Re: [PATCH 09/15] ubifs: Convert ubifs_write_end() to use a folio

[Zhihao Cheng <chengzhihao1@huawei.com>]

在 2024/1/21 7:08, Matthew Wilcox (Oracle) 写道:
> Convert the incoming page pointer to a folio and use it throughout,
> saving several calls to compound_head().  Also remove some PAGE_SIZE
> assumptions.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>   fs/ubifs/file.c | 41 +++++++++++++++++++++--------------------
>   1 file changed, 21 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> index ef262499f228..52027b4feebf 100644
> --- a/fs/ubifs/file.c
> +++ b/fs/ubifs/file.c
> @@ -532,6 +532,7 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping,
>   			   loff_t pos, unsigned len, unsigned copied,
>   			   struct page *page, void *fsdata)
>   {
> +	struct folio *folio = page_folio(page);
>   	struct inode *inode = mapping->host;
>   	struct ubifs_inode *ui = ubifs_inode(inode);
>   	struct ubifs_info *c = inode->i_sb->s_fs_info;
> @@ -539,47 +540,47 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping,
>   	int appending = !!(end_pos > inode->i_size);
>   
>   	dbg_gen("ino %lu, pos %llu, pg %lu, len %u, copied %d, i_size %lld",
> -		inode->i_ino, pos, page->index, len, copied, inode->i_size);
> +		inode->i_ino, pos, folio->index, len, copied, inode->i_size);
>   
> -	if (unlikely(copied < len && len == PAGE_SIZE)) {
> +	if (unlikely(copied < len && !folio_test_uptodate(folio))) {
>   		/*
> -		 * VFS copied less data to the page that it intended and
> +		 * VFS copied less data to the folio than it intended and
>   		 * declared in its '->write_begin()' call via the @len
> -		 * argument. If the page was not up-to-date, and @len was
> -		 * @PAGE_SIZE, the 'ubifs_write_begin()' function did
> +		 * argument. If the folio was not up-to-date,
> +		 * the 'ubifs_write_begin()' function did
>   		 * not load it from the media (for optimization reasons). This
> -		 * means that part of the page contains garbage. So read the
> -		 * page now.
> +		 * means that part of the folio contains garbage. So read the
> +		 * folio now.
>   		 */
>   		dbg_gen("copied %d instead of %d, read page and repeat",
>   			copied, len);
> -		cancel_budget(c, page, ui, appending);
> -		ClearPageChecked(page);
> +		cancel_budget(c, &folio->page, ui, appending);
> +		folio_clear_checked(folio);
>   
>   		/*
>   		 * Return 0 to force VFS to repeat the whole operation, or the
>   		 * error code if 'do_readpage()' fails.
>   		 */
> -		copied = do_readpage(page);
> +		copied = do_readpage(&folio->page);
>   		goto out;
>   	}
>   
> -	if (len == PAGE_SIZE)
> -		SetPageUptodate(page);
> +	if (len >= folio_size(folio))
> +		folio_mark_uptodate(folio);

So I think 'len == folio_size(folio)' is right? Since len is passed from 
'bytes' which is recalculated after write_begin:
  if (bytes > folio_size(folio) - offset)
      bytes = folio_size(folio) - offset;
The 'len' can't be greater than folio_size.

>   
> -	if (!PagePrivate(page)) {
> -		attach_page_private(page, (void *)1);
> +	if (!folio->private) {
> +		folio_attach_private(folio, (void *)1);
>   		atomic_long_inc(&c->dirty_pg_cnt);
> -		__set_page_dirty_nobuffers(page);
> +		filemap_dirty_folio(mapping, folio);
>   	}
>   
>   	if (appending) {
>   		i_size_write(inode, end_pos);
>   		ui->ui_size = end_pos;
>   		/*
> -		 * Note, we do not set @I_DIRTY_PAGES (which means that the
> -		 * inode has dirty pages), this has been done in
> -		 * '__set_page_dirty_nobuffers()'.
> +		 * We do not set @I_DIRTY_PAGES (which means that
> +		 * the inode has dirty pages), this was done in
> +		 * filemap_dirty_folio().
>   		 */
>   		__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
>   		ubifs_assert(c, mutex_is_locked(&ui->ui_mutex));
> @@ -587,8 +588,8 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping,
>   	}
>   
>   out:
> -	unlock_page(page);
> -	put_page(page);
> +	folio_unlock(folio);
> +	folio_put(folio);
>   	return copied;
>   }
>   
> 


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