On Tue, Jun 12, 2018 at 03:17:27PM -0700, Ilya Pronin wrote: > So the only way to remove a symlink from a project is to remove it? Yes. > Here's my use case. In Apache Mesos we use XFS project quotas for disk > space isolation. Every container sandbox is allocated its own project > ID. When the container terminates its project ID is unset from the > sandbox and files inside it, and can be used for other containers. > Sandboxes of terminated containers stay on the host for some time for > debugging, etc. With such approach the inability to remove projid from > symlinks presents a small problem: when a project ID is reused for a > new container, any lingering symlinks that still have that project ID > will contribute to disk usage of the new container. Typically not > much, but still that's inaccurate. I guess we'll need to change when > we "deallocate" projids. There isn't really much we can do in XFS about it. Traditionally in all Unix variants you can never get a file descriptor for a symlink, and all normal file operations always follow symlinks. So you need special new syscalls to handle the symlink. Now Linux added the O_PATH mount option a while ago which actually allows you to get a file descriptor on symlinks, but just very limited ones that do not actually support calls into the underlying file system. So to support your use case we'd either need a new lioctl system call, or some way to support limited ioctls on O_PATH fds. Either would be a VFS change and would turn into a huge discussion. Once that is done however wiring up the XFS bits would be trivial. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
