From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 915486B0003 for ; Fri, 8 Jun 2018 14:58:18 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id x22-v6so1378187wmc.7 for ; Fri, 08 Jun 2018 11:58:18 -0700 (PDT) Received: from mx0a-00190b01.pphosted.com (mx0a-00190b01.pphosted.com. [2620:100:9001:583::1]) by mx.google.com with ESMTPS id 19-v6si620153edz.385.2018.06.08.11.58.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Jun 2018 11:58:16 -0700 (PDT) From: Jason Baron Subject: [PATCH] mm/madvise: allow MADV_DONTNEED to free memory that is MLOCK_ONFAULT Date: Fri, 8 Jun 2018 14:56:52 -0400 Message-Id: <1528484212-7199-1-git-send-email-jbaron@akamai.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Michal Hocko , Vlastimil Babka , Joonsoo Kim , Mel Gorman , "Kirill A. Shutemov" In order to free memory that is marked MLOCK_ONFAULT, the memory region needs to be first unlocked, before calling MADV_DONTNEED. And if the region is to be reused as MLOCK_ONFAULT, we require another call to mlock2() with the MLOCK_ONFAULT flag. Let's simplify freeing memory that is set MLOCK_ONFAULT, by allowing MADV_DONTNEED to work directly for memory that is set MLOCK_ONFAULT. The locked memory limits, tracked by mm->locked_vm do not need to be adjusted in this case, since they were charged to the entire region when MLOCK_ONFAULT was initially set. Further, I don't think allowing MADV_FREE for MLOCK_ONFAULT regions makes sense, since the point of MLOCK_ONFAULT is for userspace to know when pages are locked in memory and thus to know when page faults will occur. Signed-off-by: Jason Baron Cc: Andrew Morton Cc: Michal Hocko Cc: Vlastimil Babka Cc: Joonsoo Kim Cc: Mel Gorman Cc: Kirill A. Shutemov --- mm/internal.h | 18 ++++++++++++++++++ mm/madvise.c | 4 ++-- mm/oom_kill.c | 2 +- 3 files changed, 21 insertions(+), 3 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 9e3654d..16c0041 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -15,6 +15,7 @@ #include #include #include +#include /* * The set of flags that only affect watermark checking and reclaim @@ -45,9 +46,26 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma, static inline bool can_madv_dontneed_vma(struct vm_area_struct *vma) { + return !(((vma->vm_flags & (VM_LOCKED|VM_LOCKONFAULT)) == VM_LOCKED) || + (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))); +} + +static inline bool can_madv_free_vma(struct vm_area_struct *vma) +{ return !(vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP)); } +static inline bool can_madv_dontneed_or_free_vma(struct vm_area_struct *vma, + int behavior) +{ + if (behavior == MADV_DONTNEED) + return can_madv_dontneed_vma(vma); + else if (behavior == MADV_FREE) + return can_madv_free_vma(vma); + else + return 0; +} + void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long addr, unsigned long end, diff --git a/mm/madvise.c b/mm/madvise.c index 4d3c922..61ff306 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -517,7 +517,7 @@ static long madvise_dontneed_free(struct vm_area_struct *vma, int behavior) { *prev = vma; - if (!can_madv_dontneed_vma(vma)) + if (!can_madv_dontneed_or_free_vma(vma, behavior)) return -EINVAL; if (!userfaultfd_remove(vma, start, end)) { @@ -539,7 +539,7 @@ static long madvise_dontneed_free(struct vm_area_struct *vma, */ return -ENOMEM; } - if (!can_madv_dontneed_vma(vma)) + if (!can_madv_dontneed_or_free_vma(vma, behavior)) return -EINVAL; if (end > vma->vm_end) { /* diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 8ba6cb8..9817d15 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -492,7 +492,7 @@ void __oom_reap_task_mm(struct mm_struct *mm) set_bit(MMF_UNSTABLE, &mm->flags); for (vma = mm->mmap ; vma; vma = vma->vm_next) { - if (!can_madv_dontneed_vma(vma)) + if (!can_madv_free_vma(vma)) continue; /* -- 2.7.4