Re: [RFC v8 PATCH 3/5] mm: mmap: zap pages with read mmap_sem in munmap

From: Yang Shi
Date: Wed Aug 22 2018 - 15:20:54 EST




On 8/22/18 4:11 AM, Vlastimil Babka wrote:
On 08/15/2018 08:49 PM, Yang Shi wrote:

+ start_vma = munmap_lookup_vma(mm, start, end);
+ if (!start_vma)
+ goto out;
+ if (IS_ERR(start_vma)) {
+ ret = PTR_ERR(start_vma);
+ goto out;
+ }
+
+ prev = start_vma->vm_prev;
+
+ if (unlikely(uf)) {
+ ret = userfaultfd_unmap_prep(start_vma, start, end, uf);
+ if (ret)
+ goto out;
+ }
+
You sure it's ok to redo this in case of goto regular path? The
preparations have some side-effects... I would rather move this after
the regular path check?

This preparation sets vma->vm_userfaultfd_ctx.ctx for each vmas. But, before doing this, it calls has_unmap_ctx() to check if the ctx has been set or not. If it has been set, it just skip the vma. It sounds ok, right?