From: Christoph Hellwig <hch@infradead.org>
To: Eric Sandeen <sandeen@redhat.com>
Cc: linux-xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH 1/2] xfs: don't take addresses of packed xfs_agfl_t member
Date: Wed, 29 Jan 2020 10:09:54 -0800 [thread overview]
Message-ID: <20200129180954.GC14855@infradead.org> (raw)
In-Reply-To: <09382ee9-8539-2f1d-bd4d-7256daf38a40@redhat.com>
On Wed, Jan 29, 2020 at 11:43:13AM -0600, Eric Sandeen wrote:
> gcc now warns about taking an address of a packed structure member.
>
> Work around this by using offsetof() instead.
>
> Thanks to bfoster for the suggestion and djwong for reiterating it.
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
>
> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
> index 1b7dcbae051c..7bfc8e2437e9 100644
> --- a/fs/xfs/libxfs/xfs_format.h
> +++ b/fs/xfs/libxfs/xfs_format.h
> @@ -787,7 +787,8 @@ typedef struct xfs_agi {
>
> #define XFS_BUF_TO_AGFL_BNO(mp, bp) \
> (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \
> - &(XFS_BUF_TO_AGFL(bp)->agfl_bno[0]) : \
> + (__be32 *)((char *)(bp)->b_addr + \
> + offsetof(struct xfs_agfl, agfl_bno)) : \
> (__be32 *)(bp)->b_addr)
Yikes. If we want to go down this route this really needs to become
an inline function (and fiven that it touches buffer is has no business
in xfs_format.h).
But I absolutely do not see the point. If agfl_bno was unalgined
so is adding the offsetoff. The warnings makes no sense, and there is
a good reason the kernel build turned it off.
next prev parent reply other threads:[~2020-01-29 18:09 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-29 17:41 [PATCH 0/2] xfs: don't take addresses of packed structures Eric Sandeen
2020-01-29 17:43 ` [PATCH 1/2] xfs: don't take addresses of packed xfs_agfl_t member Eric Sandeen
2020-01-29 18:09 ` Christoph Hellwig [this message]
2020-01-29 18:18 ` Eric Sandeen
2020-01-29 18:28 ` Christoph Hellwig
2020-01-29 18:46 ` Eric Sandeen
2020-01-29 17:45 ` [PATCH 2/2] xfs: don't take addresses of packed xfs_rmap_key Eric Sandeen
2020-01-29 17:56 ` Darrick J. Wong
2020-01-29 18:01 ` Eric Sandeen
2020-01-29 18:15 ` [PATCH 2/2 V2] xfs: don't take addresses of packed xfs_rmap_key member Eric Sandeen
2020-01-29 18:29 ` Christoph Hellwig
2020-01-29 18:31 ` Eric Sandeen
2020-01-29 18:35 ` [PATCH 2/2 V3] " Eric Sandeen
2020-01-29 18:36 ` Christoph Hellwig
2020-02-26 18:06 ` Darrick J. Wong
2020-02-26 18:21 ` Eric Sandeen
2020-02-26 18:45 ` Eric Sandeen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200129180954.GC14855@infradead.org \
--to=hch@infradead.org \
--cc=linux-xfs@vger.kernel.org \
--cc=sandeen@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox