On Tue, May 19, 2009 at 06:15:52PM +0200, Miklos Szeredi wrote: > On Mon, 18 May 2009, Jan Blunck wrote: > > On union-mounted file systems the lookup function must also visit lower layers > > of the union-stack when doing a lookup. This patches add support for > > union-mounts to cached lookups and real lookups. > > > > We have 3 different styles of lookup functions now: > > - multiple pathname components, follow mounts, follow union, follow symlinks > > - single pathname component, doesn't follow mounts, follow union, doesn't > > follow symlinks > > - single pathname component doesn't follow mounts, doesn't follow unions, > > doesn't follow symlinks > > Ugh... I do wonder if this could be done in a less complicated way, > there does seem to be a fair amount of duplication between these > functions. Yeah, I agree. My best idea so far is not very good - have one skeleton function and pass in function pointers for the lookup_topmost() and build_union() functions. Do you have any ideas? > Worse, it looks like there are still i_mutex lock ordering issues > (__hash_lookup_topmost()/__hash_lookup_build_union()). What happens > if two separate unions of two filesystems are built where the order of > branches is reversed? We have a similar problem in union_copyup_dir(). Hm, thinking about this, only one of the file systems can actually change while we are doing work. That might help us get out of the lock ordering problems. Thoughts? -VAL -- 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
