From: "Matthew Wilcox (Oracle)" <willy@infradead.org> mainline inclusion from mainline-v6.10-rc1 commit 3be51060599ff01899b6d8c3f8aca456506cf5ea category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9R3AY CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Patch series "Improve anon_vma scalability for anon VMAs". We have a 3x throughput improvement reported by Intel's kernel test robot: https://lore.kernel.org/all/202404261055.c5e24608-oliver.sang@intel.com/ This is from delaying taking the mmap_lock for page faults until we actually need the mmap_lock in order to assign an anon_vma to the vma. It cleans up the page fault path a little by making the anon fault handler more similar to the file fault handler. This patch (of 4): Convert the comment into an assertion. Link: https://lkml.kernel.org/r/20240426144506.1290619-1-willy@infradead.org Link: https://lkml.kernel.org/r/20240426144506.1290619-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Liu Shixin <liushixin2@huawei.com> --- mm/rmap.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 88345e743c4f..27f8881be2ad 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -182,8 +182,6 @@ static void anon_vma_chain_link(struct vm_area_struct *vma, * for the new allocation. At the same time, we do not want * to do any locking for the common case of already having * an anon_vma. - * - * This must be called with the mmap_lock held for reading. */ int __anon_vma_prepare(struct vm_area_struct *vma) { @@ -191,6 +189,7 @@ int __anon_vma_prepare(struct vm_area_struct *vma) struct anon_vma *anon_vma, *allocated; struct anon_vma_chain *avc; + mmap_assert_locked(mm); might_sleep(); avc = anon_vma_chain_alloc(GFP_KERNEL); -- 2.25.1