Al Viro: > Different ->i_mutex; you are holding one on the parent directory already. Let me make sure. In your scenario, - processA writes something into the union, and the unioning fs operates the writable layer. After sb_start_write() succeeds, processA should not block by the reason of fsfreeze. - processC causes the copyup. The current aufs implementation holds parent->i_mutex on the writable layer during the copyup. The parent->i_mutex can make processA blocking. Now I am considering the copyup approach you suggested in another mail, and I am going to replace your "unlink the target, re-link later, no dir lock during copyup" by "make it hidden instead of unlinking, rename the correct name later, no dir lock during copyup" since I am not sure all FSs can operate "->link with the unlinked one". I guess most FS can handle it, but I don't want to make sure everything particulary remote fs, journals. To make a file "hidden", I guess I can use the aufs "doubley whiteouted" approach. As you might know, aufs prepends the ".wh." prefix to the filename as whiteout. With one more prefix, the name loses the role of whiteout. Aufs simply ignores such doubly whiteouted name. The demerit is that aufs has to limit the length of the name. J. R. 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
