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. 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:
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 "
--
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
