On Tue, Sep 27, 2016 at 5:10 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Mon, Sep 12, 2016 at 09:29:02PM +0200, Miklos Szeredi wrote: >> The first patch is actually a bug fix, but I put it into this bunch for >> simplicity... >> >> The rest are really cleanups as well as minor bugfixes that are byproducts >> of the cleanups. >> >> This series builds on the fact that i_op.readlink is already set to >> generic_readlink() in 43/50 of the cases. And of those 7 only 4 are doing >> something special. So more than 90% of readlinks are/could actually just >> call back into get_link. >> >> The interesting cases are: >> >> - AFS, which has readlink but not get_link >> - proc, that allow jumping while following symlinks >> >> The first is handled by setting IOP_NOFOLLOW on the inode by the fs. >> >> The second one is handled by introducing is_following_link() which returns >> a bool depending on whether current->nameidata is NULL or not. If it >> returns false ->get_link() should behave as ->readlink() did. Otherwise it >> should behave as id did previously. >> >> Builds and boots. Can even read symlinks. > > I have no problem with "let's get rid of generic_readlink" - not that > it bought us much, but sure, if you want to have decision made based upon > the combination of flags, let's do it. Just make NULL ->readlink + non-NULL > ->get_link() mean generic_readlink(), and we are done. Indeed. Except it really should be the other way round: - .get_link always returning the symlink body - only proc setting .jump_link to do its thing - RIP .readlink But that's an extra branch in the symlink following. I was worried about that and hence gone for the unification of the two. > > Overloading ->get_link() for procfs-style ones is just plain wrong, > though. Your current->nameidata != NULL thing is bloody brittle - what > happens if some code triggers those readlinks when called by something > during pathname resolution? Sure, right now existing callers won't. > But it doesn't take much to grow such a place _and_ have the implications > go unnoticed for quite a while. Yeah. We can do your above suggestion, it's certainly less brittle. But I think it's rather confusing, having ->get_link normally do readlink, except for proc, where readlink is done by ->readlink. Thanks, Miklos -- 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
