From: Josef Bacik <jbacik@redhat.com> Date: Tue, 10 Feb 2009 13:49:15 -0500 Subject: [mm] revert KERNEL_DS buffered write optimisation Message-id: 1234291777-15344-3-git-send-email-jbacik@redhat.com O-Subject: [PATCH 02/24] [RHEL 5.4] mm: revert KERNEL_DS buffered write optimisation Bugzilla: 445433 RH-Acked-by: Steven Whitehouse <swhiteho@redhat.com> RH-Acked-by: Jeff Layton <jlayton@redhat.com> This upstream commit 41cb8ac025dbbf6782eae10d231e7e2336ad3724 and is in reference to bz 445433. This reverts a NFSD writev optimization. This is in preperation of taking the new aops patches. Signed-off-by: Josef Bacik <jbacik@redhat.com> diff --git a/mm/filemap.c b/mm/filemap.c index 63cdc94..d413c95 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2167,27 +2167,21 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, /* Limit the size of the copy to the caller's write size */ bytes = min(bytes, count); - /* We only need to worry about prefaulting when writes are from - * user-space. NFSd uses vfs_writev with several non-aligned - * segments in the vector, and limiting to one segment a time is - * a noticeable performance for re-write + /* + * Limit the size of the copy to that of the current segment, + * because fault_in_pages_readable() doesn't know how to walk + * segments. */ - if (!segment_eq(get_fs(), KERNEL_DS)) { - /* - * Limit the size of the copy to that of the current - * segment, because fault_in_pages_readable() doesn't - * know how to walk segments. - */ - bytes = min(bytes, cur_iov->iov_len - iov_base); + bytes = min(bytes, cur_iov->iov_len - iov_base); + + /* + * Bring in the user page that we will copy from _first_. + * Otherwise there's a nasty deadlock on copying from the + * same page as we're writing to, without it being marked + * up-to-date. + */ + fault_in_pages_readable(buf, bytes); - /* - * Bring in the user page that we will copy from - * _first_. Otherwise there's a nasty deadlock on - * copying from the same page as we're writing to, - * without it being marked up-to-date. - */ - fault_in_pages_readable(buf, bytes); - } page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec); if (!page) { status = -ENOMEM;