients keep their buffered writes for a quiesced file #57013

Merged
merged 2 commits into from
May 22, 2024
Merged

squid: mds/quiesce: let clients keep their buffered writes for a quiesced file #57013

merged 2 commits into from
May 22, 2024

Commits on Apr 21, 2024

  1. mds/quiesce: xlock the file to let clients keep their buffered writes 

    With the quiesce protocol taking a `rdlock` on the file,
it also revokes the `Fb` capability, which the clients can't release
until they are done flushing, and that may take up arbitrarily long,
evidently, more than 10 minutes.

We went for the rdlock to avoid affecting readonly clients,
but given the evidence above we should not optimize for those.
Ideally, we’d like to have a QUIESCE file lock mode where both rd
and buffer are allowed, but as of now it seems like our best
available option is to `xlock` the file which will let the writing
clients keep their buffers for the duration of the quiesce.

We can only afford this change for a `splitauth` config,
i.e. where we drop the lock immediately after all `Fw`s are revoked

Signed-off-by: Leonid Usov <leonid.usov@ibm.com>
(cherry picked from commit 8ac9842)
Fixes: https://tracker.ceph.com/issues/65556
Original-Issue: https://tracker.ceph.com/issues/65472
Original-PR: #56755
    @leonid-s-usov
    leonid-s-usov committed Apr 21, 2024
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  2. mds/quiesce: don't take mirrored cap-related locks on the replica 

    For every mirrored lock, the auth will message the replica to ensure
the replicated lock state. When we take x/rdlock on the auth, it will
ensure the LOCK_LOCK state on the replica, which has the file caps we
want for quiesce: CACHE and BUFFER.

It should be sufficient to only hold the quiesce local lock
on the replica side.

Signed-off-by: Leonid Usov <leonid.usov@ibm.com>
(cherry picked from commit eac482b)
Fixes: https://tracker.ceph.com/issues/65556
Original-Issue: https://tracker.ceph.com/issues/65472
Original-PR: #56755
    @leonid-s-usov
    leonid-s-usov committed Apr 21, 2024
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