Re: [PATCH] mm: readahead: fix do_readahead for no readpage(s)

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Tue, Jan 28, 2014 at 11:14:19AM +0000, Mark Rutland wrote:
> Commit 63d0f0a3c7e1 (mm/readahead.c:do_readhead(): don't check for
> ->readpage) unintentionally made do_readahead return 0 for all valid
> files regardless of whether readahead was supported, rather than the
> expected -EINVAL. This gets forwarded on to userspace, and results in
> sys_readahead appearing to succeed in cases that don't make sense (e.g.
> when called on pipes or sockets). This issue is detected by the LTP
> readahead01 testcase.
> 
> As the exact return value of force_page_cache_readahead is currently
> never used, we can simplify it to return only 0 or -EINVAL (when
> readpage or readpages is missing). With that in place we can simply
> forward on the return value of force_page_cache_readahead in
> do_readahead.
> 
> This patch performs said change, restoring the expected semantics.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov