From f5617ffeb450f84c57f7eba1a3524a29955d42b7 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Mon, 24 Jul 2023 19:54:08 +0100 Subject: [PATCH] mm: run the fault-around code under the VMA lock The map_pages fs method should be safe to run under the VMA lock instead of the mmap lock. This should have a measurable reduction in contention on the mmap lock. Link: https://lkml.kernel.org/r/20230724185410.1124082-9-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Suren Baghdasaryan Cc: Arjun Roy Cc: Eric Dumazet Cc: Punit Agrawal Signed-off-by: Andrew Morton --- mm/memory.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 23a20b7..52235aa 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4533,11 +4533,6 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf) vm_fault_t ret = 0; struct folio *folio; - if (vmf->flags & FAULT_FLAG_VMA_LOCK) { - vma_end_read(vmf->vma); - return VM_FAULT_RETRY; - } - /* * Let's call ->map_pages() first and use ->fault() as fallback * if page by the offset is not ready to be mapped (cold cache or @@ -4549,6 +4544,11 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf) return ret; } + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + vma_end_read(vmf->vma); + return VM_FAULT_RETRY; + } + ret = __do_fault(vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; -- 2.7.4