On Thu, Jul 14, 2016 at 10:01:04AM +1000, Dave Chinner wrote:
> On Wed, Jul 13, 2016 at 12:16:33PM -0400, Brian Foster wrote:
> > xfs_buf_read_uncached() allocates an uncached buffer and performs a read
> > in one go. As part of the upcoming buftarg I/O accounting mechanism,
> > some sites may need to set flags on a buffer before I/O submission.
> >
> > Create a new helper to support the ability to set flags on a buffer
> > before it is submitted for I/O. This use case is the exception, so
> > create a wrapper for the original xfs_buf_read_uncached().
> >
> > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> > ---
> > fs/xfs/xfs_buf.c | 20 +++++++++++++++++---
> > fs/xfs/xfs_buf.h | 4 ++++
> > 2 files changed, 21 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> > index 4665ff6..f007713 100644
> > --- a/fs/xfs/xfs_buf.c
> > +++ b/fs/xfs/xfs_buf.c
> > @@ -693,13 +693,14 @@ xfs_buf_readahead_map(
> > * buffer containing the disk contents or nothing.
> > */
> > int
> > -xfs_buf_read_uncached(
> > +xfs_buf_read_uncached_flags(
> > struct xfs_buftarg *target,
> > xfs_daddr_t daddr,
> > size_t numblks,
> > int flags,
> > struct xfs_buf **bpp,
> > - const struct xfs_buf_ops *ops)
> > + const struct xfs_buf_ops *ops,
> > + int bflags)
> > {
>
> We already have a flags field being passed in. Why can't that be
> used to pass the XBF_NO_IOACCT flag? i.e:
>
Oops, I read over that too quickly as I saw it being passed into
alloc_page() and assumed it was for memory allocation flags. It is in
fact for buffer flags.. we just use xb_to_gfp() to select GFP_* flags
based on the buffer flags. I'll drop this patch and fold the
xfs_buf_read_cached() fixup into patch 2. Thanks.
Brian
> > ASSERT(bp->b_map_count == 1);
> > bp->b_bn = XFS_BUF_DADDR_NULL; /* always null for uncached buffers */
> > bp->b_maps[0].bm_bn = daddr;
> > - bp->b_flags |= XBF_READ;
> > + bp->b_flags |= XBF_READ | bflags;
>
> bp->b_flags |= XBF_READ;
> bp->b_flags |= (flags & XBF_NO_IOACCT);
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
>
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