Re: [PATCH] fs: use kmalloc() to allocate fdmem if possible

Avi Kivity
2010-05-02T17:31:54Z

On 05/02/2010 07:46 PM, Changli Gao wrote:
> use kmalloc() to allocate fdmem if possible.
>
> vmalloc() is used as a fallback solution for fdmem allocation. Two members are
> added into the hole of the structure fdtable to indicate if vmalloc() is used
> or not.
>
>
> diff --git a/fs/file.c b/fs/file.c
> index 34bb7f7..f71dd85 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -39,28 +39,34 @@ int sysctl_nr_open_max = 1024 * 1024; /* raised later */
> */
> static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
>
> -static inline void * alloc_fdmem(unsigned int size)
> +static inline void *alloc_fdmem(unsigned int size, unsigned short *use_vmalloc)
> {
> - if (size<= PAGE_SIZE)
> - return kmalloc(size, GFP_KERNEL);
> - else
> - return vmalloc(size);
> + void *data;
> +
> + data = kmalloc(size, GFP_KERNEL);
> + if (data != NULL) {
> + *use_vmalloc = 0;
> + return data;
> + }
> + *use_vmalloc = 1;
> +
> + return vmalloc(size);
> }
>

Perhaps vmalloc() should do this by itself? vfree() can examine the
pointer and call kfree() if it isn't within the vmalloc address range.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.