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Date:   Fri, 19 Jun 2020 15:47:55 -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: <20200619224755.GA60059@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>
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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?

> >>>>  			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);
> >>>> +
> >>>>  	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
> >>> .
> >>>
> > .
> >