tree 9f4c83901b87b3c7d90d93c4b054c04ef4ef9700
parent a0132ac0f275434db32111b8cf7372d991899da3
author Mark Rutland <mark.rutland@arm.com> 1391033151 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1391041360 -0800

mm/readahead.c: fix do_readahead() for no readpage(s)

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>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>