Re: [PATCH v4] xfs_logprint: Fix super block buffer interpretation issue

Darrick J. Wong
2025-01-16T00:33:50Z

On Sun, Oct 13, 2024 at 12:29:52PM +0800, Chi Zhiling wrote:
> From: Chi Zhiling <chizhiling@kylinos.cn>
>
> When using xfs_logprint to interpret the buffer of the super block, the
> icount will always be 6360863066640355328 (0x5846534200001000). This is
> because the offset of icount is incorrect, causing xfs_logprint to
> misinterpret the MAGIC number as icount.
> This patch fixes the offset value of the SB counters in xfs_logprint.
>
> Before this patch:
> icount: 6360863066640355328 ifree: 5242880 fdblks: 0 frext: 0
>
> After this patch:
> icount: 10240 ifree: 4906 fdblks: 37 frext: 0
>
> Suggested-by: Darrick J. Wong <djwong@kernel.org>
> Suggested-by: Dave Chinner <david@fromorbit.com>
> Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> ---
> logprint/log_misc.c | 17 +++++------------

Hmm, I don't think this ever got merged...

but shouldn't log_print_all.c also get fixed? I think it has the same
pointer arithmetic problem that could be replaced by get_unaligned_be64
calls just like you did below.

--D

> 1 file changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/logprint/log_misc.c b/logprint/log_misc.c
> index 8e86ac34..803e4d2f 100644
> --- a/logprint/log_misc.c
> +++ b/logprint/log_misc.c
> @@ -282,22 +282,15 @@ xlog_print_trans_buffer(char **ptr, int len, int *i, int num_ops)
> if (be32_to_cpu(head->oh_len) < 4*8) {
> printf(_("Out of space\n"));
> } else {
> - __be64 a, b;
> + struct xfs_dsb *dsb = (struct xfs_dsb *) *ptr;
>
> printf("\n");
> - /*
> - * memmove because *ptr may not be 8-byte aligned
> - */
> - memmove(&a, *ptr, sizeof(__be64));
> - memmove(&b, *ptr+8, sizeof(__be64));
> printf(_("icount: %llu ifree: %llu "),
> - (unsigned long long) be64_to_cpu(a),
> - (unsigned long long) be64_to_cpu(b));
> - memmove(&a, *ptr+16, sizeof(__be64));
> - memmove(&b, *ptr+24, sizeof(__be64));
> + (unsigned long long) get_unaligned_be64(dsb->sb_icount),
> + (unsigned long long) get_unaligned_be64(dsb->sb_ifree));
> printf(_("fdblks: %llu frext: %llu\n"),
> - (unsigned long long) be64_to_cpu(a),
> - (unsigned long long) be64_to_cpu(b));
> + (unsigned long long) get_unaligned_be64(dsb->sb_fdblocks),
> + (unsigned long long) get_unaligned_be64(dsb->sb_frextents));
> }
> super_block = 0;
> } else if (be32_to_cpu(*(__be32 *)(*ptr)) == XFS_AGI_MAGIC) {
> --
>
> 2.43.0
>
>