From mboxrd@z Thu Jan 1 00:00:00 1970 From: Baolin Wang Date: Sun, 08 May 2022 13:09:55 +0000 Subject: Re: [PATCH v2 1/3] mm: change huge_ptep_clear_flush() to return the original pte Message-Id: List-Id: References: <012a484019e7ad77c39deab0af52a6755d8438c8.1652002221.git.baolin.wang@linux.alibaba.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Muchun Song Cc: akpm@linux-foundation.org, mike.kravetz@oracle.com, catalin.marinas@arm.com, will@kernel.org, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org On 5/8/2022 7:09 PM, Muchun Song wrote: > On Sun, May 08, 2022 at 05:36:39PM +0800, Baolin Wang wrote: >> It is incorrect to use ptep_clear_flush() to nuke a hugetlb page >> table when unmapping or migrating a hugetlb page, and will change >> to use huge_ptep_clear_flush() instead in the following patches. >> >> So this is a preparation patch, which changes the huge_ptep_clear_flush() >> to return the original pte to help to nuke a hugetlb page table. >> >> Signed-off-by: Baolin Wang >> Acked-by: Mike Kravetz > > Reviewed-by: Muchun Song Thanks for reviewing. > > But one nit below: > > [...] >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 8605d7e..61a21af 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -5342,7 +5342,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, >> ClearHPageRestoreReserve(new_page); >> >> /* Break COW or unshare */ >> - huge_ptep_clear_flush(vma, haddr, ptep); >> + (void)huge_ptep_clear_flush(vma, haddr, ptep); > > Why add a "(void)" here? Is there any warning if no "(void)"? > IIUC, I think we can remove this, right? I did not meet any warning without the casting, but this is per Mike's comment[1] to make the code consistent with other functions casting to void type explicitly in hugetlb.c file. [1] https://lore.kernel.org/all/495c4ebe-a5b4-afb6-4cb0-956c1b18d0cc@oracle.com/