Re: [f2fs-dev] [PATCH 2/2 v2] f2fs: avoid f2fs_bug_on if f2fs_get_meta_page_nofail got EIO

[Chao Yu]

On 2018/9/26 9:10, Chao Yu wrote:
> On 2018/9/26 8:18, Jaegeuk Kim wrote:
>> On 09/21, Chao Yu wrote:
>>> On 2018/9/21 5:46, Jaegeuk Kim wrote:
>>>> On 09/20, Chao Yu wrote:
>>>>> On 2018/9/19 1:56, Jaegeuk Kim wrote:
>>>>>> This patch avoids BUG_ON when f2fs_get_meta_page_nofail got EIO during
>>>>>> xfstests/generic/475.
>>>>>>
>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
>>>>>> ---
>>>>>> Change log from v1:
>>>>>>  - propagate errno
>>>>>>  - drop sum_pages
>>>>>>
>>>>>>  fs/f2fs/checkpoint.c | 10 +++++-----
>>>>>>  fs/f2fs/f2fs.h       |  2 +-
>>>>>>  fs/f2fs/gc.c         |  9 +++++++++
>>>>>>  fs/f2fs/node.c       | 32 ++++++++++++++++++++++++--------
>>>>>>  fs/f2fs/recovery.c   |  2 ++
>>>>>>  fs/f2fs/segment.c    |  3 +++
>>>>>>  6 files changed, 44 insertions(+), 14 deletions(-)
>>>>>>
>>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>>> index 01e0d8f5bbbe..1ddf332ce4b2 100644
>>>>>> --- a/fs/f2fs/checkpoint.c
>>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>>> @@ -119,11 +119,8 @@ struct page *f2fs_get_meta_page_nofail(struct f2fs_sb_info *sbi, pgoff_t index)
>>>>>>  		if (PTR_ERR(page) == -EIO &&
>>>>>>  				++count <= DEFAULT_RETRY_IO_COUNT)
>>>>>>  			goto retry;
>>>>>> -
>>>>>>  		f2fs_stop_checkpoint(sbi, false);
>>>>>> -		f2fs_bug_on(sbi, 1);
>>>>>>  	}
>>>>>> -
>>>>>>  	return page;
>>>>>>  }
>>>>>>  
>>>>>> @@ -1512,7 +1509,10 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>  	ckpt->checkpoint_ver = cpu_to_le64(++ckpt_ver);
>>>>>>  
>>>>>>  	/* write cached NAT/SIT entries to NAT/SIT area */
>>>>>> -	f2fs_flush_nat_entries(sbi, cpc);
>>>>>> +	err = f2fs_flush_nat_entries(sbi, cpc);
>>>>>> +	if (err)
>>>>>> +		goto stop;
>>>>>
>>>>> To make sure, if partial NAT pages become dirty, flush them back to device
>>>>> outside checkpoint() is not harmful, right?
>>>>
>>>> I think so.
>>>
>>> Oh, one more case, now we use NAT #0, if partial NAT pages were
>>> writebacked, then we start to use NAT #1, later, in another checkpoint(),
>>> we update those NAT pages again, we will write them to NAT #0, which is
>>> belong to last valid checkpoint(), it's may cause corrupted checkpoint in
>>> scenario of SPO. So it's harmfull, right?
>>
>> We already stopped checkpoint anymore, so there'd be no way to proceed another
>> checkpoint. Am I missing something?
> 
> You're right, we have called f2fs_stop_checkpoint(), so we are safe now. :)

Can we allow to writeback fs metadata (NAT/SIT/SSA) in prior to checkpoint
to mitigate IO stress of checkpoint?

Maybe below conditions can be consider to trigger writebacking:
a) dirty count of meta (NAT/SIT/SSA) exceeds threshold
b) exceed time threshold

