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Mon, 28 Oct 2024 21:33:39 +0800 Message-ID: <127d4a00-29cc-4b45-aa96-eea4e0adaed2@huawei.com> Date: Mon, 28 Oct 2024 21:33:38 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] mm: use aligned address in clear_gigantic_page() To: David Hildenbrand , Andrew Morton CC: Matthew Wilcox , Muchun Song , "Huang, Ying" , References: <20241026054307.3896926-1-wangkefeng.wang@huawei.com> <54f5f3ee-8442-4c49-ab4e-c46e8db73576@huawei.com> <4219a788-52ad-4d80-82e6-35a64c980d50@redhat.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: <4219a788-52ad-4d80-82e6-35a64c980d50@redhat.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemf100008.china.huawei.com (7.185.36.138) X-Stat-Signature: 4ky9ghxrfp43h6zinueu7dpz3bcut49s X-Rspamd-Queue-Id: 4F03D180013 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1730122424-548974 X-HE-Meta: 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 Jd7LcTj7 TeCfVO9PDvFN5JwteaoTjwuC+Q0mtw502HB0O8DAoOFR6n0QXEKeWluQEwuBdmS55mqziSflZyG0lPVZW8vMqF/GtXuDOovZ2t4FgqMkQjt0Ji7ov6ra/f/4DHZ320RJYzxAXPqJdoOTsqf3rcJcGSsKfof1prSThUCAawDeYtFJ4SAPqVVnCwP8zeK9KdF+C8thqytWJYOXG6J23F/qxlbZ+DlW61P+XfpbsZBcJyW+VY+kkzcIfF8OJ4dK/eYXWuYbn8iPgC2Mz+tw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/10/28 21:14, David Hildenbrand wrote: > On 28.10.24 13:52, Kefeng Wang wrote: >> >> >> On 2024/10/28 18:00, David Hildenbrand wrote: >>> On 26.10.24 07:43, Kefeng Wang wrote: >>>> When clearing gigantic page, it zeros page from the first page to the >>>> last page, if directly passing addr_hint which maybe not the address >>>> of the first page of folio, then some archs could flush the wrong cache >>>> if it does use the addr_hint as a hint. For non-gigantic page, it >>>> calculates the base address inside, even passed the wrong addr_hint, it >>>> only has performance impact as the process_huge_page() wants to process >>>> target page last to keep its cache lines hot), no functional impact. >>>> >>>> Let's pass the real accessed address to folio_zero_user() and use the >>>> aligned address in clear_gigantic_page() to fix it. >>>> >>>> Fixes: 78fefd04c123 ("mm: memory: convert clear_huge_page() to >>>> folio_zero_user()") >>>> Signed-off-by: Kefeng Wang >>>> --- >>>> v2: >>>> - update changelog to clarify the impact, per Andrew >>>> >>>>    fs/hugetlbfs/inode.c | 2 +- >>>>    mm/memory.c          | 1 + >>>>    2 files changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c >>>> index a4441fb77f7c..a5ea006f403e 100644 >>>> --- a/fs/hugetlbfs/inode.c >>>> +++ b/fs/hugetlbfs/inode.c >>>> @@ -825,7 +825,7 @@ static long hugetlbfs_fallocate(struct file *file, >>>> int mode, loff_t offset, >>>>                error = PTR_ERR(folio); >>>>                goto out; >>>>            } >>>> -        folio_zero_user(folio, ALIGN_DOWN(addr, hpage_size)); >>>> +        folio_zero_user(folio, addr); >>>>            __folio_mark_uptodate(folio); >>>>            error = hugetlb_add_to_page_cache(folio, mapping, index); >>>>            if (unlikely(error)) { >>>> diff --git a/mm/memory.c b/mm/memory.c >>>> index 75c2dfd04f72..ef47b7ea5ddd 100644 >>>> --- a/mm/memory.c >>>> +++ b/mm/memory.c >>>> @@ -6821,6 +6821,7 @@ static void clear_gigantic_page(struct folio >>>> *folio, unsigned long addr, >>>>        int i; >>>>        might_sleep(); >>>> +    addr = ALIGN_DOWN(addr, folio_size(folio)); >>> >>> Right, that's what's effectively done in a very bad way in >>> process_huge_page() >>> >>> unsigned long addr = addr_hint & >>>                ~(((unsigned long)nr_pages << PAGE_SHIFT) - 1); >>> >>> >>> That should all be cleaned up ... process_huge_page() likely shouldn't >> >> Yes, let's fix the bug firstly, >> >>> be even consuming "nr_pages". >> >> No sure about this part, it uses nr_pages as the end and calculate the >> 'base'. > > It should be using folio_nr_pages(). But process_huge_page() without an explicit folio argument, I'd like to move the aligned address calculate into the folio_zero_user and copy_user_large_folio(will rename it to folio_copy_user()) in the following cleanup patches, or do it in the fix patches?