Re: [PATCH v2] m: readahead: return the value which force_page_cache_readahead() returns

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 21 Aug 2013 10:41:20 +0800 Chen Gang <gang.chen@asianux.com> wrote:

> force_page_cache_readahead() may fail, so need let the related upper
> system calls know about it by its return value.
> 
> For system call fadvise64_64(), ignore return value because fadvise()
> shall return success even if filesystem can't retrieve a hint.
> 

Actually, force_page_cache_readahead() cannot fail - I see no code path
via which it returns a -ve errno.

Of course, that might change in the future and although readahead is
usually a best-effort-dont-care-if-it-fails thing, I suppose that in
the case of madvise() and sys_readahead() we should inform userspace,
as readhead is the primary reason for thier performing the syscall.


While we're there, please review...

From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm/readahead.c:do_readhead(): don't check for ->readpage

The callee force_page_cache_readahead() already does this and unlike
do_readahead(), force_page_cache_readahead() remembers to check for
->readpages() as well.



Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/readahead.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN mm/readahead.c~a mm/readahead.c
--- a/mm/readahead.c~a
+++ a/mm/readahead.c
@@ -569,7 +569,7 @@ static ssize_t
 do_readahead(struct address_space *mapping, struct file *filp,
 	     pgoff_t index, unsigned long nr)
 {
-	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+	if (!mapping || !mapping->a_ops)
 		return -EINVAL;
 
 	return force_page_cache_readahead(mapping, filp, index, nr);
_

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>