On Wed, 21 Aug 2013 10:41:20 +0800 Chen Gang <gang.chen@xxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx>
---
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);
_
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