On 30.07.2018 11:34, Misono Tomohiro wrote:
> On 2018/06/08 21:47, Nikolay Borisov wrote:
>> This commit pulls those portions of the kernel implementation of
>> delayed refs which are necessary to have them working in user-space.
>> I've done the following modifications:
>>
>> 1. Replaced all kmem_cache_alloc calls to kmalloc.
>>
>> 2. Removed all locking-related code, since we are single threaded in
>> userspace.
>>
>> 3. Removed code which deals with data refs - delayed refs in user space
>> are going to be used only for cowonly trees.
>>
>> Signed-off-by: Nikolay Borisov <[email protected]>
>> ---
>> Makefile | 3 +-
>> ctree.h | 3 +
>> delayed-ref.c | 608
>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> delayed-ref.h | 225 ++++++++++++++++++++++
>> extent-tree.c | 228 ++++++++++++++++++++++
>> kerncompat.h | 8 +
>> transaction.h | 4 +
>> 7 files changed, 1078 insertions(+), 1 deletion(-)
>> create mode 100644 delayed-ref.c
>> create mode 100644 delayed-ref.h
>>
>> diff --git a/Makefile b/Makefile
>> index 544410e6440c..9508ad4f11e6 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -116,7 +116,8 @@ objects = ctree.o disk-io.o kernel-lib/radix-tree.o
>> extent-tree.o print-tree.o \
>> qgroup.o free-space-cache.o kernel-lib/list_sort.o props.o \
>> kernel-shared/ulist.o qgroup-verify.o backref.o string-table.o
>> task-utils.o \
>> inode.o file.o find-root.o free-space-tree.o help.o send-dump.o \
>> - fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o
>> + fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o \
>> + delayed-ref.o
>> cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o
>> cmds-scrub.o \
>> cmds-inspect.o cmds-balance.o cmds-send.o cmds-receive.o \
>> cmds-quota.o cmds-qgroup.o cmds-replace.o check/main.o \
>> diff --git a/ctree.h b/ctree.h
>> index b30a946658ce..d1ea45571d1e 100644
>> --- a/ctree.h
>> +++ b/ctree.h
>> @@ -2812,4 +2812,7 @@ int btrfs_punch_hole(struct btrfs_trans_handle *trans,
>> int btrfs_read_file(struct btrfs_root *root, u64 ino, u64 start, int len,
>> char *dest);
>>
>> +
>> +/* extent-tree.c */
>> +int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, unsigned long
>> nr);
>> #endif
>> diff --git a/delayed-ref.c b/delayed-ref.c
>> new file mode 100644
>> index 000000000000..f3fa50239380
>> --- /dev/null
>> +++ b/delayed-ref.c
>> @@ -0,0 +1,608 @@
>
> <snip>
>
>> +
>> +static inline void drop_delayed_ref(struct btrfs_trans_handle *trans,
>> + struct btrfs_delayed_ref_root *delayed_refs,
>> + struct btrfs_delayed_ref_head *head,
>> + struct btrfs_delayed_ref_node *ref)
>> +{
>> + rb_erase(&ref->ref_node, &head->ref_tree);
>> + RB_CLEAR_NODE(&ref->ref_node);
>> + if (!list_empty(&ref->add_list))
>> + list_del(&ref->add_list);
>> + ref->in_tree = 0;
>> + btrfs_put_delayed_ref(ref);
>
> Compared with kernel code, it seems that we need
>
> delayed_refs->num_entries--;
>
>> + if (trans->delayed_ref_updates)
>> + trans->delayed_ref_updates--;
>> +}
>
>> +static noinline struct btrfs_delayed_ref_head *
>> +add_delayed_ref_head(struct btrfs_trans_handle *trans,
>> + struct btrfs_delayed_ref_head *head_ref,
>> + void *qrecord,
>> + int action, int *qrecord_inserted_ret,
>> + int *old_ref_mod, int *new_ref_mod)
>> +{
>> + struct btrfs_delayed_ref_head *existing;
>> + struct btrfs_delayed_ref_root *delayed_refs;
>> +
>> + delayed_refs = &trans->delayed_refs;
>> +
>> + existing = htree_insert(&delayed_refs->href_root, &head_ref->href_node);
>> + if (existing) {
>> + update_existing_head_ref(delayed_refs, existing, head_ref,
>> old_ref_mod);
>> + /*
>> + * we've updated the existing ref, free the newly
>> + * allocated ref
>> + */
>> + kfree(head_ref);
>> + head_ref = existing;
>> + } else {
>> + if (old_ref_mod)
>> + *old_ref_mod = 0;
>> + delayed_refs->num_heads++;
>> + delayed_refs->num_heads_ready++;
>
> And
> delayed_refs->num_entries++;
>
> to correctly count num_entries.
> (I noticed that num_entries went to negative value when I'm running gdb)
>
> However, num_entries is actually not used in progs at all (it is used for
> throttling in kernel), so maybe we can just drop the variable from progs?
I agree, will fix it on next respin. But for now I will wait for more
reviews.
>
>> + trans->delayed_ref_updates++;
>> + }
>> + if (new_ref_mod)
>> + *new_ref_mod = head_ref->total_ref_mod;
>> +
>> + return head_ref;
>> +}
>
> <snip>
>
>
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