linux-kernel - [PATCH v2] xfs_logprint: Fix super block buffer interpretation issue

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Message-Id: <20241011075253.2369053-1-chizhiling@163.com>
Date: Fri, 11 Oct 2024 15:52:53 +0800
From: Chi Zhiling <chizhiling@....com>
To: cem@...nel.org,
	djwong@...nel.org
Cc: linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Chi Zhiling <chizhiling@...inos.cn>
Subject: [PATCH v2] xfs_logprint: Fix super block buffer interpretation issue

From: Chi Zhiling <chizhiling@...inos.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@...nel.org>
Signed-off-by: Chi Zhiling <chizhiling@...inos.cn>
---
 logprint/log_misc.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/logprint/log_misc.c b/logprint/log_misc.c
index 8e86ac34..0da92744 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) be64_to_cpu(dsb->sb_icount),
+			       (unsigned long long) be64_to_cpu(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) be64_to_cpu(dsb->sb_fdblocks),
+			       (unsigned long long) be64_to_cpu(dsb->sb_frextents));
 		}
 		super_block = 0;
 	} else if (be32_to_cpu(*(__be32 *)(*ptr)) == XFS_AGI_MAGIC) {
-- 
2.43.0