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

Chi Zhiling
2025-01-16T01:38:49Z

On 2025/1/16 08:33, Darrick J. Wong wrote:
> 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.

Indeed, the same issue also exists in log_print_all.c. I will fix it in
the next push.

Thanks,
Chi Zhiling

>
> --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
>>
>>