Date:	Tue, 1 Sep 2015 21:49:15 +0800
From:	Chen Gang <xili_gchen_5257@...mail.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	"mhocko@...e.cz" <mhocko@...e.cz>
CC:	Linux Memory <linux-mm@...ck.org>,
	kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/mmap.c: Only call vma_unlock_anon_vm() when failure
 occurs in expand_upwards() and expand_downwards()


Sorry for the incorrect format of the patch. So I put the patch into the
attachment which generated by "git format-patch -M HEAD^". Please help
check, thanks.

Next, I shall try to find another mail address which can be accepted by
both China and our mailing list.

Thanks.

On 9/1/15 04:54, Chen Gang wrote:
> When failure occurs, we need not call khugepaged_enter_vma_merge() or
> validate_mm().
>
> Also simplify do_munmap(): declare 'error' 1 time instead of 2 times in
> sub-blocks.
>
> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
> ---
> mm/mmap.c | 116 +++++++++++++++++++++++++++++++-------------------------------
> 1 file changed, 58 insertions(+), 58 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index df6d5f0..d32199a 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2182,10 +2182,9 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
> if (address < PAGE_ALIGN(address+4))
> address = PAGE_ALIGN(address+4);
> else {
> - vma_unlock_anon_vma(vma);
> - return -ENOMEM;
> + error = -ENOMEM;
> + goto err;
> }
> - error = 0;
>
> /* Somebody else might have raced and expanded it already */
> if (address> vma->vm_end) {
> @@ -2194,38 +2193,39 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
> size = address - vma->vm_start;
> grow = (address - vma->vm_end)>> PAGE_SHIFT;
>
> - error = -ENOMEM;
> - if (vma->vm_pgoff + (size>> PAGE_SHIFT)>= vma->vm_pgoff) {
> - error = acct_stack_growth(vma, size, grow);
> - if (!error) {
> - /*
> - * vma_gap_update() doesn't support concurrent
> - * updates, but we only hold a shared mmap_sem
> - * lock here, so we need to protect against
> - * concurrent vma expansions.
> - * vma_lock_anon_vma() doesn't help here, as
> - * we don't guarantee that all growable vmas
> - * in a mm share the same root anon vma.
> - * So, we reuse mm->page_table_lock to guard
> - * against concurrent vma expansions.
> - */
> - spin_lock(&vma->vm_mm->page_table_lock);
> - anon_vma_interval_tree_pre_update_vma(vma);
> - vma->vm_end = address;
> - anon_vma_interval_tree_post_update_vma(vma);
> - if (vma->vm_next)
> - vma_gap_update(vma->vm_next);
> - else
> - vma->vm_mm->highest_vm_end = address;
> - spin_unlock(&vma->vm_mm->page_table_lock);
> -
> - perf_event_mmap(vma);
> - }
> + if (vma->vm_pgoff + (size>> PAGE_SHIFT) < vma->vm_pgoff) {
> + error = -ENOMEM;
> + goto err;
> }
> + error = acct_stack_growth(vma, size, grow);
> + if (error)
> + goto err;
> + /*
> + * vma_gap_update() doesn't support concurrent updates, but we
> + * only hold a shared mmap_sem lock here, so we need to protect
> + * against concurrent vma expansions. vma_lock_anon_vma()
> + * doesn't help here, as we don't guarantee that all growable
> + * vmas in a mm share the same root anon vma. So, we reuse mm->
> + * page_table_lock to guard against concurrent vma expansions.
> + */
> + spin_lock(&vma->vm_mm->page_table_lock);
> + anon_vma_interval_tree_pre_update_vma(vma);
> + vma->vm_end = address;
> + anon_vma_interval_tree_post_update_vma(vma);
> + if (vma->vm_next)
> + vma_gap_update(vma->vm_next);
> + else
> + vma->vm_mm->highest_vm_end = address;
