Re: [PATCH][RFC] add MAP_UNLOCKED mmap flag

[Frederik Deweerdt]

Hello Gleb,

On Tue, Oct 06, 2009 at 11:51:11AM +0200, Gleb Natapov wrote:
> If application does mlockall(MCL_FUTURE) it is no longer possible to
> mmap file bigger than main memory or allocate big area of anonymous
> memory. Sometimes it is desirable to lock everything related to program
> execution into memory, but still be able to mmap big file or allocate
> huge amount of memory and allow OS to swap them on demand. MAP_UNLOCKED
> allows to do that.
> 
> Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
> diff --git a/include/asm-generic/mman.h b/include/asm-generic/mman.h
> index 32c8bd6..0ab4c74 100644
> --- a/include/asm-generic/mman.h
> +++ b/include/asm-generic/mman.h
> @@ -12,6 +12,7 @@
>  #define MAP_NONBLOCK	0x10000		/* do not block on IO */
>  #define MAP_STACK	0x20000		/* give out an address that is best suited for process/thread stacks */
>  #define MAP_HUGETLB	0x40000		/* create a huge page mapping */
> +#define MAP_UNLOKED	0x80000         /* pages are unlocked */
                 ^^^
You're missing a 'C' here and below. Also '/* force page unlocking */'
seems a better comment?

Regards,
Frederik
>  
>  #define MCL_CURRENT	1		/* lock all current mappings */
>  #define MCL_FUTURE	2		/* lock all future mappings */
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 73f5e4b..7c2abdb 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -985,6 +985,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
>  		if (!can_do_mlock())
>  			return -EPERM;
>  
> +        if (flags & MAP_UNLOKED)
> +                vm_flags &= ~VM_LOCKED;
> +
>  	/* mlock MCL_FUTURE? */
>  	if (vm_flags & VM_LOCKED) {
>  		unsigned long locked, lock_limit;
> --
> 			Gleb.
> --
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