Hi Changwei,
Thanks for your reviews.
On 2017/11/24 15:03, Changwei Ge wrote:
> Hi Alex,
> I just reviewed your patch and a few questions were come up with.
>
> On 2017/11/24 13:49, alex chen wrote:
>> Hi John,
>>
>> I think a better method to solve this problem.
>>
>> On 2017/11/22 5:05, John Lightsey wrote:
>>> On Tue, 2017-11-21 at 05:58 +0000, Changwei Ge wrote:
>>>
>>>> Can your tell me how did you format your volume?
>>>> What's your _cluster size_ and _block size_?
>>>> Your can obtain such information via debugfs.ocfs2 <your volume> -R
>>>> 'stats' | grep 'Cluster Size'
>>>>
>>>> It's better for you provide a way to reproduce this issue so that we
>>>> can
>>>> perform some test.
>>>>
>>>
>>> The issue recurred in our cluster today, so at best my patch is just
>>> decreasing the frequency of the crashes.
>>
>> We need to check the free number of the records in each loop to mark extent
>> written,
>> because the last extent block may be changed through many times marking
>> extent written
>> and the num_free_extents also be changed. In the worst case, the
>> num_free_extents may
>> become less than at the beginning of the loop. So we should not estimate the
>> free
>> number of the records at the beginning of the loop to mark extent written.
>>
>
> From John's description, ::dw_zero_count was not calculated properly
> and your patch seems not to address this issue. Do you agree that it's
> possible that we get a wrong ::dw_zero_count?
Yes, the old dw_zero_count is not calculated properly, but we don't use it
because
we just need know the max needed number of splinting the one extent.
>
>> I'd appreciate it if you could test the following patch and feedback the
>> result.
>>
>> Signed-off-by: Alex Chen <alex.c...@huawei.com>
>> ---
>> fs/ocfs2/aops.c | 76
>> ++++++++++++++++++++++++++++++++++++++++++++++++---------
>> 1 file changed, 64 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index d151632..80725f2 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -2272,6 +2272,35 @@ static int ocfs2_dio_wr_get_block(struct inode
>> *inode, sector_t iblock,
>> return ret;
>> }
>>
>> +static int ocfs2_dio_should_restart(struct ocfs2_extent_tree *et,
>> + struct ocfs2_alloc_context *meta_ac, int max_rec_needed)
>> +{
>> + int status = 0, free_extents;
>> +
>> + free_extents = ocfs2_num_free_extents(et);
>> + if (free_extents < 0) {
>> + status = free_extents;
>> + mlog_errno(status);
>> + return status;
>> + }
>> +
>> + /*
>> + * there are two cases which could cause us to EAGAIN in the
>> + * we-need-more-metadata case:
>> + * 1) we haven't reserved *any*
>> + * 2) we are so fragmented, we've needed to add metadata too
>> + * many times.
>
> What does point 2 mean?
The point 2 mean we have reserved metadata, but the left bit in allocate context
is not enough for allocating a new extent block.
>
>> + */
>> + if (free_extents < max_rec_needed) {
>> + if (!meta_ac || (ocfs2_alloc_context_bits_left(meta_ac)
>> + < ocfs2_extend_meta_needed(et->et_root_el)))
>> + status = 1;
>> + }
>> +
>> + return status;
>> +}
>> +
>> +#define OCFS2_MAX_REC_NEED_SPLIT 2
>
> Um, I don't figure why the Maximum value is 2, I suppose this is less
> than previously estimated one.
the max needed number of splinting the one extent in the worst case - that
we're writing in
the middle of the extent.
>
>> static int ocfs2_dio_end_io_write(struct inode *inode,
>> struct ocfs2_dio_write_ctxt *dwc,
>> loff_t offset,
>> @@ -2281,14 +2310,13 @@ static int ocfs2_dio_end_io_write(struct inode
>> *inode,
>> struct ocfs2_extent_tree et;
>> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>> struct ocfs2_inode_info *oi = OCFS2_I(inode);
>> - struct ocfs2_unwritten_extent *ue = NULL;
>> + struct ocfs2_unwritten_extent *ue = NULL, *tmp_ue;
>> struct buffer_head *di_bh = NULL;
>> struct ocfs2_dinode *di;
>> - struct ocfs2_alloc_context *data_ac = NULL;
>> struct ocfs2_alloc_context *meta_ac = NULL;
>> handle_t *handle = NULL;
>> loff_t end = offset + bytes;
>> - int ret = 0, credits = 0, locked = 0;
>> + int ret = 0, credits = 0, locked = 0, restart_func = 0;
>
> I think _ restart_func_ is not named properly. Can we change it into
> realloc or something like that?
