Hi, As of now we do not support blocking remote posix locks with virtiofs. Well fuse client does not care but server returns -EOPNOTSUPP. There are couple of reasons to not support it yet. - If virtiofsd is single threaded or does not have a thread pool just to handle requests which can block for a long time, virtiofsd will stop processing new requests and virtiofs will come to a halt. To the extent that further unlock request will not make progress and deadlock will result. This can be taken care of by creating a custom thread pool in virtiofsd just to hanlde lock requests. - If client sends a blocking lock request and blocks, then it will consume descriptors in vring. If enough processes block, it is possible that vring does not have capacity to send more requests till some response comes back and descriptors are free. This can also lead to deadlock where an unlock request can't be sent to virtiofsd now. Also this will stop virtiofs operation as well as new filesystem requests can't be sent. To avoid this issue, idea was suggested thatn when a blocking lock request is sent by client, do not block it. Immediately send a reply saying client process should wait for a notification which will let it know once lock is available. This will make sure descriptors in virtqueue are not kept busy while we are waiting for lock and future unlock and other file system requests can continue to make progress. This first requires a notion of notification queue and virtiosfd being able to send notifications to client. This patch series implements that as well. As of now only one notification type has been implemented but now infrastructure is in place and other use cases should be easily add more type of notifications as need be. We don't yet have the capability to interrupt the process which is waiting for the posix lock. And reason for that is that virtiofs does not support capability to interrupt yet. That's a TODO item for later. Please have a look. Thanks Vivek Vivek Goyal (8): virtiofs: Disable interrupt requests properly virtiofs: Fix a comment about fuse_dev allocation virtiofs: Add an index to keep track of first request queue virtiofs: Decouple queue index and queue type virtiofs: Add a virtqueue for notifications virtiofs: Add a helper to end request and decrement inflight number virtiofs: Add new notification type FUSE_NOTIFY_LOCK virtiofs: Handle reordering of reply and notification event fs/fuse/virtio_fs.c | 438 ++++++++++++++++++++++++++++++--- include/uapi/linux/fuse.h | 11 +- include/uapi/linux/virtio_fs.h | 5 + 3 files changed, 412 insertions(+), 42 deletions(-) -- 2.31.1
