On Fri, 1 June 2007 09:59:17 +0100, Anton Altaparmakov wrote: > > I agree that your patch is a good idea. I reviewed the latest > incarnation and it makes sense to me. And your comment concerning Thanks. > the flags is a very welcome addition. Probably ought to find its way > into Documentation/filesystems/Locking or vfs.txt or somewhere like > that also. Might make sense. Right now I would be more interested in getting the questions at the bottom answered. Possibly the right answer might be "here is a patch to fix it". > Note that once your patch is applied I think it would make sense to > follow up with a second patch to remove the I_LOCK flag completely. > The only remaining uses are either together with I_NEW in which case > I_LOCK can be removed altogether or can be substituted with I_NEW > when only I_LOCK is used. This is because no places remain where we > set I_LOCK by itself any more with your patch. The only place where > we set it is the place where a new inode gets created in memory and > in that place we also set I_NEW at the same time as I_LOCK. > wait_on_inode() can then be changed to wait on I_NEW instead of on > I_LOCKED. That way we have one less confusing flag to worry about > and things are much easier to understand. True. Waiting on I_NEW would be equivalent to waiting on I_LOCK. To some degree I still prefer the current method. I_NEW is a state, while I_LOCK is a lock or completion method. Having a confusing mix of state/lock/completion bits is bad enough. Having such a mix of uses for a single bit could be even worse. > >I still suspect that NTFS has hit the same deadlock and its current > >"fix" will cause data corruption instead. > > The NTFS "fix" will not cause data corruption at all. The usage in > NTFS is very different... I am afraid your patch does not address > the deadlock with NTFS or rather it only addresses the inode write > deadlock and does not address the get_new_inode() deadlock that > exists with ilookup5() and is avoided by ilookup5_nowait(). This > deadlock is inherent to what NTFS does so you don't need to worry > about it. (If you want I am happy to explain it but I would rather > not waste my time explaining if no-one except me cares about it...) Two seperate deadlocks exist, we agree on this. I_SYNC only solves one of the two. LogFS solved the second deadlock by implementing its own destroy_inode() and drop_inode() methods. Any inodes that would cause the get_new_inode() deadlock get cached and logfs implements its own iget() method to return a cached inode from any deadlock-prone codepath. It is not a pretty solution, but ilookup_nowait() would definitely cause data corruption for logfs, so that was not an option. Better ideas are very welcome. Jörn -- The strong give up and move away, while the weak give up and stay. -- unknown - 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
