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Date:   Wed, 24 Jun 2020 08:55:55 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH 1/5] f2fs: fix to wait page writeback before update
Message-ID: <20200624155555.GA215264@google.com>
References: <20200618063625.110273-1-yuchao0@huawei.com>
 <20200618235932.GA227771@google.com>
 <f5bbb14b-52a0-9697-a8fe-c3e39f78b0a5@huawei.com>
 <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>
 <da9df754-2e19-132c-9791-cac0361a1aad@huawei.com>
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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?

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