On 06/13/2013 01:42 AM, Al Viro wrote: > On Thu, Jun 13, 2013 at 03:01:22AM +0100, Al Viro wrote: >> On Fri, Jun 07, 2013 at 05:14:52PM +0100, Al Viro wrote: >>> On Fri, Jun 07, 2013 at 11:09:05AM -0500, Dave Chiluk wrote: >>>> Can't you just use the patch from my original e-mail? Anyhow I attached >>>> it an already signed-off patch. >>>> >>>> Al Viro Can you integrate it now? >>> >>> Applied... FWIW, patch directly in mail body is more convenient to deal with. >> >> Actually, looking at that stuff... Why are we bothering with -EBUSY for >> removal of busy directories on ncpfs, anyway? It's not just rmdir(), it's >> overwriting rename() as well. IS_DEADDIR checks in fs/namei.c and fs/readdir.c >> mean that the only method of ncpfs directories that might get called after >> successful removal is ->setattr() and it would be trivial to add the check >> in ncp_notify_change() that would make it fail for dead directories without >> bothering the server at all... >> >> Related question: what happens if you open / unlink / fchmod on ncpfs? > > Speaking of crap used only by ncpfs: I think we can use ->d_iput() to get rid > of d_validate() for good. The only remaining user is ncpfs; what happens there > is that we use the page cache of directory to cache the references to dentries > made by readdir. We could do the following trick: > * have ->d_fsdata for these dentries a pointer into the cache page where > the reference back to dentry is stored > * ->freepage() for those pages consisting of > grab global spinlock > go through all dentries still pointed to by pointers in that > page, zeroing ->d_fsdata > drop the spinlock > * ->d_iput() for those dentries consisting of > grab the same spinlock > if ->d_fsdata is non-zero, store NULL at the address pointed > to by it > drop the spinlock > * ncp_dget_fpos() would > grab that spinlock > check if the reference to dentry in the position we are > interested in is non-NULL > grab ->d_lock > if DCACHE_DENTRY_KILLED is not set > bump ->d_count > drop ->d_lock > drop the spinlock > return dentry > // dentry is doomed > clear the reference > drop ->d_lock > drop the spinlock > return NULL > * ncp_fill_cache() would insert the sucker into cache and set > ->d_fsdata under the same spinlock. > > IOW, instead of wanking with untrusted pointers to dentries, we simply make > sure we clean the pointer when dentry is going away and clean the reference > from dentry to the location of that pointer when the page is going away. > > Objections? I can do a patch along those lines, but I've nothing to test it > on. Had that been cifs, I could at least use samba to test the fucker, but > I've no idea how to do that with ncpfs and I'm not too fond of checking how > much bitrot has mars_nwe suffered... > I'm afraid you are way beyond my current vfs experience level on this one. While you're getting rid of things you might consider dentry_unhash as well, as only hpfs_unlink, ncp_rmdir, and ncp_rename call that. If you get a patch together, I'll do my best to test it. Looks like only ncp_readdir calls that, so afaik, a few varying ls commands should be all that's needed for a test. Dave. p.s. are you sure you don't just want to just deprecate all of ncpfs? -- 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
