Hi, We have a case where our virtio-fs FUSE device (running on Bluefield DPU) needs to invalidate some of its internal file objects, so that it can free memory to be used for file objects for newly looked up files. We cannot rely on the host to invalidate entries itself since it typically has far more memory for its caches than is available on a real hardware device for its file object caching.
We would like to use the FUSE_NOTIFY_INVAL_ENTRY notification to ask the host to invalidate inodes, triggering FUSE FORGET commands that will enable the device to free its associated file objects for those inodes. We cannot find any documentation that explicitly says FUSE_NOTIFY_INVAL_ENTRY can be used for this purpose. But initial testing and code inspection indicates that this does trigger the FORGET commands that allow us to free some of the file objects in device memory. Can we safely depend on the FUSE_NOTIFY_INVAL_ENTRY notifications to trigger FORGET commands for the associated inodes? If not, can we consider adding a new FUSE_NOTIFY_DROP_ENTRY notification that would ask the kernel to release the inode and send a FORGET command when memory pressure or clean-up is needed by the device? Best regards, Jim Harris
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