Lennart Poettering
088696fe29
Before this patch we'd resolve all symlinks of bind mounts and other mount points to establish for a service in advance, and only then start mounting them. This is problematic, if symlink chains jump around between directories in a namespace tree, so that to resolve a specific symlink chain we need to establish another mount already. A typical case where this happens is if /etc/resolv.conf is a symlink to some file in /run: in that case we'd normally resolve and mount /etc/resolv.conf early on, but that's broken, as to do this properly we'd need to resolve /etc/resolv.conf first, then figure out that /run needs to be mounted before we can proceed, and thus reorder the order in which we apply mounts dynamically. With this change, whenever we are about to apply a mount, we'll do a single step of the symlink normalization process, patch the mount entry accordingly, and then sort the list of mounts to establish again, taking the new path into account. This means that we can correctly deal with the example above: we might start with wanting to mount /etc/resolv.conf early, but after resolving it to the path in /run/ we'd push it to the end of the list, ensuring that /run is mounted first. (Note that this also fixes another bug: we were following symlinks on the bind mount source relative to the root directory of the service, rather than of the host. That's wrong though as we explicitly document tha the source of bind mounts is always on the host.)
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