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Message-ID: <bf24fc3c-a092-4c37-8f2f-ae32cbafe036@lucifer.local>
Date: Fri, 5 Jul 2024 19:01:02 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>,
sidhartha.kumar@...cle.com, "Paul E . McKenney" <paulmck@...nel.org>,
Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 04/16] mm/mmap: Extract the gathering of vmas from
do_vmi_align_munmap()
On Thu, Jul 04, 2024 at 02:27:06PM GMT, Liam R. Howlett wrote:
> Create vmi_gather_munmap_vmas() to handle the gathering of vmas into a
> detached maple tree for removal later. Part of the gathering is the
> splitting of vmas that span the boundary.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
> mm/mmap.c | 82 +++++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 58 insertions(+), 24 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 411798f46932..8dc8ffbf9d8d 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2656,32 +2656,29 @@ vmi_complete_munmap_vmas(struct vma_iterator *vmi, struct vm_area_struct *vma,
> }
>
> /*
> - * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
> + * vmi_gather_munmap_vmas() - Put all VMAs within a range into a maple tree
> + * for removal at a later date. Handles splitting first and last if necessary
> + * and marking the vmas as isolated.
> + *
> * @vmi: The vma iterator
> * @vma: The starting vm_area_struct
> * @mm: The mm_struct
> * @start: The aligned start address to munmap.
> * @end: The aligned end address to munmap.
> * @uf: The userfaultfd list_head
> - * @unlock: Set to true to drop the mmap_lock. unlocking only happens on
> - * success.
> + * @mas_detach: The maple state tracking the detached tree
Missing the locked_vm parameter.
> *
> - * Return: 0 on success and drops the lock if so directed, error and leaves the
> - * lock held otherwise.
> + * Return: 0 on success
> */
> static int
> -do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> +vmi_gather_munmap_vmas(struct vma_iterator *vmi, struct vm_area_struct *vma,
> struct mm_struct *mm, unsigned long start,
> - unsigned long end, struct list_head *uf, bool unlock)
> + unsigned long end, struct list_head *uf,
> + struct ma_state *mas_detach, unsigned long *locked_vm)
> {
> struct vm_area_struct *next = NULL;
> - struct maple_tree mt_detach;
> int count = 0;
> int error = -ENOMEM;
> - unsigned long locked_vm = 0;
> - MA_STATE(mas_detach, &mt_detach, 0, 0);
> - mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
> - mt_on_stack(mt_detach);
>
> /*
> * If we need to split any vma, do it now to save pain later.
> @@ -2720,15 +2717,14 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> goto end_split_failed;
> }
> vma_start_write(next);
> - mas_set(&mas_detach, count);
> - error = mas_store_gfp(&mas_detach, next, GFP_KERNEL);
> + mas_set(mas_detach, count++);
> + if (next->vm_flags & VM_LOCKED)
> + *locked_vm += vma_pages(next);
> +
> + error = mas_store_gfp(mas_detach, next, GFP_KERNEL);
> if (error)
> goto munmap_gather_failed;
> vma_mark_detached(next, true);
> - if (next->vm_flags & VM_LOCKED)
> - locked_vm += vma_pages(next);
> -
> - count++;
> if (unlikely(uf)) {
> /*
> * If userfaultfd_unmap_prep returns an error the vmas
> @@ -2753,7 +2749,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> #if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
> /* Make sure no VMAs are about to be lost. */
> {
> - MA_STATE(test, &mt_detach, 0, 0);
> + MA_STATE(test, mas_detach->tree, 0, 0);
> struct vm_area_struct *vma_mas, *vma_test;
> int test_count = 0;
>
> @@ -2773,6 +2769,48 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> while (vma_iter_addr(vmi) > start)
> vma_iter_prev_range(vmi);
>
> + return 0;
> +
> +userfaultfd_error:
> +munmap_gather_failed:
> +end_split_failed:
> + abort_munmap_vmas(mas_detach);
> +start_split_failed:
> +map_count_exceeded:
> + return error;
> +}
> +
> +/*
> + * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
> + * @vmi: The vma iterator
> + * @vma: The starting vm_area_struct
> + * @mm: The mm_struct
> + * @start: The aligned start address to munmap.
> + * @end: The aligned end address to munmap.
> + * @uf: The userfaultfd list_head
> + * @unlock: Set to true to drop the mmap_lock. unlocking only happens on
> + * success.
> + *
> + * Return: 0 on success and drops the lock if so directed, error and leaves the
> + * lock held otherwise.
> + */
> +static int
> +do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> + struct mm_struct *mm, unsigned long start,
> + unsigned long end, struct list_head *uf, bool unlock)
> +{
> + struct maple_tree mt_detach;
> + MA_STATE(mas_detach, &mt_detach, 0, 0);
> + mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
> + mt_on_stack(mt_detach);
> + int error;
> + unsigned long locked_vm = 0;
> +
> + error = vmi_gather_munmap_vmas(vmi, vma, mm, start, end, uf,
> + &mas_detach, &locked_vm);
> + if (error)
> + goto gather_failed;
> +
> error = vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL);
> if (error)
> goto clear_tree_failed;
> @@ -2783,12 +2821,8 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> return 0;
>
> clear_tree_failed:
> -userfaultfd_error:
> -munmap_gather_failed:
> -end_split_failed:
> abort_munmap_vmas(&mas_detach);
> -start_split_failed:
> -map_count_exceeded:
> +gather_failed:
> validate_mm(mm);
> return error;
> }
> --
> 2.43.0
>
>
Other than trivial comment error, LGTM:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
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