Thanks,

> 
> Thanks,
> 
>>
>>>
>>> Thanks,
>>>
>>>>
>>>>>
>>>>>> +
>>>>>>  	f2fs_flush_sit_entries(sbi, cpc);
>>>>>>  
>>>>>>  	/* unlock all the fs_lock[] in do_checkpoint() */
>>>>>> @@ -1521,7 +1521,7 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>  		f2fs_release_discard_addrs(sbi);
>>>>>>  	else
>>>>>>  		f2fs_clear_prefree_segments(sbi, cpc);
>>>>>> -
>>>>>> +stop:
>>>>>>  	unblock_operations(sbi);
>>>>>>  	stat_inc_cp_count(sbi->stat_info);
>>>>>>  
>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>> index a0c868127a7c..29021dbc8f2a 100644
>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>> @@ -2895,7 +2895,7 @@ int f2fs_recover_xattr_data(struct inode *inode, struct page *page);
>>>>>>  int f2fs_recover_inode_page(struct f2fs_sb_info *sbi, struct page *page);
>>>>>>  int f2fs_restore_node_summary(struct f2fs_sb_info *sbi,
>>>>>>  			unsigned int segno, struct f2fs_summary_block *sum);
>>>>>> -void f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc);
>>>>>> +int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc);
>>>>>>  int f2fs_build_node_manager(struct f2fs_sb_info *sbi);
>>>>>>  void f2fs_destroy_node_manager(struct f2fs_sb_info *sbi);
>>>>>>  int __init f2fs_create_node_manager_caches(void);
>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>>> index 4bcc8a59fdef..c7d14282dbf4 100644
>>>>>> --- a/fs/f2fs/gc.c
>>>>>> +++ b/fs/f2fs/gc.c
>>>>>> @@ -1070,6 +1070,15 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>  	/* reference all summary page */
>>>>>>  	while (segno < end_segno) {
>>>>>>  		sum_page = f2fs_get_sum_page(sbi, segno++);
>>>>>> +		if (IS_ERR(sum_page)) {
>>>>>> +			end_segno = segno - 1;
>>>>>> +			for (segno = start_segno; segno < end_segno; segno++) {
>>>>>> +				sum_page = find_get_page(META_MAPPING(sbi),
>>>>>> +						GET_SUM_BLOCK(sbi, segno));
>>>>>> +				f2fs_put_page(sum_page, 0);
>>>>>
>>>>> find_get_page() will add one more reference on page, so we need to call
>>>>> f2fs_put_page(sum_page, 0) twice.
>>>>
>>>> Done.
>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>>> +			}
>>>>>> +			return PTR_ERR(sum_page);
>>>>>> +		}
>>>>>>  		unlock_page(sum_page);
>>>>>>  	}
>>>>>>  
>>>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>>>> index fa2381c0bc47..79b6fee354f7 100644
>>>>>> --- a/fs/f2fs/node.c
>>>>>> +++ b/fs/f2fs/node.c
>>>>>> @@ -126,6 +126,8 @@ static struct page *get_next_nat_page(struct f2fs_sb_info *sbi, nid_t nid)
>>>>>>  
>>>>>>  	/* get current nat block page with lock */
>>>>>>  	src_page = get_current_nat_page(sbi, nid);
>>>>>> +	if (IS_ERR(src_page))
>>>>>> +		return src_page;
>>>>>>  	dst_page = f2fs_grab_meta_page(sbi, dst_off);
>>>>>>  	f2fs_bug_on(sbi, PageDirty(src_page));
>>>>>>  
>>>>>> @@ -2265,15 +2267,19 @@ static int __f2fs_build_free_nids(struct f2fs_sb_info *sbi,
>>>>>>  						nm_i->nat_block_bitmap)) {
>>>>>>  			struct page *page = get_current_nat_page(sbi, nid);
>>>>>>  
>>>>>> -			ret = scan_nat_page(sbi, page, nid);
>>>>>> -			f2fs_put_page(page, 1);
>>>>>> +			if (IS_ERR(page)) {
>>>>>> +				ret = PTR_ERR(page);
>>>>>> +			} else {
>>>>>> +				ret = scan_nat_page(sbi, page, nid);
>>>>>> +				f2fs_put_page(page, 1);
>>>>>> +			}
>>>>>>  
>>>>>>  			if (ret) {
>>>>>>  				up_read(&nm_i->nat_tree_lock);
>>>>>>  				f2fs_bug_on(sbi, !mount);
>>>>>>  				f2fs_msg(sbi->sb, KERN_ERR,
>>>>>>  					"NAT is corrupt, run fsck to fix it");
>>>>>> -				return -EINVAL;
>>>>>> +				return ret;
>>>>>>  			}
>>>>>>  		}
>>>>>>  
>>>>>> @@ -2700,7 +2706,7 @@ static void __update_nat_bits(struct f2fs_sb_info *sbi, nid_t start_nid,
>>>>>>  		__clear_bit_le(nat_index, nm_i->full_nat_bits);
>>>>>>  }
>>>>>>  
>>>>>> -static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>> +static int __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>  		struct nat_entry_set *set, struct cp_control *cpc)
