mm/mmu_notifier: allocate mmu_notifier in advance
While allocating mmu_notifier with parameter GFP_KERNEL, swap would start
to work in case of tight available memory. Eventually, that would lead to
a deadlock while the swap deamon swaps anonymous pages. It was caused by
commit e0f3c3f78da29b ("mm/mmu_notifier: init notifier if necessary").
=================================
[ INFO: inconsistent lock state ]
3.7.0-rc1+ #518 Not tainted
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
kswapd0/35 [HC0[0]:SC0[0]:HE1:SE1] takes:
(&mapping->i_mmap_mutex){+.+.?.}, at: page_referenced+0x9c/0x2e0
{RECLAIM_FS-ON-W} state was registered at:
mark_held_locks+0x86/0x150
lockdep_trace_alloc+0x67/0xc0
kmem_cache_alloc_trace+0x33/0x230
do_mmu_notifier_register+0x87/0x180
mmu_notifier_register+0x13/0x20
kvm_dev_ioctl+0x428/0x510
do_vfs_ioctl+0x98/0x570
sys_ioctl+0x91/0xb0
system_call_fastpath+0x16/0x1b
irq event stamp: 825
hardirqs last enabled at (825): _raw_spin_unlock_irq+0x30/0x60
hardirqs last disabled at (824): _raw_spin_lock_irq+0x19/0x80
softirqs last enabled at (0): copy_process+0x630/0x17c0
softirqs last disabled at (0): (null)
...
Simply back out the above commit, which was a small performance
optimization.
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Reported-by: Andrea Righi <andrea@betterlinux.com>
Tested-by: Andrea Righi <andrea@betterlinux.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Sagi Grimberg <sagig@mellanox.co.il>
Cc: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 479a1e7..8a5ac8c 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -196,28 +196,28 @@
BUG_ON(atomic_read(&mm->mm_users) <= 0);
/*
- * Verify that mmu_notifier_init() already run and the global srcu is
- * initialized.
- */
+ * Verify that mmu_notifier_init() already run and the global srcu is
+ * initialized.
+ */
BUG_ON(!srcu.per_cpu_ref);
+ ret = -ENOMEM;
+ mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
+ if (unlikely(!mmu_notifier_mm))
+ goto out;
+
if (take_mmap_sem)
down_write(&mm->mmap_sem);
ret = mm_take_all_locks(mm);
if (unlikely(ret))
- goto out;
+ goto out_clean;
if (!mm_has_notifiers(mm)) {
- mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm),
- GFP_KERNEL);
- if (unlikely(!mmu_notifier_mm)) {
- ret = -ENOMEM;
- goto out_of_mem;
- }
INIT_HLIST_HEAD(&mmu_notifier_mm->list);
spin_lock_init(&mmu_notifier_mm->lock);
mm->mmu_notifier_mm = mmu_notifier_mm;
+ mmu_notifier_mm = NULL;
}
atomic_inc(&mm->mm_count);
@@ -233,12 +233,12 @@
hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
spin_unlock(&mm->mmu_notifier_mm->lock);
-out_of_mem:
mm_drop_all_locks(mm);
-out:
+out_clean:
if (take_mmap_sem)
up_write(&mm->mmap_sem);
-
+ kfree(mmu_notifier_mm);
+out:
BUG_ON(atomic_read(&mm->mm_users) <= 0);
return ret;
}