mm, fadvise: don't return -EINVAL when filesystem cannot implement fadvise()
authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Tue, 31 Jul 2012 23:42:50 +0000 (16:42 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 1 Aug 2012 01:42:42 +0000 (18:42 -0700)
commit3d3727cdb07ff17ddc3c551ef8d03d37b60a0372
treec38036b00a6863a376cc592bc7d87a7560cb800d
parentc59e26104e3e0e952cd7d63e79cd71ee5a9ec25a
mm, fadvise: don't return -EINVAL when filesystem cannot implement fadvise()

Eric Wong reported his test suite failex when /tmp is tmpfs.

https://lkml.org/lkml/2012/2/24/479

Currentlt the input check of POSIX_FADV_WILLNEED has two problems.

- requires a_ops->readpage.  But in fact, force_page_cache_readahead()
  requires that the target filesystem has either ->readpage or ->readpages.

- returns -EINVAL when the filesystem doesn't have ->readpage.  But
  posix says that fadvise is merely a hint.  Thus fadvise() should return
  0 if filesystem has no means of implementing fadvise().  The userland
  application should not know nor care whcih type of filesystem backs the
  TMPDIR directory, as Eric pointed out.  There is nothing which userspace
  can do to solve this error.

So change the return value to 0 when filesytem doesn't support readahead.

[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Tested-by: Eric Wong <normalperson@yhbt.net>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/fadvise.c