Re: possible deadlock in shmem_fallocate (4)

[Eric Biggers]

On Tue, Jul 14, 2020 at 11:32:52AM +0800, Hillf Danton wrote:
> 
> Add FALLOC_FL_NOBLOCK and on the shmem side try to lock inode upon the
> new flag. And the overall upside is to keep the current gfp either in
> the khugepaged context or not.
> 
> --- a/include/uapi/linux/falloc.h
> +++ b/include/uapi/linux/falloc.h
> @@ -77,4 +77,6 @@
>   */
>  #define FALLOC_FL_UNSHARE_RANGE		0x40
>  
> +#define FALLOC_FL_NOBLOCK		0x80
> +

You can't add a new UAPI flag to fix a kernel-internal problem like this.

- Eric