[Ocfs2-devel] [PATCH v2] ocfs2: check the metadate alloc before marking extent written
alex chen
alex.chen at huawei.com
Tue Dec 12 23:24:32 PST 2017
Hi Changwei,
On 2017/12/12 9:05, Changwei Ge wrote:
> Hi Alex,
>
> On 2017/12/5 11:31, alex chen wrote:
>> 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 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.
>>
>> Reported-by: John Lightsey <john at nixnuts.net>
>> Signed-off-by: Alex Chen <alex.chen at huawei.com>
>> Reviewed-by: Jun Piao <piaojun at huawei.com>
>> ---
>> fs/ocfs2/aops.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++----------
>> 1 file changed, 64 insertions(+), 13 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index d151632..7e1659d 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.
>> + */
>> + 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_NEEDED_SPLIT 2
>> 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 = 0;
>>
>> ocfs2_init_dealloc_ctxt(&dealloc);
>>
>> @@ -2328,10 +2356,10 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>
>> di = (struct ocfs2_dinode *)di_bh->b_data;
>>
>> +restart_all:
>> 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);
>> + ret = ocfs2_lock_allocators(inode, &et, 0, OCFS2_MAX_REC_NEEDED_SPLIT,
>> + NULL, &meta_ac);
>> if (ret) {
>> mlog_errno(ret);
>> goto unlock;
>> @@ -2343,7 +2371,7 @@ 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 +2380,17 @@ 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_NEEDED_SPLIT * 2);
>> + if (ret < 0) {
>> + mlog_errno(ret);
>> + break;
>> + } else if (ret == 1) {
>> + restart = 1;
>
> If there isn't enough extent records here, you break this loop and also
> commit transaction.
> After re-executing from _restart_all_, a new transaction is started.
> So you separate 'before _restart_all_' and 'after _restart_all_' into
> different transactions.
>
>
>> + break;
>> + }
>> +
>> ret = ocfs2_mark_extent_written(inode, &et, handle,
>> ue->ue_cpos, 1,
>> ue->ue_phys,
>> @@ -2361,24 +2399,37 @@ 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 && end > i_size_read(inode)) {
>
> Here you don't change inode size, however, obviously you already mark
> extents as *written*.
Here we should not change inode size, otherwise, the user may read some of the data
he wrote and the other part of data is zero, which breaks the consistency of WRITE.
Here it just mark extents to written and do not allocated data spaces.
>
>> ret = ocfs2_set_inode_size(handle, inode, di_bh, end);
>> if (ret < 0)
>> mlog_errno(ret);
>> }
>> +
>> commit:
>> ocfs2_commit_trans(osb, handle);
>
> You commit transaction here and host just crashes at this point.
> Then you will have a file with a smaller size than its real size.
> Moreover, those space could not be declaimed.
The problem you described above is exist. But it is a new problem and is not introduced by this patch.
It is introduced in commit c15471f79506(ocfs2: fix sparse file & data ordering issue in direct io).
Those space was allocated in ocfs2_dio_wr_get_block()->ocfs2_write_begin_nolock()->
ocfs2_write_cluster_by_desc() and it could not be declaimed when any errors happen in
ocfs2_dio_end_io_write().
This patch corrects the calculation method of the free number of the records.
At present, I have no idea to solve the new problem you described above, I think you can send the patch
to solve this problem if you have a good idea.
Thanks,
Alex
>
> Should we do more work on JBD2?
>
> Thanks,
> Changwei
>
>
>> +free_ac:
>> + if (meta_ac) {
>> + ocfs2_free_alloc_context(meta_ac);
>> + meta_ac = NULL;
>> + }
>> + if (restart) {
>> + restart = 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);
>>
>
>
> .
>
More information about the Ocfs2-devel
mailing list