From c5f88bd29ab42d5d1e77085b5f69d5c6da20324e Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Tue, 2 Aug 2016 14:02:22 -0700 Subject: mm: fail prefaulting if page table allocation fails I ran into this: BUG: sleeping function called from invalid context at mm/page_alloc.c:3784 in_atomic(): 0, irqs_disabled(): 0, pid: 1434, name: trinity-c1 2 locks held by trinity-c1/1434: #0: (&mm->mmap_sem){......}, at: [] __do_page_fault+0x1ce/0x8f0 #1: (rcu_read_lock){......}, at: [] filemap_map_pages+0xd6/0xdd0 CPU: 0 PID: 1434 Comm: trinity-c1 Not tainted 4.7.0+ #58 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0x65/0x84 panic+0x185/0x2dd ___might_sleep+0x51c/0x600 __might_sleep+0x90/0x1a0 __alloc_pages_nodemask+0x5b1/0x2160 alloc_pages_current+0xcc/0x370 pte_alloc_one+0x12/0x90 __pte_alloc+0x1d/0x200 alloc_set_pte+0xe3e/0x14a0 filemap_map_pages+0x42b/0xdd0 handle_mm_fault+0x17d5/0x28b0 __do_page_fault+0x310/0x8f0 trace_do_page_fault+0x18d/0x310 do_async_page_fault+0x27/0xa0 async_page_fault+0x28/0x30 The important bits from the above is that filemap_map_pages() is calling into the page allocator while holding rcu_read_lock (sleeping is not allowed inside RCU read-side critical sections). According to Kirill Shutemov, the prefaulting code in do_fault_around() is supposed to take care of this, but missing error handling means that the allocation failure can go unnoticed. We don't need to return VM_FAULT_OOM (or any other error) here, since we can just let the normal fault path try again. Fixes: 7267ec008b5c ("mm: postpone page table allocation until we have page to map") Link: http://lkml.kernel.org/r/1469708107-11868-1-git-send-email-vegard.nossum@oracle.com Signed-off-by: Vegard Nossum Acked-by: Kirill A. Shutemov Cc: "Hillf Danton" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'mm/memory.c') diff --git a/mm/memory.c b/mm/memory.c index 4425b6059339..04004834e985 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3133,6 +3133,8 @@ static int do_fault_around(struct fault_env *fe, pgoff_t start_pgoff) if (pmd_none(*fe->pmd)) { fe->prealloc_pte = pte_alloc_one(fe->vma->vm_mm, fe->address); + if (!fe->prealloc_pte) + goto out; smp_wmb(); /* See comment in __pte_alloc() */ } -- cgit v1.2.3-59-g8ed1b