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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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 <20200619054922.GC227771@google.com>
 <3634ef79-5903-449d-0d52-3d5566481863@huawei.com>
 <20200619224755.GA60059@google.com>
 <3f49539a-7be1-be90-d13a-2f66a8483458@huawei.com>
 <20200621163834.GA36924@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <da9df754-2e19-132c-9791-cac0361a1aad@huawei.com>
Date:   Mon, 22 Jun 2020 08:51:14 +0800
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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;

> 
>>
>> 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
>>>>>>> .
>>>>>>>
>>>>> .
>>>>>
>>> .
>>>
> .
>