From 0d2ebf9c3f7822e7ba3e4792ea3b6b19aa2da34a Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Mon, 27 Feb 2023 09:36:31 -0800 Subject: mm/mmap: free vm_area_struct without call_rcu in exit_mmap call_rcu() can take a long time when callback offloading is enabled. Its use in the vm_area_free can cause regressions in the exit path when multiple VMAs are being freed. Because exit_mmap() is called only after the last mm user drops its refcount, the page fault handlers can't be racing with it. Any other possible user like oom-reaper or process_mrelease are already synchronized using mmap_lock. Therefore exit_mmap() can free VMAs directly, without the use of call_rcu(). Expose __vm_area_free() and use it from exit_mmap() to avoid possible call_rcu() floods and performance regressions caused by it. Link: https://lkml.kernel.org/r/20230227173632.3292573-33-surenb@google.com Signed-off-by: Suren Baghdasaryan Signed-off-by: Andrew Morton --- mm/mmap.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'mm/mmap.c') diff --git a/mm/mmap.c b/mm/mmap.c index b42f58591b9a..511f656eb423 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -133,7 +133,7 @@ void unlink_file_vma(struct vm_area_struct *vma) /* * Close a vm structure and free it. */ -static void remove_vma(struct vm_area_struct *vma) +static void remove_vma(struct vm_area_struct *vma, bool unreachable) { might_sleep(); if (vma->vm_ops && vma->vm_ops->close) @@ -141,7 +141,10 @@ static void remove_vma(struct vm_area_struct *vma) if (vma->vm_file) fput(vma->vm_file); mpol_put(vma_policy(vma)); - vm_area_free(vma); + if (unreachable) + __vm_area_free(vma); + else + vm_area_free(vma); } static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi, @@ -2145,7 +2148,7 @@ static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas) if (vma->vm_flags & VM_ACCOUNT) nr_accounted += nrpages; vm_stat_account(mm, vma->vm_flags, -nrpages); - remove_vma(vma); + remove_vma(vma, false); } vm_unacct_memory(nr_accounted); validate_mm(mm); @@ -3078,7 +3081,7 @@ void exit_mmap(struct mm_struct *mm) do { if (vma->vm_flags & VM_ACCOUNT) nr_accounted += vma_pages(vma); - remove_vma(vma); + remove_vma(vma, true); count++; cond_resched(); } while ((vma = mas_find(&mas, ULONG_MAX)) != NULL); -- cgit