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Subject: Re: [PATCH 1/5] f2fs: fix to wait page writeback before update
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20200618063625.110273-1-yuchao0@huawei.com>
 <20200618235932.GA227771@google.com>
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 <3f49539a-7be1-be90-d13a-2f66a8483458@huawei.com>
 <20200621163834.GA36924@google.com>
 <da9df754-2e19-132c-9791-cac0361a1aad@huawei.com>
 <20200624155555.GA215264@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <27e196fe-276c-e88f-75a9-cd21c873ffd7@huawei.com>
Date:   Sun, 28 Jun 2020 09:26:05 +0800
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On 2020/6/24 23:55, Jaegeuk Kim wrote:
> On 06/22, Chao Yu wrote:
>> On 2020/6/22 0:38, Jaegeuk Kim wrote:
>>> On 06/20, Chao Yu wrote:
>>>> On 2020/6/20 6:47, Jaegeuk Kim wrote:
>>>>> On 06/19, Chao Yu wrote:
>>>>>> On 2020/6/19 13:49, Jaegeuk Kim wrote:
>>>>>>> On 06/19, Chao Yu wrote:
>>>>>>>> Hi Jaegeuk,
>>>>>>>>
>>>>>>>> On 2020/6/19 7:59, Jaegeuk Kim wrote:
>>>>>>>>> Hi Chao,
>>>>>>>>>
>>>>>>>>> On 06/18, Chao Yu wrote:
>>>>>>>>>> to make page content stable for special device like raid.
>>>>>>>>>
>>>>>>>>> Could you elaborate the problem a bit?
>>>>>>>>
>>>>>>>> Some devices like raid5 wants page content to be stable, because
>>>>>>>> it will calculate parity info based page content, if page is not
>>>>>>>> stable, parity info could be corrupted, result in data inconsistency
>>>>>>>> in stripe.
>>>>>>>
>>>>>>> I don't get the point, since those pages are brand new pages which were not
>>>>>>> modified before. If it's on writeback, we should not modify them regardless
>>>>>>> of whatever raid configuration. For example, f2fs_new_node_page() waits for
>>>>>>> writeback. Am I missing something?
>>>>>>
>>>>>> I think we should use f2fs_bug_on(, PageWriteback()) rather than
>>>>>> f2fs_wait_on_page_writeback() for brand new page which is allocated just now.
>>>>>> For other paths, we can keep rule that waiting for writeback before updating.
>>>>>>
>>>>>> How do you think?
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>>>>>>> ---
>>>>>>>>>>  fs/f2fs/dir.c          |  2 ++
>>>>>>>>>>  fs/f2fs/extent_cache.c | 18 +++++++++---------
>>>>>>>>>>  fs/f2fs/f2fs.h         |  2 +-
>>>>>>>>>>  fs/f2fs/file.c         |  1 +
>>>>>>>>>>  fs/f2fs/inline.c       |  2 ++
>>>>>>>>>>  fs/f2fs/inode.c        |  3 +--
>>>>>>>>>>  6 files changed, 16 insertions(+), 12 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
>>>>>>>>>> index d35976785e8c..91e86747a604 100644
>>>>>>>>>> --- a/fs/f2fs/dir.c
>>>>>>>>>> +++ b/fs/f2fs/dir.c
>>>>>>>>>> @@ -495,6 +495,8 @@ static int make_empty_dir(struct inode *inode,
>>>>>>>>>>  	if (IS_ERR(dentry_page))
>>>>>>>>>>  		return PTR_ERR(dentry_page);
>>>>>>>>>>  
>>>>>>>>>> +	f2fs_bug_on(F2FS_I_SB(inode), PageWriteback(dentry_page));
>>>>>>>>>> +
>>>>>>>>>>  	dentry_blk = page_address(dentry_page);
>>>>>>>>>>  
>>>>>>>>>>  	make_dentry_ptr_block(NULL, &d, dentry_blk);
>>>>>>>>>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>>>>>>>>>> index e60078460ad1..686c68b98610 100644
>>>>>>>>>> --- a/fs/f2fs/extent_cache.c
>>>>>>>>>> +++ b/fs/f2fs/extent_cache.c
>>>>>>>>>> @@ -325,9 +325,10 @@ static void __drop_largest_extent(struct extent_tree *et,
>>>>>>>>>>  }
