linux-kernel - Re: [PATCH] xfs: fix an undefined behaviour in _da3_path

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Message-ID: <20200225180725.GA29862@infradead.org>
Date:   Tue, 25 Feb 2020 10:07:25 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Qian Cai <cai@....pw>
Cc:     darrick.wong@...cle.com, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: fix an undefined behaviour in _da3_path_shift

I think we code do this a tad more cleaner, something like:

diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index 875e04f82541..542a4edfcf54 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -1986,7 +1986,8 @@ xfs_da3_path_shift(
 	ASSERT(path != NULL);
 	ASSERT((path->active > 0) && (path->active < XFS_DA_NODE_MAXDEPTH));
 	level = (path->active-1) - 1;	/* skip bottom layer in path */
-	for (blk = &path->blk[level]; level >= 0; blk--, level--) {
+	for ( ; level >= 0; level--) {
+		blk = &path->blk[level];
 		xfs_da3_node_hdr_from_disk(dp->i_mount, &nodehdr,
 					   blk->bp->b_addr);