From 41cb8ac025dbbf6782eae10d231e7e2336ad3724 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 16 Oct 2007 01:24:53 -0700 Subject: mm: revert KERNEL_DS buffered write optimisation Revert the patch from Neil Brown to optimise NFSD writev handling. Cc: Neil Brown Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 32 +++++++++++++------------------- 1 file changed, 13 insertions(+), 19 deletions(-) (limited to 'mm/filemap.c') diff --git a/mm/filemap.c b/mm/filemap.c index 7989c44cb293..c504db18ac26 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1874,27 +1874,21 @@ 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; -- cgit v1.2.3-58-ga151