On 2018/08/08 15:04, Qu Wenruo wrote:
> When quota is enabled and we do a snapshot, we just update the 'excl'
> number of both snapshot src and dst to src's 'rfer' - nodesize.
>
> It's a quick hack to avoid quota rescan every time we create a snapshot
> and it works if src doesn't belong to other qgroups.
>
> But if we have higher level qgroups, such behavior only works for level
> 0 qgroups, and higher level qgroups don't get update, thus making qgroup
> number inconsistent.
>
> The problem of updating higher level qgroup numbers is, it's way to
> complex.
>
> Under the following case, it's pretty simple: (src is 257, dst is 258)
> 0/257 - 1/0, 0/258.
>
> In this case, we only need to modify 1/0 to reduce its 'excl'
>
> But under the following case, it will go out of control:
>
> 0/257 - 1/0, 0/258 - 1/1 (using -i option), 1/0 - 2/0, 1/1 - 2/0.
>
> So to make it simple, if snapshot src has higher level qgroups, just
> mark qgroup inconsistent and let later rescan to do its job.
>
> Reported-by: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> fs/btrfs/qgroup.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index ec4351fd7537..2b3d2dd1b735 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -2298,6 +2298,22 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
> if (!srcgroup)
> goto unlock;
>
> + /*
> + * If snapshot source is belonging to high level qgroups, it
> + * will be a more complex to hack the numbers.
> + * E.g. source is 257, snapshot is 258:
> + * 0/257 - 1/0, creating snapshot 258 will need to update 1/0
> + * It's too complex when higher level qgroup is involved.
> + * Mark qgroup inconsistent for later rescan
> + */
> + if (!list_empty(&srcgroup->groups)) {
> + btrfs_info_rl(fs_info,
> +"src qgroup 0/%llu belongs to higher level qgroup, creating snapshot for it need qgroup rescan",
> + srcid);
> + fs_info->qgroup_flags |=
> + BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
> + goto unlock;
> + }
> /*
> * We call inherit after we clone the root in order to make sure
> * our counts don't go crazy, so at this point the only
>
Thanks for the quick fix.
Tested-by/Reviewed-by: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>
However there is still another problem about removing relation:
(4.18-rc7 with above patch)
$ mkfs.btrfs -fq $DEV
$ mount $DEV /mnt
$ btrfs quota enable /mnt
$ btrfs qgroup create 1/0 /mnt
$ btrfs sub create /mnt/sub
$ btrfs qgroup assign 0/257 1/0 /mnt
$ dd if=/dev/urandom of=/mnt/sub/file bs=1k count=1000
$ btrfs sub snap /mnt/sub /mnt/snap
$ dmesg | tail -n 1
BTRFS info (device sdb7): src qgroup 0/257 belongs to higher level qgroup,
creating snapshot for it need qgroup rescan
$ btrfs quota rescan -w /mnt
$ btrfs qgroup show -pcre /mnt
qgroupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1016.00KiB 16.00KiB none none 1/0 ---
0/258 1016.00KiB 16.00KiB none none --- ---
1/0 1016.00KiB 16.00KiB none none --- 0/257
so far so good, but:
$ btrfs qgroup remove 0/257 1/0 /mnt
WARNING: quotas may be inconsistent, rescan needed
$ btrfs quota rescan -w /mnt
$ btrfs qgroup show -pcre /mnt
qgoupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1016.00KiB 16.00KiB none none --- ---
0/258 1016.00KiB 16.00KiB none none --- ---
1/0 1016.00KiB 16.00KiB none none --- ---
^^^^^^^^^^ ^^^^^^^^ not cleared
It seems some fix is needed for rescan too.
Thanks,
Misono
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
