vfs: Return -ENXIO for negative SEEK_HOLE / SEEK_DATA offsets

commit fc46820b27a2d9a46f7e90c9ceb4a64a1bc5fab8 upstream.

In generic_file_llseek_size, return -ENXIO for negative offsets as well
as offsets beyond EOF.  This affects filesystems which don't implement
SEEK_HOLE / SEEK_DATA internally, possibly because they don't support
holes.

Fixes xfstest generic/448.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: s/eof/i_size_read(inode)/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc fs/read_write.c
Simple merge