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Re: [PATCH 11/14] xfs: remote attribute tail zeroing does too much

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 11/14] xfs: remote attribute tail zeroing does too much
From: Ben Myers <bpm@xxxxxxx>
Date: Mon, 20 May 2013 18:01:21 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1369007481-15185-12-git-send-email-david@xxxxxxxxxxxxx>
References: <1369007481-15185-1-git-send-email-david@xxxxxxxxxxxxx> <1369007481-15185-12-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, May 20, 2013 at 09:51:18AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> When an attribute data does not fill then entire remote block, we
> zero the remaining part of the buffer. This, however, needs to take
> into account that the buffer has a header, and so the offset where
> zeroing starts and the length of zeroing need to take this into
> account. Otherwise we end up with zeros over the end of the
> attribute value when CRCs are enabled.
> 
> While there, make sure we only ask to map an extent that covers the
> remaining range of the attribute, rather than asking every time for
> the full length of remote data. If the remote attribute blocks are
> contiguous with other parts of the attribute tree, it will map those
> blocks as well and we can potentially zero them incorrectly. We can
> also get buffer size mistmatches when trying to read or remove the
> remote attribute, and this can lead to not finding the correct
> buffer when looking it up in cache.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_attr_remote.c |   37 ++++++++++++++++++-------------------
>  1 file changed, 18 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/xfs/xfs_attr_remote.c b/fs/xfs/xfs_attr_remote.c
> index bcdc07c..e207bf0 100644
> --- a/fs/xfs/xfs_attr_remote.c
> +++ b/fs/xfs/xfs_attr_remote.c
> @@ -296,10 +296,7 @@ xfs_attr_rmtval_set(
>        * and we may not need that many, so we have to handle this when
>        * allocating the blocks below. 
>        */
> -     if (!crcs)
> -             blkcnt = XFS_B_TO_FSB(mp, args->valuelen);
> -     else
> -             blkcnt = xfs_attr3_rmt_blocks(mp, args->valuelen);
> +     blkcnt = xfs_attr3_rmt_blocks(mp, args->valuelen);

Oh.  There you have it.  Nevermind.

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