From: Brian Geffon <bgeffon@google.com> mainline inclusion from mainline-v6.14-rc6 commit 34b82f33cf3f03bc39e9a205a913d790e1520ade category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBRQ5C Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- When handling faults for anon shmem finish_fault() will attempt to install ptes for the entire folio. Unfortunately if it encounters a single non-pte_none entry in that range it will bail, even if the pte that triggered the fault is still pte_none. When this situation happens the fault will be retried endlessly never making forward progress. This patch fixes this behavior and if it detects that a pte in the range is not pte_none it will fall back to setting a single pte. [bgeffon@google.com: tweak whitespace] Link: https://lkml.kernel.org/r/20250227133236.1296853-1-bgeffon@google.com Link: https://lkml.kernel.org/r/20250226162341.915535-1-bgeffon@google.com Fixes: 43e027e41423 ("mm: memory: extend finish_fault() to support large folio") Signed-off-by: Brian Geffon <bgeffon@google.com> Suggested-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reported-by: Marek Maslanka <mmaslanka@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickens <hughd@google.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Zi Yan <ziy@nvidia.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> --- mm/memory.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index a6d146d684e8..e8daa5a3d369 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4846,7 +4846,11 @@ vm_fault_t finish_fault(struct vm_fault *vmf) bool is_cow = (vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED); int type, nr_pages; - unsigned long addr = vmf->address; + unsigned long addr; + bool needs_fallback = false; + +fallback: + addr = vmf->address; /* Did we COW the page? */ if (is_cow) @@ -4885,7 +4889,8 @@ vm_fault_t finish_fault(struct vm_fault *vmf) * approach also applies to non-anonymous-shmem faults to avoid * inflating the RSS of the process. */ - if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) { + if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma)) || + unlikely(needs_fallback)) { nr_pages = 1; } else if (nr_pages > 1) { pgoff_t idx = folio_page_idx(folio, page); @@ -4921,9 +4926,9 @@ vm_fault_t finish_fault(struct vm_fault *vmf) ret = VM_FAULT_NOPAGE; goto unlock; } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) { - update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages); - ret = VM_FAULT_NOPAGE; - goto unlock; + needs_fallback = true; + pte_unmap_unlock(vmf->pte, vmf->ptl); + goto fallback; } folio_ref_add(folio, nr_pages - 1); -- 2.25.1