Commit f5617ffe authored Jul 24, 2023 by Matthew Wilcox (Oracle) Committed by Andrew Morton Aug 18, 2023

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) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 61a4b8d3

mm/memory.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -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;