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os/bluestore: fix deferred write deadlock, aio short return handling #17601

Merged
merged 3 commits into from Sep 10, 2017
Merged

os/bluestore: fix deferred write deadlock, aio short return handling #17601

merged 3 commits into from Sep 10, 2017

Commits on Sep 8, 2017

  1. os/bluestore: drop deferred_submit_lock 

    This lock serves no purpose.  It only protects the call to the aio_submit
on the OpSequencer running batch, but we are the only caller who will do
that submission, and a new batch won't be moved into place until ours is
completed and retired (by the completion for the aio we are queueing).

More importantly, this fixes a deadlock:

- thread A submits aio, but the queue is full, and blocks
- thread B blocks taking deferred_submit_lock while holding deferred_lock
- aio completion thread blocks trying to take deferred_lock, and thus
no further aios are drained.

Fixes: http://tracker.ceph.com/issues/21171
Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 7a5ef62)
    @liewegas
    liewegas committed Sep 8, 2017
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  2. os/bluestore: more deferred debugging 

    Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 11ac691)
    @liewegas
    liewegas committed Sep 8, 2017
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  3. os/bluestore/aio: handle short return from io_submit 

    io_submit may return a value less than nr, indicating that only some of
the provided iocbs were queued.  If that happens we should loop, not
return and silently drop those aios on the floor.

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit dc17dfd)
    @liewegas
    liewegas committed Sep 8, 2017
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