| Date | Thu, 19 Jan 2023 17:37:31 -0500 | From | Peter Xu <> | Subject | Re: [PATCH 35/46] hugetlb: add MADV_COLLAPSE for hugetlb |
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On Thu, Jan 05, 2023 at 10:18:33AM +0000, James Houghton wrote: > + /* > + * Grab the VMA lock and mapping sem for writing. This will prevent > + * concurrent high-granularity page table walks, so that we can safely > + * collapse and free page tables. > + * > + * This is the same locking that huge_pmd_unshare requires. > + */ > + hugetlb_vma_lock_write(vma); > + i_mmap_lock_write(vma->vm_file->f_mapping);
One thing I just noticed - do we need the mmap write lock here? I don't quickly see what stops another thread from having the mmap read and walking upon the pgtables being collapsed.
Thanks,
-- Peter Xu
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