[PATCH] xfs: fix endianness issue in xfs_ag_shrink_space

From: "Darrick J. Wong" <djwong@kernel.org>
To: xfs <linux-xfs@vger.kernel.org>
Subject: [PATCH] xfs: fix endianness issue in xfs_ag_shrink_space
Date: Mon, 21 Jun 2021 15:34:36 -0700	[thread overview]
Message-ID: <20210621223436.GF3619569@locust> (raw)

From: Darrick J. Wong <djwong@kernel.org>

The AGI buffer is in big-endian format, so we must convert the
endianness to CPU format to do any comparisons.

Fixes: 46141dc891f7 ("xfs: introduce xfs_ag_shrink_space()")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_ag.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
index c68a36688474..afff2ab7e9f1 100644
--- a/fs/xfs/libxfs/xfs_ag.c
+++ b/fs/xfs/libxfs/xfs_ag.c
@@ -510,6 +510,7 @@ xfs_ag_shrink_space(
 	struct xfs_buf		*agibp, *agfbp;
 	struct xfs_agi		*agi;
 	struct xfs_agf		*agf;
+	xfs_agblock_t		aglen;
 	int			error, err2;
 
 	ASSERT(agno == mp->m_sb.sb_agcount - 1);
@@ -524,14 +525,14 @@ xfs_ag_shrink_space(
 		return error;
 
 	agf = agfbp->b_addr;
+	aglen = be32_to_cpu(agi->agi_length);
 	/* some extra paranoid checks before we shrink the ag */
 	if (XFS_IS_CORRUPT(mp, agf->agf_length != agi->agi_length))
 		return -EFSCORRUPTED;
-	if (delta >= agi->agi_length)
+	if (delta >= aglen)
 		return -EINVAL;
 
-	args.fsbno = XFS_AGB_TO_FSB(mp, agno,
-				    be32_to_cpu(agi->agi_length) - delta);
+	args.fsbno = XFS_AGB_TO_FSB(mp, agno, aglen - delta);
 
 	/*
 	 * Disable perag reservations so it doesn't cause the allocation request
