From: Thomas Gleixner Date: Sun, 19 Jul 2009 08:44:27 -0500 Subject: fs: namespace preemption fix Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.5-rt3.tar.xz On RT we cannot loop with preemption disabled here as mnt_make_readonly() might have been preempted. We can safely enable preemption while waiting for MNT_WRITE_HOLD to be cleared. Safe on !RT as well. Signed-off-by: Thomas Gleixner --- fs/namespace.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/namespace.c +++ b/fs/namespace.c @@ -353,8 +353,11 @@ int __mnt_want_write(struct vfsmount *m) * incremented count after it has set MNT_WRITE_HOLD. */ smp_mb(); - while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) + while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) { + preempt_enable(); cpu_relax(); + preempt_disable(); + } /* * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will * be set to match its requirements. So we must not load that until