linux-ext4 - Re: [PATCH v6 11/16] erofs: Convert compressed files from readpages to readahead

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Message-ID: <20200219023422.GA83440@architecture4>
Date:   Wed, 19 Feb 2020 10:34:22 +0800
From:   Gao Xiang <gaoxiang25@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linux-btrfs@...r.kernel.org>,
        <linux-erofs@...ts.ozlabs.org>, <linux-ext4@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <cluster-devel@...hat.com>, <ocfs2-devel@....oracle.com>,
        <linux-xfs@...r.kernel.org>
Subject: Re: [PATCH v6 11/16] erofs: Convert compressed files from readpages
 to readahead

On Mon, Feb 17, 2020 at 10:46:00AM -0800, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> 
> Use the new readahead operation in erofs.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>

It looks good to me, although some further optimization exists
but we could make a straight-forward transform first, and
I haven't tested the whole series for now...
Will test it later.

Acked-by: Gao Xiang <gaoxiang25@...wei.com>

Thanks,
Gao Xiang

> ---
>  fs/erofs/zdata.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 17f45fcb8c5c..7c02015d501d 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -1303,28 +1303,23 @@ static bool should_decompress_synchronously(struct erofs_sb_info *sbi,
>  	return nr <= sbi->max_sync_decompress_pages;
>  }
>  
> -static int z_erofs_readpages(struct file *filp, struct address_space *mapping,
> -			     struct list_head *pages, unsigned int nr_pages)
> +static void z_erofs_readahead(struct readahead_control *rac)
>  {
> -	struct inode *const inode = mapping->host;
> +	struct inode *const inode = rac->mapping->host;
>  	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
>  
> -	bool sync = should_decompress_synchronously(sbi, nr_pages);
> +	bool sync = should_decompress_synchronously(sbi, readahead_count(rac));
>  	struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
> -	gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
> -	struct page *head = NULL;
> +	struct page *page, *head = NULL;
>  	LIST_HEAD(pagepool);
>  
> -	trace_erofs_readpages(mapping->host, lru_to_page(pages)->index,
> -			      nr_pages, false);
> +	trace_erofs_readpages(inode, readahead_index(rac),
> +			readahead_count(rac), false);
>  
> -	f.headoffset = (erofs_off_t)lru_to_page(pages)->index << PAGE_SHIFT;
> -
> -	for (; nr_pages; --nr_pages) {
> -		struct page *page = lru_to_page(pages);
> +	f.headoffset = readahead_offset(rac);
>  
> +	readahead_for_each(rac, page) {
>  		prefetchw(&page->flags);
> -		list_del(&page->lru);
>  
>  		/*
>  		 * A pure asynchronous readahead is indicated if
> @@ -1333,11 +1328,6 @@ static int z_erofs_readpages(struct file *filp, struct address_space *mapping,
>  		 */
>  		sync &= !(PageReadahead(page) && !head);
>  
> -		if (add_to_page_cache_lru(page, mapping, page->index, gfp)) {
> -			list_add(&page->lru, &pagepool);
> -			continue;
> -		}
> -
>  		set_page_private(page, (unsigned long)head);
>  		head = page;
>  	}
> @@ -1366,11 +1356,10 @@ static int z_erofs_readpages(struct file *filp, struct address_space *mapping,
>  
>  	/* clean up the remaining free pages */
>  	put_pages_list(&pagepool);
> -	return 0;
>  }
>  
>  const struct address_space_operations z_erofs_aops = {
>  	.readpage = z_erofs_readpage,
> -	.readpages = z_erofs_readpages,
> +	.readahead = z_erofs_readahead,
>  };
>  
> -- 
> 2.25.0
> 
>