Hello Jan,
> btrfs_dec_ref() queued a delayed ref for owner of a tree block. The qgroup
> tracking is based on delayed refs. The owner of a tree block is set when a
> tree block is allocated, it is never updated.
>
> When you allocate a tree block and then remove the subvolume that did the
> allocation, the qgroup accounting for that removal is correct. However, the
> removal was accounted again for each subvolume deletion that also referenced
> the tree block, because accounting was erroneously based on the owner.
>
> Instead of queueing delayed refs for the non-existent owner, we now
> queue delayed refs for the root being removed. This fixes the qgroup
> accounting.
Thanks for tracking this, i apply your patch, and using the flowing patch,
found the problem still exist, the test script like the following:
#!/bin/sh
for i in $(seq 1000)
do
dd if=/dev/zero of=<mnt>/$i""aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa bs=10K count=1
done
btrfs sub snapshot <mnt> <mnt>/1
for i in $(seq 100)
do
btrfs sub snapshot <mnt>/$i <mnt>/$(($i+1))
done
for i in $(seq 101)
do
btrfs sub delete <mnt>/$i
done
Thanks,
Wang
>
> Signed-off-by: Jan Schmidt <list.btrfs@xxxxxxxxxxxxx>
> Tested-by: <dustymabe@xxxxxxxxx>
> ---
> fs/btrfs/extent-tree.c | 14 +++++++++-----
> 1 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index d58bef1..7846cae 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -3004,12 +3004,11 @@ out:
> static int __btrfs_mod_ref(struct btrfs_trans_handle *trans,
> struct btrfs_root *root,
> struct extent_buffer *buf,
> - int full_backref, int inc, int for_cow)
> + int full_backref, u64 ref_root, int inc, int for_cow)
> {
> u64 bytenr;
> u64 num_bytes;
> u64 parent;
> - u64 ref_root;
> u32 nritems;
> struct btrfs_key key;
> struct btrfs_file_extent_item *fi;
> @@ -3019,7 +3018,6 @@ static int __btrfs_mod_ref(struct btrfs_trans_handle *trans,
> int (*process_func)(struct btrfs_trans_handle *, struct btrfs_root *,
> u64, u64, u64, u64, u64, u64, int);
>
> - ref_root = btrfs_header_owner(buf);
> nritems = btrfs_header_nritems(buf);
> level = btrfs_header_level(buf);
>
> @@ -3075,13 +3073,19 @@ fail:
> int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
> struct extent_buffer *buf, int full_backref, int for_cow)
> {
> - return __btrfs_mod_ref(trans, root, buf, full_backref, 1, for_cow);
> + u64 ref_root;
> +
> + ref_root = btrfs_header_owner(buf);
> +
> + return __btrfs_mod_ref(trans, root, buf, full_backref, ref_root,
> + 1, for_cow);
> }
>
> int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
> struct extent_buffer *buf, int full_backref, int for_cow)
> {
> - return __btrfs_mod_ref(trans, root, buf, full_backref, 0, for_cow);
> + return __btrfs_mod_ref(trans, root, buf, full_backref, root->objectid,
> + 0, for_cow);
> }
>
> static int write_one_cache_group(struct btrfs_trans_handle *trans,
> --
> 1.7.2.2
>
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