From 6283acb6b78343a9f819fccf6748c80e3ecc488c Mon Sep 17 00:00:00 2001 From: Andreas Kling Date: Mon, 9 Aug 2021 01:27:30 +0200 Subject: [PATCH] Kernel/SMP: Don't panic in inode fault if other CPU already paged it in It may happen that CPU A manages to page in from the same inode while we're just entering the same page fault handler on CPU B. Handle it gracefully by checking if the data has already been paged in (instead of VERIFY'ing that it hasn't) and then remap the page if that's the case. --- Kernel/Memory/Region.cpp | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/Kernel/Memory/Region.cpp b/Kernel/Memory/Region.cpp index 3318fa5c029..648b20ba8aa 100644 --- a/Kernel/Memory/Region.cpp +++ b/Kernel/Memory/Region.cpp @@ -401,7 +401,16 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region) auto page_index_in_vmobject = translate_to_vmobject_page(page_index_in_region); auto& vmobject_physical_page_entry = inode_vmobject.physical_pages()[page_index_in_vmobject]; - VERIFY(vmobject_physical_page_entry.is_null()); + + { + ScopedSpinLock locker(inode_vmobject.m_lock); + if (!vmobject_physical_page_entry.is_null()) { + dbgln_if(PAGE_FAULT_DEBUG, "handle_inode_fault: Page faulted in by someone else before reading, remapping."); + if (!remap_vmobject_page(page_index_in_vmobject)) + return PageFaultResponse::OutOfMemory; + return PageFaultResponse::Continue; + } + } dbgln_if(PAGE_FAULT_DEBUG, "Inode fault in {} page index: {}", name(), page_index_in_region);