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d1716b4b78
Allow multiple callers to install pages simultaneously by switching the mmap_sem from write-mode to read-mode. Races to the same PTE are handled using get_user_pages_remote() to retrieve the already installed page. This method significantly reduces contention in the mmap semaphore. To ensure safety, vma_lookup() is used (instead of alloc->vma) to avoid operating on an isolated VMA. In addition, zap_page_range_single() is called under the alloc->mutex to avoid racing with the shrinker. Many thanks to Barry Song who posted a similar approach [1]. Link: https://lore.kernel.org/all/20240902225009.34576-1-21cnbao@gmail.com/ [1] Cc: David Hildenbrand <david@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Liam R. Howlett <Liam.Howlett@oracle.com> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20241210143114.661252-3-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>