Re: [dm-devel] [PATCH 2/2] block: defer the use of inline biovecs for discard requests

[FUJITA Tomonori <fujita tomonori lab ntt co jp>]

On Sat, 26 Jun 2010 15:56:51 -0400
Mike Snitzer <snitzer redhat com> wrote:

> Don't alloc discard bio with a biovec in blkdev_issue_discard.  Doing so
> means bio_has_data() will not be true until the SCSI layer adds the
> payload to the discard request via blk_add_request_payload.
> 
> bio_{enable,disable}_inline_vecs are not expected to be widely used so
> they were exported using EXPORT_SYMBOL_GPL.
> 
> This patch avoids the need for the following VM accounting fix for
> discards: http://lkml.org/lkml/2010/6/23/361

Why do we need to avoid the above fix? Surely, the above fix is hacky
but much simpler than this patch.


> NOTE: Jens, you said you applied Tao Ma's fix but I cannot see it in
> your linux-2.6-block's for-next or for-2.6.36... as such I didn't revert
> it in this patch.
> 
> Signed-off-by: Mike Snitzer <snitzer redhat com>
> ---
>  block/blk-core.c    |    2 ++
>  block/blk-lib.c     |    2 +-
>  fs/bio.c            |   19 +++++++++++++++++--
>  include/linux/bio.h |    3 +++
>  4 files changed, 23 insertions(+), 3 deletions(-)