Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: Hi Andrew, > On Mon, 18 Apr 2022 17:37:10 -0400 Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx> wrote: > >> When provisioning containerized applications, multiple very small tmpfs > > "files"? Actually, filesystems. In cloud environments, we have several small tmpfs associated with containerized tasks. >> are used, for which one cannot always predict the proper file system >> size ahead of time. We want to be able to reliably monitor filesystems >> for ENOSPC errors, without depending on the application being executed >> reporting the ENOSPC after a failure. > > Well that sucks. We need a kernel-side workaround for applications > that fail to check and report storage errors? > > We could do this for every syscall in the kernel. What's special about > tmpfs in this regard? > > Please provide additional justification and usage examples for such an > extraordinary thing. For a cloud provider deploying containerized applications, they might not control the application, so patching userspace wouldn't be a solution. More importantly - and why this is shmem specific - they want to differentiate between a user getting ENOSPC due to insufficiently provisioned fs size, vs. due to running out of memory in a container, both of which return ENOSPC to the process. A system administrator can then use this feature to monitor a fleet of containerized applications in a uniform way, detect provisioning issues caused by different reasons and address the deployment. I originally submitted this as a new fanotify event, but given the specificity of shmem, Amir suggested the interface I'm implementing here. We've raised this discussion originally here: https://lore.kernel.org/linux-mm/CACGdZYLLCqzS4VLUHvzYG=rX3SEJaG7Vbs8_Wb_iUVSvXsqkxA@xxxxxxxxxxxxxx/ > Whatever that action is, I see no user-facing documentation which > guides the user info how to take advantage of this? I can follow up with a new version with documentation, if we agree this feature makes sense. Thanks, -- Gabriel Krisman Bertazi
