Erez Zadok: > (1) Cache coherency: by far, the biggest concern had been around cache ::: > unionfs. The solution we have implemented is to compare the mtime/ctime of > upper/lower objects during revalidation (esp. of dentries); and if the lower > times are newer, we reconstruct the union object (drop the older objects, > and re-lookup them). This time-based cache-coherency works well and is ::: The resolution of mtime/ctime may be too low since some filesystems sets them in unit of a second, which means you cannot detect the changes made within a second. I think it is better to use inotify for every directory while it consumes a little more resources. Additionally, if you implement vm_operations instead of struggling along address_space_operations or VFS patches, in order to share the mmap-ed memory pages between lower inode and unionfs inode, then most of issues will be gone. You can see this approach and how it is working in http://aufs.sf.net (and get the source file from CVS). But I am afraid the approach sharing memory pages will not be avaiable for ecryptfs. Junjiro Okajima - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
