On Tue, Apr 17, 2012 at 03:08:26PM -0700, Linus Torvalds wrote: > On Tue, Apr 17, 2012 at 2:14 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Tue, Apr 17, 2012 at 07:28:26PM +0100, Al Viro wrote:> > > Maybe instead I could continue using the i_mutex but handle rename some > > other way; e.g. in delegation code: > > > > if (!mutex_trylock(inode->i_mutex)) > > return -EAGAIN; > > if (atomic_read(inode->i_renames_in_progress)) > > return -EAGAIN; > > > > and add an > > > > atomic_inc(inode->i_renames_in_progress); > > atomic_dec(inode->i_renames_in_progress); > > > > pair around rename. > > Please don't make up your own locking. Plus it's broken anyway, since > a rename could come in directly after your atomic_read (and this is > *why* people shouldn't make up their own locks - they are invariably > broken). Doh, yes, sounds like a good rule. (I was misremembering some previous attempt at this--which admittedly may just have failed in some more complicated way.) --b. > > Or I could increment that counter for all the conflicting operations and > > rely on it instead of the i_mutex. I was trying to avoid adding > > something like that (an inc, a dec, another error path) to every > > operation. And hoping to avoid adding another field to struct inode. > > Oh well. > > We could just say that we can do a double inode lock, but then > standardize on the order. And the only sane order is comparing inode > pointers, not inode numbers like ext4 apparently does. > > With a standard order, I don't think it would be at all wrong to just > take the inode lock on rename. > > Linus -- 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
