| Message ID | 20181212155055.1269-1-mhocko@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] mm, memcg: fix reclaim deadlock with writeback | expand |
On Wed, Dec 12, 2018 at 7:51 AM Michal Hocko <mhocko@kernel.org> wrote: > > From: Michal Hocko <mhocko@suse.com> > > Liu Bo has experienced a deadlock between memcg (legacy) reclaim and the > ext4 writeback > task1: > [<ffffffff811aaa52>] wait_on_page_bit+0x82/0xa0 > [<ffffffff811c5777>] shrink_page_list+0x907/0x960 > [<ffffffff811c6027>] shrink_inactive_list+0x2c7/0x680 > [<ffffffff811c6ba4>] shrink_node_memcg+0x404/0x830 > [<ffffffff811c70a8>] shrink_node+0xd8/0x300 > [<ffffffff811c73dd>] do_try_to_free_pages+0x10d/0x330 > [<ffffffff811c7865>] try_to_free_mem_cgroup_pages+0xd5/0x1b0 > [<ffffffff8122df2d>] try_charge+0x14d/0x720 > [<ffffffff812320cc>] memcg_kmem_charge_memcg+0x3c/0xa0 > [<ffffffff812321ae>] memcg_kmem_charge+0x7e/0xd0 > [<ffffffff811b68a8>] __alloc_pages_nodemask+0x178/0x260 > [<ffffffff8120bff5>] alloc_pages_current+0x95/0x140 > [<ffffffff81074247>] pte_alloc_one+0x17/0x40 > [<ffffffff811e34de>] __pte_alloc+0x1e/0x110 > [<ffffffffa06739de>] alloc_set_pte+0x5fe/0xc20 > [<ffffffff811e5d93>] do_fault+0x103/0x970 > [<ffffffff811e6e5e>] handle_mm_fault+0x61e/0xd10 > [<ffffffff8106ea02>] __do_page_fault+0x252/0x4d0 > [<ffffffff8106ecb0>] do_page_fault+0x30/0x80 > [<ffffffff8171bce8>] page_fault+0x28/0x30 > [<ffffffffffffffff>] 0xffffffffffffffff > > task2: > [<ffffffff811aadc6>] __lock_page+0x86/0xa0 > [<ffffffffa02f1e47>] mpage_prepare_extent_to_map+0x2e7/0x310 [ext4] > [<ffffffffa08a2689>] ext4_writepages+0x479/0xd60 > [<ffffffff811bbede>] do_writepages+0x1e/0x30 > [<ffffffff812725e5>] __writeback_single_inode+0x45/0x320 > [<ffffffff81272de2>] writeback_sb_inodes+0x272/0x600 > [<ffffffff81273202>] __writeback_inodes_wb+0x92/0xc0 > [<ffffffff81273568>] wb_writeback+0x268/0x300 > [<ffffffff81273d24>] wb_workfn+0xb4/0x390 > [<ffffffff810a2f19>] process_one_work+0x189/0x420 > [<ffffffff810a31fe>] worker_thread+0x4e/0x4b0 > [<ffffffff810a9786>] kthread+0xe6/0x100 > [<ffffffff8171a9a1>] ret_from_fork+0x41/0x50 > [<ffffffffffffffff>] 0xffffffffffffffff > > He adds > : task1 is waiting for the PageWriteback bit of the page that task2 has > : collected in mpd->io_submit->io_bio, and tasks2 is waiting for the LOCKED > : bit the page which tasks1 has locked. > > More precisely task1 is handling a page fault and it has a page locked > while it charges a new page table to a memcg. That in turn hits a memory > limit reclaim and the memcg reclaim for legacy controller is waiting on > the writeback but that is never going to finish because the writeback > itself is waiting for the page locked in the #PF path. So this is > essentially ABBA deadlock. > > Waiting for the writeback in legacy memcg controller is a workaround > for pre-mature OOM killer invocations because there is no dirty IO > throttling available for the controller. There is no easy way around > that unfortunately. Therefore fix this specific issue by pre-allocating > the page table outside of the page lock. We have that handy > infrastructure for that already so simply reuse the fault-around pattern > which already does this. Michal, can you please add the following para in the commit message as well which was in the first version. This fact should be documented at least in the commit message. > > There are probably other hidden __GFP_ACCOUNT | GFP_KERNEL allocations > from under a fs page locked but they should be really rare. I am not > aware of a better solution unfortunately. > thanks, Shakeel
On Wed, Dec 12, 2018 at 04:50:55PM +0100, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Liu Bo has experienced a deadlock between memcg (legacy) reclaim and the > ext4 writeback > task1: > [<ffffffff811aaa52>] wait_on_page_bit+0x82/0xa0 > [<ffffffff811c5777>] shrink_page_list+0x907/0x960 > [<ffffffff811c6027>] shrink_inactive_list+0x2c7/0x680 > [<ffffffff811c6ba4>] shrink_node_memcg+0x404/0x830 > [<ffffffff811c70a8>] shrink_node+0xd8/0x300 > [<ffffffff811c73dd>] do_try_to_free_pages+0x10d/0x330 > [<ffffffff811c7865>] try_to_free_mem_cgroup_pages+0xd5/0x1b0 > [<ffffffff8122df2d>] try_charge+0x14d/0x720 > [<ffffffff812320cc>] memcg_kmem_charge_memcg+0x3c/0xa0 > [<ffffffff812321ae>] memcg_kmem_charge+0x7e/0xd0 > [<ffffffff811b68a8>] __alloc_pages_nodemask+0x178/0x260 > [<ffffffff8120bff5>] alloc_pages_current+0x95/0x140 > [<ffffffff81074247>] pte_alloc_one+0x17/0x40 > [<ffffffff811e34de>] __pte_alloc+0x1e/0x110 > [<ffffffffa06739de>] alloc_set_pte+0x5fe/0xc20 > [<ffffffff811e5d93>] do_fault+0x103/0x970 > [<ffffffff811e6e5e>] handle_mm_fault+0x61e/0xd10 > [<ffffffff8106ea02>] __do_page_fault+0x252/0x4d0 > [<ffffffff8106ecb0>] do_page_fault+0x30/0x80 > [<ffffffff8171bce8>] page_fault+0x28/0x30 > [<ffffffffffffffff>] 0xffffffffffffffff > > task2: > [<ffffffff811aadc6>] __lock_page+0x86/0xa0 > [<ffffffffa02f1e47>] mpage_prepare_extent_to_map+0x2e7/0x310 [ext4] > [<ffffffffa08a2689>] ext4_writepages+0x479/0xd60 > [<ffffffff811bbede>] do_writepages+0x1e/0x30 > [<ffffffff812725e5>] __writeback_single_inode+0x45/0x320 > [<ffffffff81272de2>] writeback_sb_inodes+0x272/0x600 > [<ffffffff81273202>] __writeback_inodes_wb+0x92/0xc0 > [<ffffffff81273568>] wb_writeback+0x268/0x300 > [<ffffffff81273d24>] wb_workfn+0xb4/0x390 > [<ffffffff810a2f19>] process_one_work+0x189/0x420 > [<ffffffff810a31fe>] worker_thread+0x4e/0x4b0 > [<ffffffff810a9786>] kthread+0xe6/0x100 > [<ffffffff8171a9a1>] ret_from_fork+0x41/0x50 > [<ffffffffffffffff>] 0xffffffffffffffff > > He adds > : task1 is waiting for the PageWriteback bit of the page that task2 has > : collected in mpd->io_submit->io_bio, and tasks2 is waiting for the LOCKED > : bit the page which tasks1 has locked. > > More precisely task1 is handling a page fault and it has a page locked > while it charges a new page table to a memcg. That in turn hits a memory > limit reclaim and the memcg reclaim for legacy controller is waiting on > the writeback but that is never going to finish because the writeback > itself is waiting for the page locked in the #PF path. So this is > essentially ABBA deadlock. Thanks for the patch, Michal. Could you please append the followings (quoted from your reply in other thread)? It'd be much easier for reviewers to pick up what was happening. ----------------------------------------------------------------- lock_page(B) SetPageWriteback(B) unlock_page(B) lock_page(A) lock_page(A) pte_alloc_pne shrink_page_list wait_on_page_writeback(B) SetPageWriteback(A) unlock_page(A) # flush A, B to clear the writeback ----------------------------------------------------------------- thanks, -liubo > > Waiting for the writeback in legacy memcg controller is a workaround > for pre-mature OOM killer invocations because there is no dirty IO > throttling available for the controller. There is no easy way around > that unfortunately. Therefore fix this specific issue by pre-allocating > the page table outside of the page lock. We have that handy > infrastructure for that already so simply reuse the fault-around pattern > which already does this. > > Reported-and-Debugged-by: Liu Bo <bo.liu@linux.alibaba.com> > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- > mm/memory.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 4ad2d293ddc2..bb78e90a9b70 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2993,6 +2993,17 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) > struct vm_area_struct *vma = vmf->vma; > vm_fault_t ret; > > + /* > + * Preallocate pte before we take page_lock because this might lead to > + * deadlocks for memcg reclaim which waits for pages under writeback. > + */ > + if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) { > + vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm, vmf->address); > + if (!vmf->prealloc_pte) > + return VM_FAULT_OOM; > + smp_wmb(); /* See comment in __pte_alloc() */ > + } > + > ret = vma->vm_ops->fault(vmf); > if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | > VM_FAULT_DONE_COW))) > -- > 2.19.2
diff --git a/mm/memory.c b/mm/memory.c index 4ad2d293ddc2..bb78e90a9b70 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2993,6 +2993,17 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; vm_fault_t ret; + /* + * Preallocate pte before we take page_lock because this might lead to + * deadlocks for memcg reclaim which waits for pages under writeback. + */ + if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) { + vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm, vmf->address); + if (!vmf->prealloc_pte) + return VM_FAULT_OOM; + smp_wmb(); /* See comment in __pte_alloc() */ + } + ret = vma->vm_ops->fault(vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | VM_FAULT_DONE_COW)))