On Tue, Aug 12, 2014 at 02:36:17PM -0400, Chris Mason wrote: > > > On 08/12/2014 02:32 PM, Mark Fasheh wrote: > > On Tue, Aug 12, 2014 at 02:22:31PM -0400, Chris Mason wrote: > >> > >> > >> On 07/17/2014 03:39 PM, Mark Fasheh wrote: > >>> During its tree walk, btrfs_drop_snapshot() will skip any shared > >>> subtrees it encounters. This is incorrect when we have qgroups > >>> turned on as those subtrees need to have their contents > >>> accounted. In particular, the case we're concerned with is when > >>> removing our snapshot root leaves the subtree with only one root > >>> reference. > >>> > >>> In those cases we need to find the last remaining root and add > >>> each extent in the subtree to the corresponding qgroup exclusive > >>> counts. > >>> > >>> This patch implements the shared subtree walk and a new qgroup > >>> operation, BTRFS_QGROUP_OPER_SUB_SUBTREE. When an operation of > >>> this type is encountered during qgroup accounting, we search for > >>> any root references to that extent and in the case that we find > >>> only one reference left, we go ahead and do the math on it's > >>> exclusive counts. > >>> > >>> Signed-off-by: Mark Fasheh <mfas...@suse.de> > >>> Reviewed-by: Josef Bacik <jba...@fb.com> > >>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > >>> index 813537f..1aa4325 100644 > >>> --- a/fs/btrfs/extent-tree.c > >>> +++ b/fs/btrfs/extent-tree.c > >>> @@ -8078,6 +8331,14 @@ int btrfs_drop_snapshot(struct btrfs_root *root, > >>> } > >>> root_dropped = true; > >>> out_end_trans: > >>> + ret = btrfs_delayed_qgroup_accounting(trans, root->fs_info); > >> ^^^^^^^^^^^ > >> > >> CONFIG_DEBUG_PAGEALLOC noticed that root is already free at this point. > >> I switched it to tree_root instead ;) > > > > Oh nice catch, thanks for pointing it out. > > > > Time to go update my suse patches. > > Grin, pretty sure it doesn't count as a catch if CONFIG_DEBUG_PAGEALLOC > finds it.
Fair enough, on my end I get to add CONFIG_DEBUG_PAGEALLOC to my testing :) > But it did make it through the balance test we were crashing > in before. It's probably faster to hand edit the incremental in for the > suse patch, but here you go just in case: Yeah we haven't hit anything internally and like I said we've been running with it for a while. It's probably hard to hit as I can promise that code has been executed more than a couple times by now. The delete-items path is definitely broken so maybe you hit something from that? Btw, I should be sending a two-liner fix that can be extracted from the delete-items patch soon. --Mark > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 763632d..ef0845d 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -8314,7 +8314,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root, > } > root_dropped = true; > out_end_trans: > - ret = btrfs_delayed_qgroup_accounting(trans, root->fs_info); > + ret = btrfs_delayed_qgroup_accounting(trans, tree_root->fs_info); > if (ret) > printk_ratelimited(KERN_ERR "BTRFS: Failure %d " > "running qgroup updates " -- Mark Fasheh -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html