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From: Suren Baghdasaryan <surenb@google.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	 linux-mm <linux-mm@kvack.org>,
	linux-api@vger.kernel.org, oleksandr@redhat.com,
	 Tim Murray <timmurray@google.com>,
	Daniel Colascione <dancol@google.com>,
	 Sandeep Patil <sspatil@google.com>,
	Sonny Rao <sonnyrao@google.com>,
	 Brian Geffon <bgeffon@google.com>,
	Michal Hocko <mhocko@suse.com>,
	 Johannes Weiner <hannes@cmpxchg.org>,
	Shakeel Butt <shakeelb@google.com>,
	 John Dias <joaodias@google.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	sj38.park@gmail.com,  alexander.h.duyck@linux.intel.com,
	Jann Horn <jannh@google.com>,  Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH v6 1/7] mm: pass task and mm to do_madvise
Date: Fri, 28 Feb 2020 14:15:42 -0800	[thread overview]
Message-ID: <CAJuCfpGdOUp4pU2TyC3O=kCwL85wOc5szbNVTy9iSLe-CKVvzA@mail.gmail.com> (raw)
In-Reply-To: <20200219014433.88424-2-minchan@kernel.org>

On Tue, Feb 18, 2020 at 5:44 PM Minchan Kim <minchan@kernel.org> wrote:
>
> In upcoming patches, do_madvise will be called from external process
> context so we shouldn't asssume "current" is always hinted process's
> task_struct. Furthermore, we couldn't access mm_struct via task->mm
> once it's verified by access_mm which will be introduced in next
> patch[1]. And let's pass *current* and current->mm as arguments of
> do_madvise so it shouldn't change existing behavior but prepare
> next patch to make review easy.
>
> Note: io_madvise pass NULL as target_task argument of do_madvise
> because it couldn't know who is target.
>
> [1] http://lore.kernel.org/r/CAG48ez27=pwm5m_N_988xT1huO7g7h6arTQL44zev6TD-h-7Tg@mail.gmail.com
>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Jann Horn <jannh@google.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
>  fs/io_uring.c      |  2 +-
>  include/linux/mm.h |  3 ++-
>  mm/madvise.c       | 34 +++++++++++++++++++---------------
>  3 files changed, 22 insertions(+), 17 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 63beda9bafc5..a858da2ae2f4 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2736,7 +2736,7 @@ static int io_madvise(struct io_kiocb *req, struct io_kiocb **nxt,
>         if (force_nonblock)
>                 return -EAGAIN;
>
> -       ret = do_madvise(ma->addr, ma->len, ma->advice);
> +       ret = do_madvise(NULL, req->work.mm, ma->addr, ma->len, ma->advice);
>         if (ret < 0)
>                 req_set_fail_links(req);
>         io_cqring_add_event(req, ret);
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 52269e56c514..bc16c8774328 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2323,7 +2323,8 @@ extern int __do_munmap(struct mm_struct *, unsigned long, size_t,
>                        struct list_head *uf, bool downgrade);
>  extern int do_munmap(struct mm_struct *, unsigned long, size_t,
>                      struct list_head *uf);
> -extern int do_madvise(unsigned long start, size_t len_in, int behavior);
> +extern int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
> +               unsigned long start, size_t len_in, int behavior);
>
>  static inline unsigned long
>  do_mmap_pgoff(struct file *file, unsigned long addr,
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 43b47d3fae02..f75c86b6c463 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -254,6 +254,7 @@ static long madvise_willneed(struct vm_area_struct *vma,
>                              struct vm_area_struct **prev,
>                              unsigned long start, unsigned long end)
>  {
> +       struct mm_struct *mm = vma->vm_mm;
>         struct file *file = vma->vm_file;
>         loff_t offset;
>
> @@ -288,12 +289,12 @@ static long madvise_willneed(struct vm_area_struct *vma,
>          */
>         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
>         get_file(file);
> -       up_read(&current->mm->mmap_sem);
> +       up_read(&mm->mmap_sem);
>         offset = (loff_t)(start - vma->vm_start)
>                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
>         vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
>         fput(file);
> -       down_read(&current->mm->mmap_sem);
> +       down_read(&mm->mmap_sem);
>         return 0;
>  }
>
> @@ -676,7 +677,6 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
>         if (nr_swap) {
>                 if (current->mm == mm)
>                         sync_mm_rss(mm);
> -
>                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
>         }
>         arch_leave_lazy_mmu_mode();
> @@ -756,6 +756,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
>                                   unsigned long start, unsigned long end,
>                                   int behavior)
>  {
> +       struct mm_struct *mm = vma->vm_mm;
> +
>         *prev = vma;
>         if (!can_madv_lru_vma(vma))
>                 return -EINVAL;
> @@ -763,8 +765,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
>         if (!userfaultfd_remove(vma, start, end)) {
>                 *prev = NULL; /* mmap_sem has been dropped, prev is stale */
>
> -               down_read(&current->mm->mmap_sem);
> -               vma = find_vma(current->mm, start);
> +               down_read(&mm->mmap_sem);
> +               vma = find_vma(mm, start);
>                 if (!vma)
>                         return -ENOMEM;
>                 if (start < vma->vm_start) {
> @@ -818,6 +820,7 @@ static long madvise_remove(struct vm_area_struct *vma,
>         loff_t offset;
>         int error;
>         struct file *f;
> +       struct mm_struct *mm = vma->vm_mm;
>
>         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
>
> @@ -845,13 +848,13 @@ static long madvise_remove(struct vm_area_struct *vma,
>         get_file(f);
>         if (userfaultfd_remove(vma, start, end)) {
>                 /* mmap_sem was not released by userfaultfd_remove() */
> -               up_read(&current->mm->mmap_sem);
> +               up_read(&mm->mmap_sem);
>         }
>         error = vfs_fallocate(f,
>                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
>                                 offset, end - start);
>         fput(f);
> -       down_read(&current->mm->mmap_sem);
> +       down_read(&mm->mmap_sem);
>         return error;
>  }
>
> @@ -1044,7 +1047,8 @@ madvise_behavior_valid(int behavior)
>   *  -EBADF  - map exists, but area maps something that isn't a file.
>   *  -EAGAIN - a kernel resource was temporarily unavailable.
>   */
> -int do_madvise(unsigned long start, size_t len_in, int behavior)
> +int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
> +               unsigned long start, size_t len_in, int behavior)
>  {
>         unsigned long end, tmp;
>         struct vm_area_struct *vma, *prev;
> @@ -1082,10 +1086,10 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)
>
>         write = madvise_need_mmap_write(behavior);
>         if (write) {
> -               if (down_write_killable(&current->mm->mmap_sem))
> +               if (down_write_killable(&mm->mmap_sem))
>                         return -EINTR;
>         } else {
> -               down_read(&current->mm->mmap_sem);
> +               down_read(&mm->mmap_sem);
>         }
>
>         /*
> @@ -1093,7 +1097,7 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)
>          * ranges, just ignore them, but return -ENOMEM at the end.
>          * - different from the way of handling in mlock etc.
>          */
> -       vma = find_vma_prev(current->mm, start, &prev);
> +       vma = find_vma_prev(mm, start, &prev);
>         if (vma && start > vma->vm_start)
>                 prev = vma;
>
> @@ -1130,19 +1134,19 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)
>                 if (prev)
>                         vma = prev->vm_next;
>                 else    /* madvise_remove dropped mmap_sem */
> -                       vma = find_vma(current->mm, start);
> +                       vma = find_vma(mm, start);
>         }
>  out:
>         blk_finish_plug(&plug);
>         if (write)
> -               up_write(&current->mm->mmap_sem);
> +               up_write(&mm->mmap_sem);
>         else
> -               up_read(&current->mm->mmap_sem);
> +               up_read(&mm->mmap_sem);
>
>         return error;
>  }
>
>  SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
>  {
> -       return do_madvise(start, len_in, behavior);
> +       return do_madvise(current, current->mm, start, len_in, behavior);
>  }
> --
> 2.25.0.265.gbab2e86ba0-goog
>

