I talked to Christoph at the Plumbers Closing party, and he suggested that we get something simple in first which (a) assumes no on-disk format changes, (b) does everything in the VFS layer, by using a MS_CASE_FOLD, uses a case-insensitive dentry hash, and which degrades to a brute force search in the VFS by using readdir interfaces if the direct lookup does not succeed, and (c) at least initially assumes only ASCII. This could be extended by individual file systems who are willing to make on-disk format changes. It could be further extended later to support Unicode, and worse, different versions of Unicode. (The XFS patches you referenced support Unicode 7.0.0, and so they are already obsolete. Now we're up to Unicode 8.0.0. Fun.) The basic issue here is neither Christoph nor I are paid enough to worry about Unicode, and all of the hacks out there don't support Unicode anyway. If someone wants to pay Collabra $$$ to deal with the Unicode nightmare, life is simple if we let it degrade to brute force search, and they can have that work done under contract. :-) If we want to handle on-disk format changes, then the file system superblock would have to specify whether it's using ASCII, Unicode v7, Unicode v8, etc., and the kernel would have to provide helper routines to deal with all Unicode versions that we've ever supported before. I agree if we go down that path, we should have generic helper functions ala how we handled encryption. But the idea is get something basic in first, and then add other support later, incrementally. Christoph also suggested at the party that we should look at whether or not Android weird permissions system could be handled using an LSM. (It would have to be a stackable LSM, layered on top of SELinux.) That was definitely an intriguing idea, and much more likely to be sane than trying to use a wrapfs-based hack. The problem is I don't understand the weird Android permissions model well enough to know whether or not this is doable, but it's something I may try to take a look at if I can find enough round tuits. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
