Re: [PATCH 1/5] libxfs: Replace XFS_BUF_SET_PTR with xfs_buf_associate_memory

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Mar 06, 2018 at 03:54:08PM -0600, Eric Sandeen wrote:
> We test the return value of this macro, but it returns
> a side-effect which looks like failure.  Write a
> userspace-libxfs-specific version of xfs_buf_associate_memory
> to make this code a tad more like the kernel, with a proper
> return value to boot.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
>  libxfs/libxfs_io.h        | 12 ++++++++----
>  libxlog/xfs_log_recover.c |  4 ++--
>  2 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/libxfs/libxfs_io.h b/libxfs/libxfs_io.h
> index 6308a74..78b6780 100644
> --- a/libxfs/libxfs_io.h
> +++ b/libxfs/libxfs_io.h
> @@ -103,10 +103,6 @@ enum xfs_buf_flags_t {	/* b_flags bits */
>  #define XFS_BUF_SIZE(bp)		((bp)->b_bcount)
>  #define XFS_BUF_COUNT(bp)		((bp)->b_bcount)
>  #define XFS_BUF_TARGET(bp)		((bp)->b_dev)
> -#define XFS_BUF_SET_PTR(bp,p,cnt)	({	\
> -	(bp)->b_addr = (char *)(p);		\
> -	XFS_BUF_SET_COUNT(bp,cnt);		\
> -})
>  
>  #define XFS_BUF_SET_ADDR(bp,blk)	((bp)->b_bn = (blk))
>  #define XFS_BUF_SET_COUNT(bp,cnt)	((bp)->b_bcount = (cnt))
> @@ -230,4 +226,12 @@ xfs_buf_update_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
>  			 cksum_offset);
>  }
>  
> +static inline int
> +xfs_buf_associate_memory(struct xfs_buf *bp, void *mem, size_t len)
> +{
> +	bp->b_addr = mem;
> +	bp->b_bcount = len;

So long as len is never larger than an unsigned int (len is size_t,
b_bcount is unsigned int) this is fine. :)

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D


> +	return 0;
> +}
> +
>  #endif	/* __LIBXFS_IO_H__ */
> diff --git a/libxlog/xfs_log_recover.c b/libxlog/xfs_log_recover.c
> index 6bd000c..58d9182 100644
> --- a/libxlog/xfs_log_recover.c
> +++ b/libxlog/xfs_log_recover.c
> @@ -171,14 +171,14 @@ xlog_bread_offset(
>  	int		orig_len = bp->b_bcount;
>  	int		error, error2;
>  
> -	error = XFS_BUF_SET_PTR(bp, offset, BBTOB(nbblks));
> +	error = xfs_buf_associate_memory(bp, offset, BBTOB(nbblks));
>  	if (error)
>  		return error;
>  
>  	error = xlog_bread_noalign(log, blk_no, nbblks, bp);
>  
>  	/* must reset buffer pointer even on error */
> -	error2 = XFS_BUF_SET_PTR(bp, orig_offset, orig_len);
> +	error2 = xfs_buf_associate_memory(bp, orig_offset, orig_len);
>  	if (error)
>  		return error;
>  	return error2;
> -- 
> 1.8.3.1
> 
> 
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