On Fri, 2010-11-05 at 15:08 -0400, J. Bruce Fields wrote: > On Fri, Nov 05, 2010 at 01:38:05PM -0400, Mimi Zohar wrote: > > On Fri, 2010-11-05 at 12:28 -0400, J. Bruce Fields wrote: > > > On Fri, Nov 05, 2010 at 07:08:06AM -0400, Mimi Zohar wrote: > > > > > > Right, like the ima_file_check(), which is after the __dentry_open(). > > > > Al, is it possible to move the break_lease() in may_open() to later? > > > > > > That would still leave a race like: > > > > > > check count > > > bump count > > > break lease > > > set lease > > > > > > But we could extend the i_lock to prevent the lease being bumped between > > > the two steps on the right-hand side. > > > > The latest i_readcount patchset, i_readcount is atomic and doesn't > > require i_lock, at least for IMA. Have to think about this more .... > > > > > At that point I think we'd be done? We're assured the count is still > > > zero while the lease is added to the inode, so anyone in the process of > > > doing an open has yet to reach the break_lease, which will see the newly > > > added lease. > > > > > > That leaves the problem that leases really should be broken on anything > > > that changes the attributes or the dentries pointing to the inode: > > > setattr, link, unlink, rename, at least. > > > > For this reason, IMA is now taking i_mutex, preventing file metadata > > from changing. > > Lease code could do that as well. (Probably just with a trylock, > failing the setlease if we can't get the lock.) > > That misses rename, though, which doesn't take the i_mutex on the > renamed file. Which makes sense. fs/namei.c: vfs_rename_other() seems to be taking the i_mutex. Am I looking in the wrong place? > But a lease is used to give file server clients the right to do an open > locally, and we want them to be able to guarantee to applications that > the path (well, the last component, at least) still refers to the same > file at open time. Mimi -- 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
