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[2003:d8:2f09:f500:a38f:d086:59d4:9df]) by smtp.gmail.com with ESMTPSA id j30-20020adfb31e000000b003197869bcd7sm5163464wrd.13.2023.11.13.02.33.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Nov 2023 02:33:44 -0800 (PST) Message-ID: <0f05cade-c75e-4605-8e22-9fb916c622b0@redhat.com> Date: Mon, 13 Nov 2023 11:33:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] mm/gup: Introduce pin_user_pages_fd() for pinning shmem/hugetlbfs file pages (v2) To: Vivek Kasireddy , dri-devel@lists.freedesktop.org, linux-mm@kvack.org Cc: Daniel Vetter , Mike Kravetz , Hugh Dickins , Peter Xu , Gerd Hoffmann , Dongwon Kim , Junxiao Chang , Jason Gunthorpe References: <20231106061541.507116-1-vivek.kasireddy@intel.com> <20231106061541.507116-2-vivek.kasireddy@intel.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20231106061541.507116-2-vivek.kasireddy@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: EC75A8000B X-Stat-Signature: 6oe8zcr8qcqfhw8j94um43hybic7ntp4 X-Rspam-User: X-HE-Tag: 1699871628-278663 X-HE-Meta: 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 TRB5l+F/ 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 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 06.11.23 07:15, Vivek Kasireddy wrote: > For drivers that would like to longterm-pin the pages associated > with a file, the pin_user_pages_fd() API provides an option to > not only pin the pages via FOLL_PIN but also to check and migrate > them if they reside in movable zone or CMA block. This API > currently works with files that belong to either shmem or hugetlbfs. > Files belonging to other filesystems are rejected for now. > > The pages need to be located first before pinning them via FOLL_PIN. > If they are found in the page cache, they can be immediately pinned. > Otherwise, they need to be allocated using the filesystem specific > APIs and then pinned. > > v2: > - Drop gup_flags and improve comments and commit message (David) > - Allocate a page if we cannot find in page cache for the hugetlbfs > case as well (David) > - Don't unpin pages if there is a migration related failure (David) > - Drop the unnecessary nr_pages <= 0 check (Jason) > - Have the caller of the API pass in file * instead of fd (Jason) > > Cc: David Hildenbrand > Cc: Daniel Vetter > Cc: Mike Kravetz > Cc: Hugh Dickins > Cc: Peter Xu > Cc: Gerd Hoffmann > Cc: Dongwon Kim > Cc: Junxiao Chang > Suggested-by: Jason Gunthorpe > Signed-off-by: Vivek Kasireddy > --- > include/linux/mm.h | 2 + > mm/gup.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 101 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index bf5d0b1b16f4..f6cc17b14653 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2457,6 +2457,8 @@ long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > struct page **pages, unsigned int gup_flags); > long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > struct page **pages, unsigned int gup_flags); > +long pin_user_pages_fd(struct file *file, pgoff_t start, > + unsigned long nr_pages, struct page **pages); > > int get_user_pages_fast(unsigned long start, int nr_pages, > unsigned int gup_flags, struct page **pages); > diff --git a/mm/gup.c b/mm/gup.c > index 2f8a2d89fde1..d30b9dfebbb6 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -3400,3 +3400,102 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > &locked, gup_flags); > } > EXPORT_SYMBOL(pin_user_pages_unlocked); > + > +static struct page *alloc_file_page(struct file *file, pgoff_t idx) > +{ > + struct page *page = ERR_PTR(-ENOMEM); > + struct folio *folio; > + int err; > + > + if (shmem_file(file)) > + return shmem_read_mapping_page(file->f_mapping, idx); > + As the build reports indicate, this might have to be fenced with #ifdef CONFIG_HUGETLB_PAGE > + folio = alloc_hugetlb_folio_nodemask(hstate_file(file), > + NUMA_NO_NODE, > + NULL, > + GFP_USER); > + if (folio && folio_try_get(folio)) { > + page = &folio->page; > + err = hugetlb_add_to_page_cache(folio, file->f_mapping, idx); > + if (err) { > + folio_put(folio); > + free_huge_folio(folio); > + page = ERR_PTR(err); > + } > + } > + > + return page; > +} > + > +/** > + * pin_user_pages_fd() - pin user pages associated with a file > + * @file: the file whose pages are to be pinned > + * @start: starting file offset > + * @nr_pages: number of pages from start to pin > + * @pages: array that receives pointers to the pages pinned. > + * Should be at-least nr_pages long. > + * > + * Attempt to pin pages associated with a file that belongs to either shmem > + * or hugetlbfs. The pages are either found in the page cache or allocated nit: s/hugetlbfs/hugetlb/ > + * if necessary. Once the pages are located, they are all pinned via FOLL_PIN. > + * And, these pinned pages need to be released using unpin_user_pages() or > + * unpin_user_page(). > + * It might be reasonable to add that the behavior mimics FOLL_LONGTERM semantics: the page may be held for an indefinite time period _often_ under userspace control. > + * Returns number of pages pinned. This would be equal to the number of > + * pages requested. If no pages were pinned, it returns -errno. > + */ > +long pin_user_pages_fd(struct file *file, pgoff_t start, > + unsigned long nr_pages, struct page **pages) > +{ > + struct page *page; > + unsigned int flags, i; > + long ret; > + > + if (start < 0) > + return -EINVAL; > + > + if (!file) > + return -EINVAL; > + > + if (!shmem_file(file) && !is_file_hugepages(file)) > + return -EINVAL; > + > + flags = memalloc_pin_save(); > + do { > + for (i = 0; i < nr_pages; i++) { > + /* > + * In most cases, we should be able to find the page > + * in the page cache. If we cannot find it, we try to > + * allocate one and add it to the page cache. > + */ > + page = find_get_page_flags(file->f_mapping, > + start + i, > + FGP_ACCESSED); > + if (!page) { > + page = alloc_file_page(file, start + i); > + if (IS_ERR(page)) { > + ret = PTR_ERR(page); > + goto err; > + } > + } > + ret = try_grab_page(page, FOLL_PIN); > + if (unlikely(ret)) > + goto err; > + > + pages[i] = page; > + put_page(pages[i]); > + } > + > + ret = check_and_migrate_movable_pages(nr_pages, pages); > + } while (ret == -EAGAIN); > + > + memalloc_pin_restore(flags); > + return ret ? ret : nr_pages; > +err: missing memalloc_pin_restore() ? > + while (i > 0 && pages[--i]) > + unpin_user_page(pages[i]); So if any pages[] would be 0, we would stop completely? Shouldn't this be something like: while (i-- > 0) if (pages[i]) unpin_user_page(pages[i]); -- Cheers, David / dhildenb