linux-kernel - [PATCH 32/36] block: ioc_task

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 21 Feb 2012 17:46:59 -0800
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk, vgoyal@...hat.com
Cc:	ctalbott@...gle.com, rni@...gle.com, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 32/36] block: ioc_task_link() can't fail

ioc_task_link() is used to share %current's ioc on clone.  If
%current->io_context is set, %current is guaranteed to have refcount
on the ioc and, thus, ioc_task_link() can't fail.

Replace error checking in ioc_task_link() with WARN_ON_ONCE() and make
it just increment refcount and nr_tasks.

-v2: Description typo fix (Vivek).

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Vivek Goyal <vgoyal@...hat.com>
---
 include/linux/iocontext.h |   16 +++++-----------
 kernel/fork.c             |    5 ++---
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 1a30180..81a8870 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -120,18 +120,12 @@ struct io_context {
 	struct work_struct release_work;
 };
 
-static inline struct io_context *ioc_task_link(struct io_context *ioc)
+static inline void ioc_task_link(struct io_context *ioc)
 {
-	/*
-	 * if ref count is zero, don't allow sharing (ioc is going away, it's
-	 * a race).
-	 */
-	if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {
-		atomic_inc(&ioc->nr_tasks);
-		return ioc;
-	}
-
-	return NULL;
+	WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);
+	WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
+	atomic_long_inc(&ioc->refcount);
+	atomic_inc(&ioc->nr_tasks);
 }
 
 struct task_struct;
diff --git a/kernel/fork.c b/kernel/fork.c
index b77fd55..a1b6327 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -901,9 +901,8 @@ static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 	 * Share io context with parent, if CLONE_IO is set
 	 */
 	if (clone_flags & CLONE_IO) {
-		tsk->io_context = ioc_task_link(ioc);
-		if (unlikely(!tsk->io_context))
-			return -ENOMEM;
+		ioc_task_link(ioc);
+		tsk->io_context = ioc;
 	} else if (ioprio_valid(ioc->ioprio)) {
 		new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 		if (unlikely(!new_ioc))
-- 
1.7.7.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/