MFC r235781:

MFC r235781:

Fix enforcement of file size limit with O_APPEND on ZFS.

vn_rlimit_fsize takes uio->uio_offset and uio->uio_resid into account
when determining whether given write would exceed RLIMIT_FSIZE.

When APPEND flag is specified, ZFS updates uio->uio_offset to point to the
end of file.

But this happens after a call to vn_rlimit_fsize, so vn_rlimit_fsize check
can be rendered ineffective by thread that opens some file with O_APPEND
and lseeks below RLIMIT_FSIZE before calling write.

git-svn-id: svn://svn.freebsd.org/base/stable/9@236636 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f