>>>>>>>>>>  
>>>>>>>>>>  /* return true, if inode page is changed */
>>>>>>>>>> -static bool __f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext)
>>>>>>>>>> +static void __f2fs_init_extent_tree(struct inode *inode, struct page *ipage)
>>>>>>>>>>  {
>>>>>>>>>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>>>>>>> +	struct f2fs_extent *i_ext = ipage ? &F2FS_INODE(ipage)->i_ext : NULL;
>>>>>>>>>>  	struct extent_tree *et;
>>>>>>>>>>  	struct extent_node *en;
>>>>>>>>>>  	struct extent_info ei;
>>>>>>>>>> @@ -335,16 +336,18 @@ static bool __f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_e
>>>>>>>>>>  	if (!f2fs_may_extent_tree(inode)) {
>>>>>>>>>>  		/* drop largest extent */
>>>>>>>>>>  		if (i_ext && i_ext->len) {
>>>>>>>>>> +			f2fs_wait_on_page_writeback(ipage, NODE, true, true);
>>>>>>>>>>  			i_ext->len = 0;
>>>>>>>>>> -			return true;
>>>>>>>>>> +			set_page_dirty(ipage);
>>>>>>>>>> +			return;
>>>>>>>>>>  		}
>>>>>>>>>> -		return false;
>>>>>>>>>> +		return;
>>>>>>>>>>  	}
>>>>>>>>>>  
>>>>>>>>>>  	et = __grab_extent_tree(inode);
>>>>>>>>>>  
>>>>>>>>>>  	if (!i_ext || !i_ext->len)
>>>>>>>>>> -		return false;
>>>>>>>>>> +		return;
>>>>>>>>>>  
>>>>>>>>>>  	get_extent_info(&ei, i_ext);
>>>>>>>>>>  
>>>>>>>>>> @@ -360,17 +363,14 @@ static bool __f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_e
>>>>>>>>>>  	}
>>>>>>>>>>  out:
>>>>>>>>>>  	write_unlock(&et->lock);
>>>>>>>>>> -	return false;
>>>>>>>>>>  }
>>>>>>>>>>  
>>>>>>>>>> -bool f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext)
>>>>>>>>>> +void f2fs_init_extent_tree(struct inode *inode, struct page *ipage)
>>>>>>>>>>  {
>>>>>>>>>> -	bool ret =  __f2fs_init_extent_tree(inode, i_ext);
>>>>>>>>>> +	__f2fs_init_extent_tree(inode, ipage);
>>>>>>>>>>  
>>>>>>>>>>  	if (!F2FS_I(inode)->extent_tree)
>>>>>>>>>>  		set_inode_flag(inode, FI_NO_EXTENT);
>>>>>>>>>> -
>>>>>>>>>> -	return ret;
>>>>>>>>>>  }
>>>>>>>>>>  
>>>>>>>>>>  static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
>>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>>>> index b35a50f4953c..326c12fa0da5 100644
>>>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>>>> @@ -3795,7 +3795,7 @@ struct rb_entry *f2fs_lookup_rb_tree_ret(struct rb_root_cached *root,
>>>>>>>>>>  bool f2fs_check_rb_tree_consistence(struct f2fs_sb_info *sbi,
>>>>>>>>>>  						struct rb_root_cached *root);
>>>>>>>>>>  unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink);
>>>>>>>>>> -bool f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext);
>>>>>>>>>> +void f2fs_init_extent_tree(struct inode *inode, struct page *ipage);
>>>>>>>>>>  void f2fs_drop_extent_tree(struct inode *inode);
>>>>>>>>>>  unsigned int f2fs_destroy_extent_node(struct inode *inode);
>>>>>>>>>>  void f2fs_destroy_extent_tree(struct inode *inode);
>>>>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>>>>>>> index 3268f8dd59bb..1862073b96d2 100644
>>>>>>>>>> --- a/fs/f2fs/file.c
>>>>>>>>>> +++ b/fs/f2fs/file.c
>>>>>>>>>> @@ -1250,6 +1250,7 @@ static int __clone_blkaddrs(struct inode *src_inode, struct inode *dst_inode,
>>>>>>>>>>  				f2fs_put_page(psrc, 1);
>>>>>>>>>>  				return PTR_ERR(pdst);
>>>>>>>>>>  			}
>>>>>>>>>> +			f2fs_wait_on_page_writeback(pdst, DATA, true, true);
>>>>>
>>>>> Do you mean pdst can be under writeback?
