From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Kravetz Date: Tue, 30 Aug 2022 16:44:18 +0000 Subject: Re: [PATCH] hugetlb: simplify hugetlb handling in follow_page_mask Message-Id: List-Id: References: <20220829234053.159158-1-mike.kravetz@oracle.com> <57c8f032-e48a-bacb-7922-3e2cc10dc0d2@linux.alibaba.com> In-Reply-To: <57c8f032-e48a-bacb-7922-3e2cc10dc0d2@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Baolin Wang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, inuxppc-dev@lists.ozlabs.org, linux-ia64@vger.kernel.org, David Hildenbrand , "Aneesh Kumar K . V" , Naoya Horiguchi , Michael Ellerman , Muchun Song , Andrew Morton On 08/30/22 09:06, Baolin Wang wrote: > Hi Mike, > > On 8/30/2022 7:40 AM, Mike Kravetz wrote: > > During discussions of this series [1], it was suggested that hugetlb > > handling code in follow_page_mask could be simplified. At the beginning > > of follow_page_mask, there currently is a call to follow_huge_addr which > > 'may' handle hugetlb pages. ia64 is the only architecture which provides > > a follow_huge_addr routine that does not return error. Instead, at each > > level of the page table a check is made for a hugetlb entry. If a hugetlb > > entry is found, a call to a routine associated with that entry is made. > > > > Currently, there are two checks for hugetlb entries at each page table > > level. The first check is of the form: > > if (p?d_huge()) > > page = follow_huge_p?d(); > > the second check is of the form: > > if (is_hugepd()) > > page = follow_huge_pd(). > > > > We can replace these checks, as well as the special handling routines > > such as follow_huge_p?d() and follow_huge_pd() with a single routine to > > handle hugetlb vmas. > > > > A new routine hugetlb_follow_page_mask is called for hugetlb vmas at the > > beginning of follow_page_mask. hugetlb_follow_page_mask will use the > > existing routine huge_pte_offset to walk page tables looking for hugetlb > > entries. huge_pte_offset can be overwritten by architectures, and already > > handles special cases such as hugepd entries. > > Could you also mention that this patch will fix the lock issue for > CONT-PTE/PMD hugetlb by changing to use huge_pte_lock()? which will help > people to understand the issue. Will update message in v2. Thanks for taking a look! > > Otherwise the changes look good to me. > Reviewed-by: Baolin Wang -- Mike Kravetz