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Message-ID: <Y7wsE3wiD2FBJoaz@vernon-pc>
Date: Mon, 9 Jan 2023 23:10:00 +0800
From: Vernon Yang <vernon2gm@...il.com>
To: Liam Howlett <liam.howlett@...cle.com>
Cc: "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 06/44] mm/mmap: convert brk to use vma iterator
Hello Liam,
On Thu, Jan 05, 2023 at 07:15:54PM +0000, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>
> Use the vma iterator API for the brk() system call. This will provide
> type safety at compile time.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
> mm/mmap.c | 47 +++++++++++++++++++++++------------------------
> 1 file changed, 23 insertions(+), 24 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 9318f2ac8a6e..4a6f42ab3560 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -239,10 +239,10 @@ static int check_brk_limits(unsigned long addr, unsigned long len)
>
> return mlock_future_check(current->mm, current->mm->def_flags, len);
> }
> -static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
> +static int do_brk_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> unsigned long newbrk, unsigned long oldbrk,
> struct list_head *uf);
> -static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *brkvma,
> +static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *brkvma,
> unsigned long addr, unsigned long request, unsigned long flags);
> SYSCALL_DEFINE1(brk, unsigned long, brk)
> {
> @@ -253,7 +253,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
> bool populate;
> bool downgraded = false;
> LIST_HEAD(uf);
> - MA_STATE(mas, &mm->mm_mt, 0, 0);
> + struct vma_iterator vmi;
>
> if (mmap_write_lock_killable(mm))
> return -EINTR;
> @@ -301,8 +301,8 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
> int ret;
>
> /* Search one past newbrk */
> - mas_set(&mas, newbrk);
> - brkvma = mas_find(&mas, oldbrk);
> + vma_iter_init(&vmi, mm, newbrk);
> + brkvma = vma_find(&vmi, oldbrk);
> if (!brkvma || brkvma->vm_start >= oldbrk)
> goto out; /* mapping intersects with an existing non-brk vma. */
> /*
> @@ -311,7 +311,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
> * before calling do_brk_munmap().
> */
> mm->brk = brk;
> - ret = do_brk_munmap(&mas, brkvma, newbrk, oldbrk, &uf);
> + ret = do_brk_munmap(&vmi, brkvma, newbrk, oldbrk, &uf);
> if (ret == 1) {
> downgraded = true;
> goto success;
> @@ -329,14 +329,14 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
> * Only check if the next VMA is within the stack_guard_gap of the
> * expansion area
> */
> - mas_set(&mas, oldbrk);
> - next = mas_find(&mas, newbrk - 1 + PAGE_SIZE + stack_guard_gap);
> + vma_iter_init(&vmi, mm, oldbrk);
> + next = vma_find(&vmi, newbrk + PAGE_SIZE + stack_guard_gap);
> if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
> goto out;
>
> - brkvma = mas_prev(&mas, mm->start_brk);
> + brkvma = vma_prev_limit(&vmi, mm->start_brk);
> /* Ok, looks good - let it rip. */
> - if (do_brk_flags(&mas, brkvma, oldbrk, newbrk - oldbrk, 0) < 0)
> + if (do_brk_flags(&vmi, brkvma, oldbrk, newbrk - oldbrk, 0) < 0)
> goto out;
>
> mm->brk = brk;
> @@ -2963,7 +2963,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>
> /*
> * brk_munmap() - Unmap a parital vma.
> - * @mas: The maple tree state.
> + * @vmi: The vma iterator
> * @vma: The vma to be modified
> * @newbrk: the start of the address to unmap
> * @oldbrk: The end of the address to unmap
> @@ -2973,7 +2973,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
> * unmaps a partial VMA mapping. Does not handle alignment, downgrades lock if
> * possible.
> */
> -static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
> +static int do_brk_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> unsigned long newbrk, unsigned long oldbrk,
> struct list_head *uf)
> {
> @@ -2981,14 +2981,14 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
> int ret;
>
> arch_unmap(mm, newbrk, oldbrk);
> - ret = do_mas_align_munmap(mas, vma, mm, newbrk, oldbrk, uf, true);
> + ret = do_mas_align_munmap(&vmi->mas, vma, mm, newbrk, oldbrk, uf, true);
> validate_mm_mt(mm);
> return ret;
> }
>
> /*
> * do_brk_flags() - Increase the brk vma if the flags match.
> - * @mas: The maple tree state.
> + * @vmi: The vma iterator
> * @addr: The start address
> * @len: The length of the increase
> * @vma: The vma,
> @@ -2998,7 +2998,7 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
> * do not match then create a new anonymous VMA. Eventually we may be able to
> * do some brk-specific accounting here.
> */
> -static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
> +static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
> unsigned long addr, unsigned long len, unsigned long flags)
> {
> struct mm_struct *mm = current->mm;
> @@ -3025,8 +3025,7 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
> if (vma && vma->vm_end == addr && !vma_policy(vma) &&
> can_vma_merge_after(vma, flags, NULL, NULL,
> addr >> PAGE_SHIFT, NULL_VM_UFFD_CTX, NULL)) {
> - mas_set_range(mas, vma->vm_start, addr + len - 1);
Why was mas_set_range() removed here, but below [1] it’s left?
> - if (mas_preallocate(mas, vma, GFP_KERNEL))
> + if (vma_iter_prealloc(vmi, vma))
> goto unacct_fail;
>
> vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
> @@ -3036,7 +3035,7 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
> }
> vma->vm_end = addr + len;
> vma->vm_flags |= VM_SOFTDIRTY;
> - mas_store_prealloc(mas, vma);
> + vma_iter_store(vmi, vma);
>
> if (vma->anon_vma) {
> anon_vma_interval_tree_post_update_vma(vma);
> @@ -3057,8 +3056,8 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
> vma->vm_pgoff = addr >> PAGE_SHIFT;
> vma->vm_flags = flags;
> vma->vm_page_prot = vm_get_page_prot(flags);
> - mas_set_range(mas, vma->vm_start, addr + len - 1);
> - if (mas_store_gfp(mas, vma, GFP_KERNEL))
> + mas_set_range(&vmi->mas, vma->vm_start, vma->vm_end - 1);
[1]. the mas_set_range() here has been reserved.
> + if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL))
> goto mas_store_fail;
>
> mm->map_count++;
> @@ -3087,7 +3086,7 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
> int ret;
> bool populate;
> LIST_HEAD(uf);
> - MA_STATE(mas, &mm->mm_mt, addr, addr);
> + VMA_ITERATOR(vmi, mm, addr);
>
> len = PAGE_ALIGN(request);
> if (len < request)
> @@ -3106,12 +3105,12 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
> if (ret)
> goto limits_failed;
>
> - ret = do_mas_munmap(&mas, mm, addr, len, &uf, 0);
> + ret = do_mas_munmap(&vmi.mas, mm, addr, len, &uf, 0);
> if (ret)
> goto munmap_failed;
>
> - vma = mas_prev(&mas, 0);
> - ret = do_brk_flags(&mas, vma, addr, len, flags);
> + vma = vma_prev(&vmi);
> + ret = do_brk_flags(&vmi, vma, addr, len, flags);
> populate = ((mm->def_flags & VM_LOCKED) != 0);
> mmap_write_unlock(mm);
> userfaultfd_unmap_complete(mm, &uf);
> --
> 2.35.1
>
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