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mm: optimise vmf_anon_prepare() for VMAs without an anon_vma

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If the mmap_lock can be taken for read, we can call __anon_vma_prepare()
while holding it, saving ourselves a trip back through the fault handler.

Link: https://lkml.kernel.org/r/20240426144506.1290619-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jann Horn <jannh@google.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-04-26 15:45:03 +01:00 committed by Andrew Morton
parent 73b4a0cd82
commit 737019cf6a
1 changed files with 9 additions and 4 deletions
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13
mm/memory.c
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@ -3232,16 +3232,21 @@ static inline vm_fault_t vmf_can_call_fault(const struct vm_fault *vmf)
vm_fault_t vmf_anon_prepare(struct vm_fault *vmf) vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
{ {
struct vm_area_struct *vma = vmf->vma; struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret = 0;
if (likely(vma->anon_vma)) if (likely(vma->anon_vma))
return 0; return 0;
if (vmf->flags & FAULT_FLAG_VMA_LOCK) { if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
vma_end_read(vma); if (!mmap_read_trylock(vma->vm_mm)) {
return VM_FAULT_RETRY; vma_end_read(vma);
return VM_FAULT_RETRY;
}
} }
if (__anon_vma_prepare(vma)) if (__anon_vma_prepare(vma))
return VM_FAULT_OOM; ret = VM_FAULT_OOM;
return 0; if (vmf->flags & FAULT_FLAG_VMA_LOCK)
mmap_read_unlock(vma->vm_mm);
return ret;
} }
/* /*