On Tue, Aug 07, 2012 at 05:51:05PM +0800, Xiao Guangrong wrote:
> We do too many things in hva_to_pfn, this patch reorganize the code,
> let it be better readable
>
> Signed-off-by: Xiao Guangrong <[email protected]>
> ---
> virt/kvm/kvm_main.c | 159
> +++++++++++++++++++++++++++++++--------------------
> 1 files changed, 97 insertions(+), 62 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 26ffc87..dd01bcb 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1043,83 +1043,118 @@ static inline int check_user_page_hwpoison(unsigned
> long addr)
> return rc == -EHWPOISON;
> }
>
> -static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
> - bool write_fault, bool *writable)
> +/*
> + * The atomic path to get the writable pfn which will be stored in @pfn,
> + * true indicates success, otherwise false is returned.
> + */
> +static bool hva_to_pfn_fast(unsigned long addr, bool atomic, bool *async,
> + bool write_fault, bool *writable, pfn_t *pfn)
> {
> struct page *page[1];
> - int npages = 0;
> - pfn_t pfn;
> + int npages;
>
> - /* we can do it either atomically or asynchronously, not both */
> - BUG_ON(atomic && async);
> + if (!(async || atomic))
> + return false;
>
> - BUG_ON(!write_fault && !writable);
> + npages = __get_user_pages_fast(addr, 1, 1, page);
> + if (npages == 1) {
> + *pfn = page_to_pfn(page[0]);
>
> - if (writable)
> - *writable = true;
> + if (writable)
> + *writable = true;
> + return true;
> + }
> +
> + return false;
> +}
>
> - if (atomic || async)
> - npages = __get_user_pages_fast(addr, 1, 1, page);
> +/*
> + * The slow path to get the pfn of the specified host virtual address,
> + * 1 indicates success, -errno is returned if error is detected.
> + */
> +static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
> + bool *writable, pfn_t *pfn)
> +{
> + struct page *page[1];
> + int npages = 0;
>
> - if (unlikely(npages != 1) && !atomic) {
> - might_sleep();
> + might_sleep();
>
> - if (writable)
> - *writable = write_fault;
> -
> - if (async) {
> - down_read(¤t->mm->mmap_sem);
> - npages = get_user_page_nowait(current, current->mm,
> - addr, write_fault, page);
> - up_read(¤t->mm->mmap_sem);
> - } else
> - npages = get_user_pages_fast(addr, 1, write_fault,
> - page);
> -
> - /* map read fault as writable if possible */
> - if (unlikely(!write_fault) && npages == 1) {
> - struct page *wpage[1];
> -
> - npages = __get_user_pages_fast(addr, 1, 1, wpage);
> - if (npages == 1) {
> - *writable = true;
> - put_page(page[0]);
> - page[0] = wpage[0];
> - }
> - npages = 1;
> + if (writable)
> + *writable = write_fault;
> +
> + if (async) {
> + down_read(¤t->mm->mmap_sem);
> + npages = get_user_page_nowait(current, current->mm,
> + addr, write_fault, page);
> + up_read(¤t->mm->mmap_sem);
> + } else
> + npages = get_user_pages_fast(addr, 1, write_fault,
> + page);
> + if (npages != 1)
> + return npages;
* Returns number of pages pinned. This may be fewer than the number
* requested. If nr_pages is 0 or negative, returns 0. If no pages
* were pinned, returns -errno.
*/
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
Current behaviour is
if (atomic || async)
npages = __get_user_pages_fast(addr, 1, 1, page);
if (npages != 1)
slow path retry;
The changes above change this, don't they?
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