[PATCH] generic_file_buffered_write fixes

[PATCH] generic_file_buffered_write fixes

Anton Altaparmakov <aia21@cam.ac.uk> points out:

- It calls fault_in_pages_readable() which is completely bogus if @nr_segs >
  1.  It needs to be replaced by a to be written
  "fault_in_pages_readable_iovec()".

- It increments @buf even in the iovec case thus @buf can point to random
  memory really quickly (in the iovec case) and then it calls
  fault_in_pages_readable() on this random memory.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>