On Sun, 2012-07-08 at 02:00 +0900, OGAWA Hirofumi wrote: > "Steven J. Magnani" <st...@digidescorp.com> writes: > > >> You mean the unhashed inode is created by ->get_parent()? If so, the > >> root cause sounds like ->get_parent() itself. If not, I'm not > >> understanding the meaning of the temporary/unofficial inode here. > > > > Maybe "private" is a better word than "unofficial". Private inodes are > > created anywhere fat_new_inode (nee fat_build_unhashed_inode) is called > > directly, instead of through fat_build_inode. So yes, this is on the > > get_parent paths (via fat_lookup_dir), and also on the fh_to_dentry path > > when inode reconstruction is necessary. > > > > With private inodes, I don't see how anyone but the code that created > > them could find them to lock them. The reason they're private is that > > they're temporary aliases; at the time they're created, we don't have > > enough information to register them in a way that others could find > > them. A lookup, etc. operation will look for the inode of the "drivers" > > directory, not the ".." of the "usb" directory. We do need these private > > inodes in order to walk directory entries. I don't think they're a > > problem that needs solving; if we didn't use private inodes, we'd still > > need a way to walk directory entries in the context of these NFS > > operations, and there would still be potential races between that and > > other operations on the filesystem. > > How do you prevent to modify or free the those inode/blocks from other > path? Yeah, it is racy. And if races is not solved, that's simply wrong > and not solution. > > Although I'm not thinking deeply about NFS support on FAT. Just a idea, > the one of possible solutions would be register it to hash, and find it > on all path. So, all path will use same inode and lock. > > We need the key, possible key is - if it is only directory, FAT may be > able to use i_start as additional search key.
Interesting idea. I think this, and reformulating the FAT NFS file handle to include the parent's i_ino, will greatly simplify (and speed up) the code. I am having a hard time seeing how inclusion of i_pos in the file handle is useful. The only scenarios I can conceive where an i_ino lookup fails and an i_pos lookup succeeds are the object referenced by the file handle has: (A) been replaced by something else, or (2) had its inode evicted, but later re-instantiated Perhaps the design was intended to support case (2), but since the file handle of the re-instantiated inode will differ from the original (since i_ino and i_generation will have changed), NFS clients will cry ESTALE anyway. Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/