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mm: revert KERNEL_DS buffered write optimisation 

Revert the patch from Neil Brown to optimise NFSD writev handling.

Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-10-16 01:24:53 -07:00 committed by Linus Torvalds
parent 902aaed0d9
commit 41cb8ac025
1 changed files with 13 additions and 19 deletions
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22
mm/filemap.c
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@ -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
*/
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.
* 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);
/*
* 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.
* 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;