>>>>
>>>> Use f2fs_bug_on(, dirty || writeback) here?
>>>>
>>>>>
>>>>>>>>>>  			f2fs_copy_page(psrc, pdst);
>>>>>>>>>>  			set_page_dirty(pdst);
>>>>>>>>>>  			f2fs_put_page(pdst, 1);
>>>>>>>>>> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
>>>>>>>>>> index dbade310dc79..4bcbc486c9e2 100644
>>>>>>>>>> --- a/fs/f2fs/inline.c
>>>>>>>>>> +++ b/fs/f2fs/inline.c
>>>>>>>>>> @@ -340,6 +340,8 @@ int f2fs_make_empty_inline_dir(struct inode *inode, struct inode *parent,
>>>>>>>>>>  	struct f2fs_dentry_ptr d;
>>>>>>>>>>  	void *inline_dentry;
>>>>>>>>>>  
>>>>>>>>>> +	f2fs_wait_on_page_writeback(ipage, NODE, true, true);
>>>>
>>>> f2fs_bug_on(, writeback)?
>>>
>>> So, which case do you suspect unstable page for raid?
>>
>> - gc_node_segment
>>  - f2fs_move_node_page
>>   - __write_node_page
>>    - set_page_writeback
>>
>> - do_read_inode
>>  - f2fs_init_extent_tree
>>   - __f2fs_init_extent_tree
>>     i_ext->len = 0;
> 
> Could you please add wait_on_writeback on this specific case only
> with this backtrace in the description?

Sure, :)

Thanks,

> 
> Thanks,
> 
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>>>>>> +
>>>>>>>>>>  	inline_dentry = inline_data_addr(inode, ipage);
>>>>>>>>>>  
>>>>>>>>>>  	make_dentry_ptr_inline(inode, &d, inline_dentry);
>>>>>>>>>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>>>>>>>>>> index 44582a4db513..7c156eb26dd7 100644
>>>>>>>>>> --- a/fs/f2fs/inode.c
>>>>>>>>>> +++ b/fs/f2fs/inode.c
>>>>>>>>>> @@ -367,8 +367,7 @@ static int do_read_inode(struct inode *inode)
>>>>>>>>>>  	fi->i_pino = le32_to_cpu(ri->i_pino);
>>>>>>>>>>  	fi->i_dir_level = ri->i_dir_level;
>>>>>>>>>>  
>>>>>>>>>> -	if (f2fs_init_extent_tree(inode, &ri->i_ext))
>>>>>>>>>> -		set_page_dirty(node_page);
>>>>>>>>>> +	f2fs_init_extent_tree(inode, node_page);
>>>>>>>>>>  
>>>>>>>>>>  	get_inline_info(inode, ri);
>>>>>>>>>>  
>>>>>>>>>> -- 
>>>>>>>>>> 2.18.0.rc1
>>>>>>>>> .
>>>>>>>>>
>>>>>>> .
>>>>>>>
>>>>> .
>>>>>
>>> .
>>>
> .
>