Reviewed-by: Suren Baghdasaryan <surenb@google.com>


  reply	other threads:[~2020-02-28 22:15 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-19  1:44 [PATCH v6 0/7] introduce memory hinting API for external process Minchan Kim
2020-02-19  1:44 ` [PATCH v6 1/7] mm: pass task and mm to do_madvise Minchan Kim
2020-02-28 22:15   ` Suren Baghdasaryan [this message]
2020-02-19  1:44 ` [PATCH v6 2/7] mm: introduce external memory hinting API Minchan Kim
2020-02-20 19:13   ` kbuild test robot
2020-02-20 21:15     ` Minchan Kim
2020-02-20 21:21       ` Minchan Kim
2020-02-28 22:14         ` Suren Baghdasaryan
2020-03-02 19:18           ` Minchan Kim
2020-02-20 20:48   ` kbuild test robot
2020-02-19  1:44 ` [PATCH v6 3/7] mm: check fatal signal pending of target process Minchan Kim
2020-02-28 22:20   ` Suren Baghdasaryan
2020-02-19  1:44 ` [PATCH v6 4/7] pid: move pidfd_get_pid function to pid.c Minchan Kim
2020-02-28 22:22   ` Suren Baghdasaryan
2020-02-19  1:44 ` [PATCH v6 5/7] mm: support both pid and pidfd for process_madvise Minchan Kim
2020-02-28 22:41   ` Suren Baghdasaryan
2020-03-02 19:23     ` Minchan Kim
2020-03-02 19:38       ` Suren Baghdasaryan
2020-02-19  1:44 ` [PATCH v6 6/7] mm/madvise: employ mmget_still_valid for write lock Minchan Kim
2020-02-28 23:19   ` Suren Baghdasaryan
2020-03-02  7:33     ` Oleksandr Natalenko
2020-03-02 16:32       ` Suren Baghdasaryan
2020-02-19  1:44 ` [PATCH v6 7/7] mm/madvise: allow KSM hints for remote API Minchan Kim
2020-02-19 20:01 ` [PATCH v6 0/7] introduce memory hinting API for external process Andrew Morton
2020-02-19 21:05   ` Suren Baghdasaryan
2020-02-19 22:32   ` Minchan Kim
2020-02-19 22:51     ` Brian Geffon
2020-02-20  9:16   ` SeongJae Park

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