On 2018/11/9 下午6:21, Filipe Manana wrote: > On Fri, Nov 9, 2018 at 12:27 AM Qu Wenruo <quwenruo.bt...@gmx.com> wrote: >> >> >> >> On 2018/11/8 下午10:48, Filipe Manana wrote: >>> On Thu, Nov 8, 2018 at 2:37 PM Filipe Manana <fdman...@kernel.org> wrote: >>>> >>>> On Thu, Nov 8, 2018 at 2:35 PM Qu Wenruo <quwenruo.bt...@gmx.com> wrote: >>>>> >>>>> >>>>> >>>>> On 2018/11/8 下午9:17, fdman...@kernel.org wrote: >>>>>> From: Filipe Manana <fdman...@suse.com> >>>>>> >>>>>> When creating a block group we don't need to set the log for full commit >>>>>> if the new block group is not used for data. Logged items can only point >>>>>> to logical addresses of data block groups (through file extent items) so >>>>>> there is no need to for the next fsync to fallback to a transaction >>>>>> commit >>>>>> if the new block group is for metadata. >>>>> >>>>> Is it possible for the log tree blocks to be allocated in that new block >>>>> group? >>>> >>>> Yes. >>> >>> Now I realize what might be your concern, and this would cause trouble. >>> Surprised this didn't trigger any problem and I had this (together >>> with other changes) running tests for some weeks already. >> >> Maybe it's related metadata chunk pre-allocation so it will be super >> hard to hit in normal case, or some extent allocation policy preventing >> us from allocating tree block of newly created bg. > > No, I don't think we have such kind of policy, would have noticed it > over the years if we did have one. > Metadata chunk allocation just happens much less frequently for > workloads the tests exercised.
Then smaller fs along with 4K nodesize would help, but I'm still not sure if we could hit such case. Thanks, Qu > >> >> Thanks, >> Qu >> >>> >>>> >>>>> >>>>> Thanks, >>>>> Qu >>>>> >>>>>> >>>>>> Signed-off-by: Filipe Manana <fdman...@suse.com> >>>>>> --- >>>>>> fs/btrfs/extent-tree.c | 3 ++- >>>>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c >>>>>> index 577878324799..588fbd1606fb 100644 >>>>>> --- a/fs/btrfs/extent-tree.c >>>>>> +++ b/fs/btrfs/extent-tree.c >>>>>> @@ -10112,7 +10112,8 @@ int btrfs_make_block_group(struct >>>>>> btrfs_trans_handle *trans, u64 bytes_used, >>>>>> struct btrfs_block_group_cache *cache; >>>>>> int ret; >>>>>> >>>>>> - btrfs_set_log_full_commit(fs_info, trans); >>>>>> + if (type & BTRFS_BLOCK_GROUP_DATA) >>>>>> + btrfs_set_log_full_commit(fs_info, trans); >>>>>> >>>>>> cache = btrfs_create_block_group_cache(fs_info, chunk_offset, >>>>>> size); >>>>>> if (!cache) >>>>>> >>>>> >>
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