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Re: [PATCH 1/8] xfs: factor DIO write mapping from get_blocks

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/8] xfs: factor DIO write mapping from get_blocks
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue, 14 Apr 2015 10:23:46 -0400
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1428996411-1507-2-git-send-email-david@xxxxxxxxxxxxx>
References: <1428996411-1507-1-git-send-email-david@xxxxxxxxxxxxx> <1428996411-1507-2-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Tue, Apr 14, 2015 at 05:26:44PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> Clarify and separate the buffer mapping logic so that the direct IO mapping is
> not tangled up in propagating the extent status to teh mapping buffer. This
> makes it easier to extend the direct IO mapping to use an ioend in future.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_aops.c | 36 +++++++++++++++++++++++-------------
>  1 file changed, 23 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 3a9b7a1..5f7ddd5 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1233,6 +1233,22 @@ xfs_vm_releasepage(
>       return try_to_free_buffers(page);
>  }
>  
> +/*
> + * do all the direct IO specific mapping buffer manipulation here.
> + */
> +static void
> +xfs_map_direct(
> +     struct inode            *inode,
> +     struct buffer_head      *bh_result,
> +     struct xfs_bmbt_irec    *imap,
> +     xfs_off_t               offset)
> +{
> +     if (ISUNWRITTEN(imap)) {
> +             bh_result->b_private = inode;
> +             set_buffer_defer_completion(bh_result);
> +     }
> +}
> +
>  STATIC int
>  __xfs_get_blocks(
>       struct inode            *inode,
> @@ -1332,20 +1348,14 @@ __xfs_get_blocks(
>       }
>  
>       if (imap.br_startblock != HOLESTARTBLOCK &&
> -         imap.br_startblock != DELAYSTARTBLOCK) {
> -             /*
> -              * For unwritten extents do not report a disk address on
> -              * the read case (treat as if we're reading into a hole).
> -              */

Can we keep this comment and move it before this block?

Brian

> -             if (create || !ISUNWRITTEN(&imap))
> -                     xfs_map_buffer(inode, bh_result, &imap, offset);
> -             if (create && ISUNWRITTEN(&imap)) {
> -                     if (direct) {
> -                             bh_result->b_private = inode;
> -                             set_buffer_defer_completion(bh_result);
> -                     }
> +         imap.br_startblock != DELAYSTARTBLOCK &&
> +         (create || !ISUNWRITTEN(&imap))) {
> +             xfs_map_buffer(inode, bh_result, &imap, offset);
> +             if (ISUNWRITTEN(&imap))
>                       set_buffer_unwritten(bh_result);
> -             }
> +             /* direct IO needs special help */
> +             if (create && direct)
> +                     xfs_map_direct(inode, bh_result, &imap, offset);
>       }
>  
>       /*
> -- 
> 2.0.0
> 
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