linux-kernel - [PATCH] [RFC] mm/page_ref, crypto/async_pq: don't put_page from _

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Date:	Sun, 28 Feb 2016 22:57:23 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org
Cc:	linux-arm-kernel@...ts.infradead.org,
	Michal Nazarewicz <mina86@...a86.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Dan Williams <dan.j.williams@...el.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] [RFC] mm/page_ref, crypto/async_pq: don't put_page from __exit

The addition of tracepoints to the page reference tracking had an
unfortunate side-effect in at least one driver that calls put_page
from its exit function, resulting in a link error:

`.exit.text' referenced in section `__jump_table' of crypto/built-in.o: defined in discarded section `.exit.text' of crypto/built-in.o

I could not come up with a nice solution that ignores __jump_table
entries in discarded code, so we probably now have to treat this
as something a driver is not allowed to do. Removing the __exit
annotation avoids the problem in this particular driver, but the
same problem could come back any time in other code.

On a related problem regarding the runtime patching for SMP
operations on ARM uniprocessor systems, we resorted to not
drop the .exit section at link time, but that doesn't seem
appropriate here.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Fixes: 0f80830dd044 ("mm/page_ref: add tracepoint to track down page reference manipulation")
---
 crypto/async_tx/async_pq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c
index c0748bbd4c08..be167145aa55 100644
--- a/crypto/async_tx/async_pq.c
+++ b/crypto/async_tx/async_pq.c
@@ -442,7 +442,7 @@ static int __init async_pq_init(void)
 	return -ENOMEM;
 }
 
-static void __exit async_pq_exit(void)
+static void async_pq_exit(void)
 {
 	put_page(pq_scribble_page);
 }
-- 
2.7.0