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Re: [PATCH 1/5] xfs: make superblock version checks reflect reality

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/5] xfs: make superblock version checks reflect reality
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 6 May 2014 01:29:48 -0700
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1399348559-19889-2-git-send-email-david@xxxxxxxxxxxxx>
References: <1399348559-19889-1-git-send-email-david@xxxxxxxxxxxxx> <1399348559-19889-2-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
> +/*
> + * The first XFS version we support is a v4 superblock with V2 directories.
> + */
> +static inline bool xfs_sb_good_v4_features(struct xfs_sb *sbp)
>  {
> +     if (!(sbp->sb_versionnum & XFS_SB_VERSION_DIRV2BIT))
> +             return false;
> +     /* check for unknown features in the fs */
> +     if ((sbp->sb_versionnum & ~XFS_SB_VERSION_OKBITS) ||

Given that sb_versionnum is a __uint16_t and XFS_SB_VERSION_OKBITS is
0xffff this will never evaluate to false and a sane compiler should warn
about it.  How about remove this check and XFS_SB_VERSION_OKBITS?

The various has_ macros are a bit confusing to me, as some explicitly
check for 5 superblocks, and some assume the caller handles them in
some way, but I think this is something we can leave for later cleanups.

>   * For example, for a bit defined as XFS_SB_VERSION2_FUNBIT, has a macro:
>   *
> - * SB_VERSION_HASFUNBIT(xfs_sb_t *sbp)
> + * SB_VERSION_HASFUNBIT(struct xfs_sb *sbp)

>   *   ((xfs_sb_version_hasmorebits(sbp) &&
>   *    ((sbp)->sb_features2 & XFS_SB_VERSION2_FUNBIT)
>   */

This should be updated to the lowe case convention inlines we've used
for a long time.  Or just removed as new features should go into v5

Modulo these minor bits:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>

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