[Virtio-fs] [PATCH 0/5] virtiofs: Fix couple of deadlocks
Vivek Goyal
vgoyal at redhat.com
Tue Oct 15 17:46:21 UTC 2019
Hi,
We have couple of places which can result in deadlock. This patch series
fixes these.
We can be called with fc->bg_lock (for background requests) while
submitting a request. This leads to two constraints.
- We can't end requests in submitter's context and call fuse_end_request()
as it tries to take fc->bg_lock as well. So queue these requests on a
list and use a worker to end these requests.
- If virtqueue is full, we can wait with fc->bg_lock held for queue to
have space. Worker which is completing the request gets blocked on
fc->bg_lock as well. And that means requests are not completing, that
means descriptors are not being freed and that means submitter can't
make progress. Deadlock.
Fix this by punting the requests to a list and retry submission later
with the help of a worker.
Thanks
Vivek
Vivek Goyal (5):
virtiofs: Do not end request in submission context
virtiofs: No need to check fpq->connected state
virtiofs: Set FR_SENT flag only after request has been sent
virtiofs: Count pending forgets as in_flight forgets
virtiofs: Retry request submission from worker context
fs/fuse/virtio_fs.c | 165 +++++++++++++++++++++++++++++---------------
1 file changed, 111 insertions(+), 54 deletions(-)
--
2.20.1
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