[PATCH 5.16 0056/1017] cifs: we do not need a spinlock around the tree access during umount

Greg Kroah-Hartman
2022-04-05T11:05:00Z

From: Ronnie Sahlberg <lsahlber@redhat.com>

commit 9a14b65d590105d393b63f5320e1594edda7c672 upstream.

Remove the spinlock around the tree traversal as we are calling possibly
sleeping functions.
We do not need a spinlock here as there will be no modifications to this
tree at this point.

This prevents warnings like this to occur in dmesg:
[ 653.774996] BUG: sleeping function called from invalid context at kernel/loc\
king/mutex.c:280
[ 653.775088] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1827, nam\
e: umount
[ 653.775152] preempt_count: 1, expected: 0
[ 653.775191] CPU: 0 PID: 1827 Comm: umount Tainted: G W OE 5.17.0\
-rc7-00006-g4eb628dd74df #135
[ 653.775195] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-\
1.fc33 04/01/2014
[ 653.775197] Call Trace:
[ 653.775199] <TASK>
[ 653.775202] dump_stack_lvl+0x34/0x44
[ 653.775209] __might_resched.cold+0x13f/0x172
[ 653.775213] mutex_lock+0x75/0xf0
[ 653.775217] ? __mutex_lock_slowpath+0x10/0x10
[ 653.775220] ? _raw_write_lock_irq+0xd0/0xd0
[ 653.775224] ? dput+0x6b/0x360
[ 653.775228] cifs_kill_sb+0xff/0x1d0 [cifs]
[ 653.775285] deactivate_locked_super+0x85/0x130
[ 653.775289] cleanup_mnt+0x32c/0x4d0
[ 653.775292] ? path_umount+0x228/0x380
[ 653.775296] task_work_run+0xd8/0x180
[ 653.775301] exit_to_user_mode_loop+0x152/0x160
[ 653.775306] exit_to_user_mode_prepare+0x89/0xd0
[ 653.775315] syscall_exit_to_user_mode+0x12/0x30
[ 653.775322] do_syscall_64+0x48/0x90
[ 653.775326] entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 187af6e98b44e5d8f25e1d41a92db138eb54416f ("cifs: fix handlecache and multiuser")
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/cifsfs.c | 2 --
1 file changed, 2 deletions(-)

--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -265,7 +265,6 @@ static void cifs_kill_sb(struct super_bl
dput(cifs_sb->root);
cifs_sb->root = NULL;
}
- spin_lock(&cifs_sb->tlink_tree_lock);
node = rb_first(root);
while (node != NULL) {
tlink = rb_entry(node, struct tcon_link, tl_rbnode);
@@ -279,7 +278,6 @@ static void cifs_kill_sb(struct super_bl
mutex_unlock(&cfid->fid_mutex);
node = rb_next(node);
}
- spin_unlock(&cifs_sb->tlink_tree_lock);

kill_anon_super(sb);
cifs_umount(cifs_sb);