> + spin_unlock(&vma->vm_mm->page_table_lock);
> +
> + perf_event_mmap(vma);
> }
> vma_unlock_anon_vma(vma);
> khugepaged_enter_vma_merge(vma, vma->vm_flags);
> validate_mm(vma->vm_mm);
> + return 0;
> +err:
> + vma_unlock_anon_vma(vma);
> return error;
> }
> #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
> @@ -2265,36 +2265,37 @@ int expand_downwards(struct vm_area_struct *vma,
> size = vma->vm_end - address;
> grow = (vma->vm_start - address)>> PAGE_SHIFT;
>
> - error = -ENOMEM;
> - if (grow <= vma->vm_pgoff) {
> - error = acct_stack_growth(vma, size, grow);
> - if (!error) {
> - /*
> - * vma_gap_update() doesn't support concurrent
> - * updates, but we only hold a shared mmap_sem
> - * lock here, so we need to protect against
> - * concurrent vma expansions.
> - * vma_lock_anon_vma() doesn't help here, as
> - * we don't guarantee that all growable vmas
> - * in a mm share the same root anon vma.
> - * So, we reuse mm->page_table_lock to guard
> - * against concurrent vma expansions.
> - */
> - spin_lock(&vma->vm_mm->page_table_lock);
> - anon_vma_interval_tree_pre_update_vma(vma);
> - vma->vm_start = address;
> - vma->vm_pgoff -= grow;
> - anon_vma_interval_tree_post_update_vma(vma);
> - vma_gap_update(vma);
> - spin_unlock(&vma->vm_mm->page_table_lock);
> -
> - perf_event_mmap(vma);
> - }
> + if (grow> vma->vm_pgoff) {
> + error = -ENOMEM;
> + goto err;
> }
> + error = acct_stack_growth(vma, size, grow);
> + if (error)
> + goto err;
> + /*
> + * vma_gap_update() doesn't support concurrent updates, but we
> + * only hold a shared mmap_sem lock here, so we need to protect
> + * against concurrent vma expansions. vma_lock_anon_vma()
> + * doesn't help here, as we don't guarantee that all growable
> + * vmas in a mm share the same root anon vma. So, we reuse mm->
> + * page_table_lock to guard against concurrent vma expansions.
> + */
> + spin_lock(&vma->vm_mm->page_table_lock);
> + anon_vma_interval_tree_pre_update_vma(vma);
> + vma->vm_start = address;
> + vma->vm_pgoff -= grow;
> + anon_vma_interval_tree_post_update_vma(vma);
> + vma_gap_update(vma);
> + spin_unlock(&vma->vm_mm->page_table_lock);
> +
> + perf_event_mmap(vma);
> }
> vma_unlock_anon_vma(vma);
> khugepaged_enter_vma_merge(vma, vma->vm_flags);
> validate_mm(vma->vm_mm);
> + return 0;
> +err:
> + vma_unlock_anon_vma(vma);
> return error;
> }
>
> @@ -2542,6 +2543,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
> {
> unsigned long end;
> struct vm_area_struct *vma, *prev, *last;
> + int error;
>
> if ((start & ~PAGE_MASK) || start> TASK_SIZE || len> TASK_SIZE-start)
> return -EINVAL;
> @@ -2570,8 +2572,6 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
> * places tmp vma above, and higher split_vma places tmp vma below.
> */
> if (start> vma->vm_start) {
> - int error;
> -
> /*
> * Make sure that map_count on return from munmap() will
> * not exceed its limit; but let map_count go just above
> @@ -2589,7 +2589,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
> /* Does it split the last one? */
> last = find_vma(mm, end);
> if (last && end> last->vm_start) {
> - int error = __split_vma(mm, last, end, 1);
> + error = __split_vma(mm, last, end, 1);
> if (error)
> return error;
> }
> --
> 1.9.3
>
>
>

--
Chen Gang

Open, share, and attitude like air, water, and life which God blessed
 		 	   		  
View attachment "0001-mm-mmap.c-Only-call-vma_unlock_anon_vm-for-failure-i.patch" of type "text/plain" (6565 bytes)

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