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

[Chao Yu <yuchao0@huawei.com>]

On 2018/9/27 3:49, Jaegeuk Kim wrote:
> On 09/26, Chao Yu wrote:
>> 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@kernel.org>
>>>>>>>> ---
>>>>>>>> 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?
> 
> What's the point related to this patch?

It's not related to this patch.

> Anyway, do you mean f2fs_write_meta_pages is not enough?

Yup, f2fs_write_meta_pages can only flush summary pages, I guess we can
allow to flush dirty nat/sit entries to NAT/SIT blocks in some conditions,
and then flush those block in background.

Thanks,

> 
>>
>> 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);
>>>>>>>>
>>>>>>
>>>>>> .
>>>>>>
>>>>
>>>> .
>>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Linux-f2fs-devel mailing list
>>> Linux-f2fs-devel@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>
>>> .
>>>
> 
> .
>