>
>>
>> ocfs2_init_dealloc_ctxt(&dealloc);
>>
>> @@ -2330,8 +2358,9 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>
>> ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
>>
>> - ret = ocfs2_lock_allocators(inode, &et, 0, dwc->dw_zero_count*2,
>> - &data_ac, &meta_ac);
>> +restart_all:
>> + ret = ocfs2_lock_allocators(inode, &et, 0, OCFS2_MAX_REC_NEED_SPLIT,
>> + NULL, &meta_ac);
>> if (ret) {
>> mlog_errno(ret);
>> goto unlock;
>> @@ -2343,7 +2372,7 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>> if (IS_ERR(handle)) {
>> ret = PTR_ERR(handle);
>> mlog_errno(ret);
>> - goto unlock;
>> + goto free_ac;
>> }
>> ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
>> OCFS2_JOURNAL_ACCESS_WRITE);
>> @@ -2352,7 +2381,17 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>> goto commit;
>> }
>>
>> - list_for_each_entry(ue, &dwc->dw_zero_list, ue_node) {
>> + list_for_each_entry_safe(ue, tmp_ue, &dwc->dw_zero_list, ue_node) {
>> + ret = ocfs2_dio_should_restart(&et, meta_ac,
>> + OCFS2_MAX_REC_NEED_SPLIT * 2);
>
> Why extent block's free record number would change during marking
> written, which compels code path has to re-alloc.
>
One way to set the last extent block is as following:
ocfs2_mark_extent_written
ocfs2_change_extent_flag
ocfs2_split_extent
ocfs2_try_to_merge_extent
ocfs2_rotate_tree_left
__ocfs2_rotate_tree_left
ocfs2_et_set_last_eb_blk
Thanks,
Alex
> Thanks,
> Changwei
>
>> + if (ret < 0) {
>> + mlog_errno(ret);
>> + break;
>> + } else if (ret == 1) {
>> + restart_func = 1;
>> + break;
>> + }
>> +
>> ret = ocfs2_mark_extent_written(inode, &et, handle,
>> ue->ue_cpos, 1,
>> ue->ue_phys,
>> @@ -2361,24 +2400,37 @@ static int ocfs2_dio_end_io_write(struct inode
>> *inode,
>> mlog_errno(ret);
>> break;
>> }
>> +
>> + dwc->dw_zero_count--;
>> + list_del_init(&ue->ue_node);
>> + spin_lock(&oi->ip_lock);
>> + list_del_init(&ue->ue_ip_node);
>> + spin_unlock(&oi->ip_lock);
>> + kfree(ue);
>> }
>>
>> - if (end > i_size_read(inode)) {
>> + if (!restart_func && end > i_size_read(inode)) {
>> ret = ocfs2_set_inode_size(handle, inode, di_bh, end);
>> if (ret < 0)
>> mlog_errno(ret);
>> }
>> +
>> commit:
>> ocfs2_commit_trans(osb, handle);
>> +free_ac:
>> + if (meta_ac) {
>> + ocfs2_free_alloc_context(meta_ac);
>> + meta_ac = NULL;
>> + }
>> + if (restart_func) {
>> + restart_func = 0;
>> + goto restart_all;
>> + }
>> unlock:
>> up_write(&oi->ip_alloc_sem);
>> ocfs2_inode_unlock(inode, 1);
>> brelse(di_bh);
>> out:
>> - if (data_ac)
>> - ocfs2_free_alloc_context(data_ac);
>> - if (meta_ac)
>> - ocfs2_free_alloc_context(meta_ac);
>> ocfs2_run_deallocs(osb, &dealloc);
>> if (locked)
>> inode_unlock(inode);
>>
>
>
> .
>
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