On Thu, Apr 14, 2016 at 08:10:49AM -0400, Brian Foster wrote: > On Wed, Apr 13, 2016 at 04:49:00PM +1000, Dave Chinner wrote: > > On Wed, Apr 13, 2016 at 03:31:28PM +1000, Dave Chinner wrote: > > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > > > The last thing we do before using call_rcu() on an xfs_inode to be > > > freed is mark it as invalid. This means there is a window between > > > when we know for certain that the inode is going to be freed and > > > when we do actually mark it as "freed". > > > > > > This is important in the context of RCU lookups - we can look up the > > > inode, find that it is valid, and then use it as such not realising > > > that it is in the final stages of being freed. > > > > > > As such, mark the inode as being invalid the moment we know it is > > > going to be reclaimed. This can be done while we still hold the > > > XFS_ILOCK_EXCL and the flush lock in xfs_inode_reclaim, meaning that > > > it occurs well before we remove it from the radix tree, and that > > > the i_flags_lock, the XFS_ILOCK and the inode flush lock all act as > > > synchronisation points for detecting that an inode is about to go > > > away. > > > > > > For defensive purposes, this allows us to add a further check to > > > xfs_iflush_cluster to ensure we skip inodes that are being freed > > > after we grab the XFS_ILOCK_SHARED and the flush lock - we know that > > > if the inode number if valid while we have these locks held we know > > > that it has not progressed through reclaim to the point where it is > > > clean and is about to be freed. > > > > > > [bfoster: fixed __xfs_inode_clear_reclaim() using ip->i_ino after it > > > had already been zeroed.] > > > > And, of course, in reordering this I dropped this fix because it was > > handled by the reworking of tagging code to use pag->pag_agno. > > > > So I've brought that small change forward to this patch (using > > pag->pag_agno instead of deriving it from the ip->i_ino in > > __xfs_inode_clear_reclaim()). > > > > I don't see any such change in this patch..? > __xfs_inode_clear_reclaim() still uses ip->i_ino. I meant that I realised that I'd screwed it up and so I'd changed my local copy after I sent this. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
