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

Randy Dunlap
2020-01-25T03:57:48Z

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