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Re: [PATCH] Make __xfs_xattr_put_listen preperly report errors.

To: xfs@xxxxxxxxxxx
Subject: Re: [PATCH] Make __xfs_xattr_put_listen preperly report errors.
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Thu, 25 Aug 2016 16:36:30 -0500
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1471967653-2561-1-git-send-email-asavkov@xxxxxxxxxx>
References: <1471967653-2561-1-git-send-email-asavkov@xxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.2.0
On 8/23/16 10:54 AM, Artem Savkov wrote:
> Commit "xfs: only return -errno or success from attr ->put_listent" changes 
> the
> returnvalue of __xfs_xattr_put_listen to 0 in case when there is insufficient
> space in the buffer assuming that setting context->count to -1 would be 
> enough,
> but all of the ->put_listent callers only check seen_enough. This results in
> a failed assertion:
> XFS: Assertion failed: context->count >= 0, file: fs/xfs/xfs_xattr.c, line: 
> 175
> in insufficient buffer size case.

Oof.  I remember spending a lot of time trying to track down all
of these cases.  It seems overly complex and obscure.  :(

I'll try to find time to dig through it again; offhand it doesn't
seem like "count = -1" means anything to anyone except in an
ASSERT check?

Thanks,
-Eric


> Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_xattr.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
> index ea62245..6290093 100644
> --- a/fs/xfs/xfs_xattr.c
> +++ b/fs/xfs/xfs_xattr.c
> @@ -147,6 +147,7 @@ __xfs_xattr_put_listent(
>       arraytop = context->count + prefix_len + namelen + 1;
>       if (arraytop > context->firstu) {
>               context->count = -1;    /* insufficient space */
> +             context->seen_enough = 1;
>               return 0;
>       }
>       offset = (char *)context->alist + context->count;
> 

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