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SubjectRe: [PATCH] mm: mmap: remove verify_mm_writelocked()
On Thu 08-11-18 12:48:56, Yangtao Li wrote:
> We should get rid of this function. It no longer serves its purpose.This
> is a historical artifact from 2005 where do_brk was called outside of
> the core mm.We do have a proper abstraction in vm_brk_flags and that one
> does the locking properly.So there is no need to use this function.
>
> Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/mmap.c | 16 ----------------
> 1 file changed, 16 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f7cd9cb966c0..1cee506494d2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2910,16 +2910,6 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
> return ret;
> }
>
> -static inline void verify_mm_writelocked(struct mm_struct *mm)
> -{
> -#ifdef CONFIG_DEBUG_VM
> - if (unlikely(down_read_trylock(&mm->mmap_sem))) {
> - WARN_ON(1);
> - up_read(&mm->mmap_sem);
> - }
> -#endif
> -}
> -
> /*
> * this is really a simplified "do_mmap". it only handles
> * anonymous maps. eventually we may be able to do some
> @@ -2946,12 +2936,6 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
> if (error)
> return error;
>
> - /*
> - * mm->mmap_sem is required to protect against another thread
> - * changing the mappings in case we sleep.
> - */
> - verify_mm_writelocked(mm);
> -
> /*
> * Clear old maps. this also does some error checking for us
> */
> --
> 2.17.0
>

--
Michal Hocko
SUSE Labs

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