linux-kernel - Re: [PATCH 04/12] mm: Add readahead address space operation

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Message-ID: <4e28eb80-d602-47e6-51ec-63bb39e1a296@infradead.org>
Date:   Fri, 24 Jan 2020 19:57:40 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>, linux-fsdevel@...r.kernel.org
Cc:     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,
        linux-xfs@...r.kernel.org, cluster-devel@...hat.com,
        ocfs2-devel@....oracle.com
Subject: Re: [PATCH 04/12] mm: Add readahead address space operation

On 1/24/20 5:35 PM, Matthew Wilcox wrote:
> diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
> index 7d4d09dd5e6d..bb06fb7b120b 100644
> --- a/Documentation/filesystems/vfs.rst
> +++ b/Documentation/filesystems/vfs.rst
> @@ -706,6 +706,8 @@ cache in your filesystem.  The following members are defined:
>  		int (*readpage)(struct file *, struct page *);
>  		int (*writepages)(struct address_space *, struct writeback_control *);
>  		int (*set_page_dirty)(struct page *page);
> +		unsigned (*readahead)(struct file *filp, struct address_space *mapping,
> +				 pgoff_t start, unsigned nr_pages);
>  		int (*readpages)(struct file *filp, struct address_space *mapping,
>  				 struct list_head *pages, unsigned nr_pages);
>  		int (*write_begin)(struct file *, struct address_space *mapping,
> @@ -781,6 +783,15 @@ cache in your filesystem.  The following members are defined:
>  	If defined, it should set the PageDirty flag, and the
>  	PAGECACHE_TAG_DIRTY tag in the radix tree.
>  
> +``readahead``
> +	called by the VM to read pages associated with the address_space
> +	object.  The pages are consecutive in the page cache and are
> +        locked.  The implementation should decrement the page refcount after
> +        attempting I/O on each page.  Usually the page will be unlocked by
> +        the I/O completion handler.  If the function does not attempt I/O on
> +        some pages, return the number of pages which were not read so the
> +        common code can unlock the pages for you.
> +

Please use consistent indentation (tabs).

>  ``readpages``
>  	called by the VM to read pages associated with the address_space
>  	object.  This is essentially just a vector version of readpage.


cheers.
-- 
~Randy