On Tue, 2018-01-30 at 12:31 -0500, Jeff Layton wrote:
> From: Jeff Layton <jlayton@xxxxxxxxxx>
>
> As Linus points out:
>
> The inode_cmp_iversion{+raw}() functions are pure and utter crap.
>
> Why?
>
> You say that they return 0/negative/positive, but they do so in a
> completely broken manner. They return that ternary value as the
> sequence number difference in a 's64', which means that if you
> actually care about that ternary value, and do the *sane* thing
> that
> the kernel-doc of the function implies is the right thing, you
> would
> do
>
> int cmp = inode_cmp_iversion(inode, old);
> if (cmp < 0 ...
>
> and as a result you get code that looks sane, but that doesn't
> actually *WORK* right.
>
> Since none of the callers actually care about the ternary value here,
> convert the inode_cmp_iversion{+raw} functions to just return a
> boolean
> value (false for matching, true for non-matching).
>
> This matches the existing use of these functions just fine, and makes
> it
> simple to convert them to return a ternary value in the future if we
> grow callers that need it.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> include/linux/iversion.h | 20 +++++++++-----------
> 1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/iversion.h b/include/linux/iversion.h
> index 858463fca249..ace32775c5f0 100644
> --- a/include/linux/iversion.h
> +++ b/include/linux/iversion.h
> @@ -309,13 +309,13 @@ inode_query_iversion(struct inode *inode)
> * @inode: inode to check
> * @old: old value to check against its i_version
> *
> - * Compare the current raw i_version counter with a previous one.
> Returns 0 if
> - * they are the same or non-zero if they are different.
> + * Compare the current raw i_version counter with a previous one.
> Returns false
> + * if they are the same or true if they are different.
> */
> -static inline s64
> +static inline bool
> inode_cmp_iversion_raw(const struct inode *inode, u64 old)
> {
> - return (s64)inode_peek_iversion_raw(inode) - (s64)old;
> + return inode_peek_iversion_raw(inode) != old;
> }
>
> /**
> @@ -323,19 +323,17 @@ inode_cmp_iversion_raw(const struct inode
> *inode, u64 old)
> * @inode: inode to check
> * @old: old value to check against its i_version
> *
> - * Compare an i_version counter with a previous one. Returns 0 if
> they are
> - * the same, a positive value if the one in the inode appears newer
> than @old,
> - * and a negative value if @old appears to be newer than the one in
> the
> - * inode.
> + * Compare an i_version counter with a previous one. Returns false
> if they are
> + * the same, and true if they are different.
> *
> * Note that we don't need to set the QUERIED flag in this case, as
> the value
> * in the inode is not being recorded for later use.
> */
>
> -static inline s64
> +static inline bool
> inode_cmp_iversion(const struct inode *inode, u64 old)
> {
> - return (s64)(inode_peek_iversion_raw(inode) &
> ~I_VERSION_QUERIED) -
> - (s64)(old << I_VERSION_QUERIED_SHIFT);
> + return (inode_peek_iversion_raw(inode) & ~I_VERSION_QUERIED)
> !=
> + (old << I_VERSION_QUERIED_SHIFT);
> }
Is there any reason why this couldn't just use inode_peek_iversion()
instead of having to both mask the output from
inode_peek_iversion_raw() and shift 'old'?
> #endif
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
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