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Remove misguided HAVE_MUTEX_OWNER check, take 2

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It is just plain unsafe to peek inside in-kernel
mutex structure and make assumptions about what kernel
does with those internal fields like owner.

Kernel is all too happy to stop doing the expected things
like tracing lock owner once you load a tainted module
like spl/zfs that is not GPL.

As such you will get instant assertion failures like this:

  VERIFY3(((*(volatile typeof((&((&zo->zo_lock)->m_mutex))->owner) *)&
      ((&((&zo->zo_lock)->m_mutex))->owner))) ==
     ((void *)0)) failed (ffff88030be28500 == (null))
  PANIC at zfs_onexit.c:104:zfs_onexit_destroy()
  Showing stack for process 3626
  CPU: 0 PID: 3626 Comm: mkfs.lustre Tainted: P OE ------------ 3.10.0-debug #1
  Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
  Call Trace:
  dump_stack+0x19/0x1b
  spl_dumpstack+0x44/0x50 [spl]
  spl_panic+0xbf/0xf0 [spl]
  zfs_onexit_destroy+0x17c/0x280 [zfs]
  zfsdev_release+0x48/0xd0 [zfs]

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Reviewed-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Closes #639
Closes #632
This commit is contained in:
Oleg Drokin 2017-08-02 14:45:16 -04:00 committed by Brian Behlendorf
parent 261a3151e1
commit 98cdcb8286
2 changed files with 0 additions and 45 deletions
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30
config/spl-build.m4
View File

@ -49,7 +49,6 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
SPL_AC_USLEEP_RANGE
SPL_AC_KMEM_CACHE_ALLOCFLAGS
SPL_AC_WAIT_ON_BIT
SPL_AC_MUTEX_OWNER
SPL_AC_INODE_LOCK
SPL_AC_GROUP_INFO_GID
SPL_AC_KMEM_CACHE_CREATE_USERCOPY
@ -1562,35 +1561,6 @@ AC_DEFUN([SPL_AC_WAIT_ON_BIT], [
])
])
dnl #
dnl # Check whether mutex has owner with task_struct type.
dnl #
dnl # Note that before Linux 3.0, mutex owner is of type thread_info.
dnl #
dnl # Note that in Linux 3.18, the condition for owner is changed from
dnl # defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP) to
dnl # defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER)
dnl #
AC_DEFUN([SPL_AC_MUTEX_OWNER], [
AC_MSG_CHECKING([whether mutex has owner])
tmp_flags="$EXTRA_KCFLAGS"
EXTRA_KCFLAGS="-Werror"
SPL_LINUX_TRY_COMPILE([
#include <linux/mutex.h>
#include <linux/spinlock.h>
],[
DEFINE_MUTEX(m);
struct task_struct *t __attribute__ ((unused));
t = m.owner;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_MUTEX_OWNER, 1, [yes])
],[
AC_MSG_RESULT(no)
])
EXTRA_KCFLAGS="$tmp_flags"
])
dnl #
dnl # 4.7 API change
dnl # i_mutex is changed to i_rwsem. Instead of directly using

15
include/sys/mutex.h
View File

@ -40,10 +40,7 @@ typedef enum {
typedef struct {
struct mutex m_mutex;
spinlock_t m_lock; /* used for serializing mutex_exit */
#ifndef HAVE_MUTEX_OWNER
/* only when kernel doesn't have owner */
kthread_t *m_owner;
#endif
#ifdef CONFIG_LOCKDEP
kmutex_type_t m_type;
#endif /* CONFIG_LOCKDEP */
@ -54,28 +51,16 @@ typedef struct {
static inline void
spl_mutex_set_owner(kmutex_t *mp)
{
/*
* kernel will handle its owner, so we don't need to do anything if it
* is defined.
*/
#ifndef HAVE_MUTEX_OWNER
mp->m_owner = current;
#endif
}
static inline void
spl_mutex_clear_owner(kmutex_t *mp)
{
#ifndef HAVE_MUTEX_OWNER
mp->m_owner = NULL;
#endif
}
#ifdef HAVE_MUTEX_OWNER
#define mutex_owner(mp) (ACCESS_ONCE(MUTEX(mp)->owner))
#else
#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner))
#endif
#define mutex_owned(mp) (mutex_owner(mp) == current)
#define MUTEX_HELD(mp) mutex_owned(mp)
#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))