Hi Peter,
Thank you so much for reviewing!
On 2/9/23 2:12 AM, Peter Xu wrote:
> On Thu, Feb 02, 2023 at 04:29:10PM +0500, Muhammad Usama Anjum wrote:
>> Add new WP Async mode (UFFD_FEATURE_WP_ASYNC) which resolves the page
>> faults on its own. It can be used to track that which pages have been
>> written-to from the time the pages were write-protected. It is very
>> efficient way to track the changes as uffd is by nature pte/pmd based.
>>
>> UFFD synchronous WP sends the page faults to the userspace where the
>> pages which have been written-to can be tracked. But it is not efficient.
>> This is why this asynchronous version is being added. After setting the
>> WP Async, the pages which have been written to can be found in the pagemap
>> file or information can be obtained from the PAGEMAP_IOCTL.
>>
>> Suggested-by: Peter Xu <peterx@xxxxxxxxxx>
>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
>> ---
>> Changes in v10:
>> - Build fix
>> - Update comments and add error condition to return error from uffd
>> register if hugetlb pages are present when wp async flag is set
>>
>> Changes in v9:
>> - Correct the fault resolution with code contributed by Peter
>>
>> Changes in v7:
>> - Remove UFFDIO_WRITEPROTECT_MODE_ASYNC_WP and add UFFD_FEATURE_WP_ASYNC
>> - Handle automatic page fault resolution in better way (thanks to Peter)
>>
>> update to wp async
>>
>> uffd wp async
>> ---
>> fs/userfaultfd.c | 20 ++++++++++++++++++--
>> include/linux/userfaultfd_k.h | 11 +++++++++++
>> include/uapi/linux/userfaultfd.h | 10 +++++++++-
>> mm/memory.c | 23 ++++++++++++++++++++---
>> 4 files changed, 58 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
>> index 15a5bf765d43..422f2530c63e 100644
>> --- a/fs/userfaultfd.c
>> +++ b/fs/userfaultfd.c
>> @@ -1422,10 +1422,15 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
>> goto out_unlock;
>>
>> /*
>> - * Note vmas containing huge pages
>> + * Note vmas containing huge pages. Hugetlb isn't supported
>> + * with UFFD_FEATURE_WP_ASYNC.
>> */
>
> Need to set "ret = -EINVAL;" here. Or..
Will fix in next version.
>
>> - if (is_vm_hugetlb_page(cur))
>> + if (is_vm_hugetlb_page(cur)) {
>> + if (ctx->features & UFFD_FEATURE_WP_ASYNC)
>> + goto out_unlock;
>
> .. it'll return -EBUSY, which does not sound like the right errcode here.
>
>> +
>
> Drop this empty line?
>
>> basic_ioctls = true;
>> + }
>>
>> found = true;
>> }
>
> Other than that looks good, thanks.
Thank you so much! This wouldn't have been possible without your help.
>
--
BR,
Muhammad Usama Anjum
