+ ocfs2-kill-osb-system_file_mutex-lock.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: ocfs2: kill osb->system_file_mutex lock
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ocfs2-kill-osb-system_file_mutex-lock.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-kill-osb-system_file_mutex-lock.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Subject: ocfs2: kill osb->system_file_mutex lock
Date: Sun, 22 Jun 2025 00:56:46 +0900

Since calling _ocfs2_get_system_file_inode() twice with the same arguments
returns the same address, there is no need to serialize
_ocfs2_get_system_file_inode() using osb->system_file_mutex lock.

Kill osb->system_file_mutex lock in order to avoid AB-BA deadlock. 
cmpxchg() will be sufficient for avoiding the inode refcount leak problem
which commit 43b10a20372d ("ocfs2: avoid system inode ref confusion by
adding mutex lock") tried to address.

Link: https://lkml.kernel.org/r/934355dd-a0b1-4e53-93ac-0a7ae7458051@I-love.SAKURA.ne.jp
Reported-by: Diogo Jahchan Koike <djahchankoike@gmail.com>
Closes: https://lkml.kernel.org/r/000000000000ff2d7a0620381afe@google.com
Fixes: 43b10a20372d ("ocfs2: avoid system inode ref confusion by adding mutex lock")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: jiangyiwen <jiangyiwen@huawei.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/ocfs2.h   |    2 --
 fs/ocfs2/super.c   |    2 --
 fs/ocfs2/sysfile.c |    9 +++------
 3 files changed, 3 insertions(+), 10 deletions(-)

--- a/fs/ocfs2/ocfs2.h~ocfs2-kill-osb-system_file_mutex-lock
+++ a/fs/ocfs2/ocfs2.h
@@ -494,8 +494,6 @@ struct ocfs2_super
 	struct rb_root	osb_rf_lock_tree;
 	struct ocfs2_refcount_tree *osb_ref_tree_lru;
 
-	struct mutex system_file_mutex;
-
 	/*
 	 * OCFS2 needs to schedule several different types of work which
 	 * require cluster locking, disk I/O, recovery waits, etc. Since these
--- a/fs/ocfs2/super.c~ocfs2-kill-osb-system_file_mutex-lock
+++ a/fs/ocfs2/super.c
@@ -1997,8 +1997,6 @@ static int ocfs2_initialize_super(struct
 	spin_lock_init(&osb->osb_xattr_lock);
 	ocfs2_init_steal_slots(osb);
 
-	mutex_init(&osb->system_file_mutex);
-
 	atomic_set(&osb->alloc_stats.moves, 0);
 	atomic_set(&osb->alloc_stats.local_data, 0);
 	atomic_set(&osb->alloc_stats.bitmap_data, 0);
--- a/fs/ocfs2/sysfile.c~ocfs2-kill-osb-system_file_mutex-lock
+++ a/fs/ocfs2/sysfile.c
@@ -98,11 +98,9 @@ struct inode *ocfs2_get_system_file_inod
 	} else
 		arr = get_local_system_inode(osb, type, slot);
 
-	mutex_lock(&osb->system_file_mutex);
 	if (arr && ((inode = *arr) != NULL)) {
 		/* get a ref in addition to the array ref */
 		inode = igrab(inode);
-		mutex_unlock(&osb->system_file_mutex);
 		BUG_ON(!inode);
 
 		return inode;
@@ -112,11 +110,10 @@ struct inode *ocfs2_get_system_file_inod
 	inode = _ocfs2_get_system_file_inode(osb, type, slot);
 
 	/* add one more if putting into array for first time */
-	if (arr && inode) {
-		*arr = igrab(inode);
-		BUG_ON(!*arr);
+	if (inode && arr && !*arr && !cmpxchg(&(*arr), NULL, inode)) {
+		inode = igrab(inode);
+		BUG_ON(!inode);
 	}
-	mutex_unlock(&osb->system_file_mutex);
 	return inode;
 }
 
_

Patches currently in -mm which might be from penguin-kernel@I-love.SAKURA.ne.jp are

ocfs2-kill-osb-system_file_mutex-lock.patch