>>>>>>  {
>>>>>>  	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
>>>>>> @@ -2724,6 +2730,9 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>  		down_write(&curseg->journal_rwsem);
>>>>>>  	} else {
>>>>>>  		page = get_next_nat_page(sbi, start_nid);
>>>>>> +		if (IS_ERR(page))
>>>>>> +			return PTR_ERR(page);
>>>>>> +
>>>>>>  		nat_blk = page_address(page);
>>>>>>  		f2fs_bug_on(sbi, !nat_blk);
>>>>>>  	}
>>>>>> @@ -2769,12 +2778,13 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>  		radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
>>>>>>  		kmem_cache_free(nat_entry_set_slab, set);
>>>>>>  	}
>>>>>> +	return 0;
>>>>>>  }
>>>>>>  
>>>>>>  /*
>>>>>>   * This function is called during the checkpointing process.
>>>>>>   */
>>>>>> -void f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>> +int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>  {
>>>>>>  	struct f2fs_nm_info *nm_i = NM_I(sbi);
>>>>>>  	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
>>>>>> @@ -2784,6 +2794,7 @@ void f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>  	unsigned int found;
>>>>>>  	nid_t set_idx = 0;
>>>>>>  	LIST_HEAD(sets);
>>>>>> +	int err = 0;
>>>>>>  
>>>>>>  	/* during unmount, let's flush nat_bits before checking dirty_nat_cnt */
>>>>>>  	if (enabled_nat_bits(sbi, cpc)) {
>>>>>> @@ -2793,7 +2804,7 @@ void f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>  	}
>>>>>>  
>>>>>>  	if (!nm_i->dirty_nat_cnt)
>>>>>> -		return;
>>>>>> +		return 0;
>>>>>>  
>>>>>>  	down_write(&nm_i->nat_tree_lock);
>>>>>>  
>>>>>> @@ -2816,11 +2827,16 @@ void f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>  	}
>>>>>>  
>>>>>>  	/* flush dirty nats in nat entry set */
>>>>>> -	list_for_each_entry_safe(set, tmp, &sets, set_list)
>>>>>> -		__flush_nat_entry_set(sbi, set, cpc);
>>>>>> +	list_for_each_entry_safe(set, tmp, &sets, set_list) {
>>>>>> +		err = __flush_nat_entry_set(sbi, set, cpc);
>>>>>> +		if (err)
>>>>>> +			break;
>>>>>> +	}
>>>>>>  
>>>>>>  	up_write(&nm_i->nat_tree_lock);
>>>>>>  	/* Allow dirty nats by node block allocation in write_begin */
>>>>>> +
>>>>>> +	return err;
>>>>>>  }
>>>>>>  
>>>>>>  static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
>>>>>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
>>>>>> index 56d34193a74b..ba678efe7cad 100644
>>>>>> --- a/fs/f2fs/recovery.c
>>>>>> +++ b/fs/f2fs/recovery.c
>>>>>> @@ -355,6 +355,8 @@ static int check_index_in_prev_nodes(struct f2fs_sb_info *sbi,
>>>>>>  	}
>>>>>>  
>>>>>>  	sum_page = f2fs_get_sum_page(sbi, segno);
>>>>>> +	if (IS_ERR(sum_page))
>>>>>> +		return PTR_ERR(sum_page);
>>>>>>  	sum_node = (struct f2fs_summary_block *)page_address(sum_page);
>>>>>>  	sum = sum_node->entries[blkoff];
>>>>>>  	f2fs_put_page(sum_page, 1);
>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>>> index aa96a371aaf8..ab7386a7e9d3 100644
>>>>>> --- a/fs/f2fs/segment.c
>>>>>> +++ b/fs/f2fs/segment.c
>>>>>> @@ -2487,6 +2487,7 @@ static void change_curseg(struct f2fs_sb_info *sbi, int type)
>>>>>>  	__next_free_blkoff(sbi, curseg, 0);
>>>>>>  
>>>>>>  	sum_page = f2fs_get_sum_page(sbi, new_segno);
>>>>>> +	f2fs_bug_on(sbi, IS_ERR(sum_page));
>>>>>>  	sum_node = (struct f2fs_summary_block *)page_address(sum_page);
>>>>>>  	memcpy(curseg->sum_blk, sum_node, SUM_ENTRY_SIZE);
>>>>>>  	f2fs_put_page(sum_page, 1);
>>>>>> @@ -3971,6 +3972,8 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>>>>>  
>>>>>>  			se = &sit_i->sentries[start];
>>>>>>  			page = get_current_sit_page(sbi, start);
>>>>>> +			if (IS_ERR(page))
>>>>>> +				return PTR_ERR(page);
>>>>>>  			sit_blk = (struct f2fs_sit_block *)page_address(page);
>>>>>>  			sit = sit_blk->entries[SIT_ENTRY_OFFSET(sit_i, start)];
>>>>>>  			f2fs_put_page(page, 1);
>>>>>>
>>>>
>>>> .
>>>>
>>
>> .
>>
> 
> 
> 
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