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From:   Stephen Boyd <swboyd@chromium.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        Petr Mladek <pmladek@suse.com>, Joe Perches <joe@perches.com>,
        Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH v3 1/4] slub: Restore slub_debug=- behavior
Date:   Tue,  1 Jun 2021 11:21:59 -0700
Message-Id: <20210601182202.3011020-2-swboyd@chromium.org>
In-Reply-To: <20210601182202.3011020-1-swboyd@chromium.org>
References: <20210601182202.3011020-1-swboyd@chromium.org>
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Passing slub_debug=- on the kernel commandline is supposed to disable
slub debugging. This is especially useful with CONFIG_SLUB_DEBUG_ON
where the default is to have slub debugging enabled in the build. Due to
some code reorganization this behavior was dropped, but the code to make
it work mostly stuck around. Restore the previous behavior by disabling
the static key when we parse the commandline and see that we're trying
to disable slub debugging.

Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Fixes: ca0cab65ea2b ("mm, slub: introduce static key for slub_debug()")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 mm/slub.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index 438fa8d4c970..2f53e8a9c28e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1396,6 +1396,8 @@ static int __init setup_slub_debug(char *str)
 out:
 	if (slub_debug != 0 || slub_debug_string)
 		static_branch_enable(&slub_debug_enabled);
+	else
+		static_branch_disable(&slub_debug_enabled);
 	if ((static_branch_unlikely(&init_on_alloc) ||
 	     static_branch_unlikely(&init_on_free)) &&
 	    (slub_debug & SLAB_POISON))
-- 
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