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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-432da2800absm151820395e9.25.2024.11.18.01.38.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Nov 2024 01:38:30 -0800 (PST) Message-ID: <15f665b4-2d33-41ca-ac50-fafe24ade32f@redhat.com> Date: Mon, 18 Nov 2024 10:38:29 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 1/2] KVM: guest_memfd: Convert .free_folio() to .release_folio() To: Elliot Berman Cc: Paolo Bonzini , Andrew Morton , Sean Christopherson , Fuad Tabba , Ackerley Tng , Mike Rapoport , "H. Peter Anvin" , Matthew Wilcox , James Gowans , linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20241113-guestmem-library-v3-0-71fdee85676b@quicinc.com> <20241113-guestmem-library-v3-1-71fdee85676b@quicinc.com> <20241115121119110-0800.eberman@hu-eberman-lv.qualcomm.com> From: David Hildenbrand Content-Language: en-US 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: <20241115121119110-0800.eberman@hu-eberman-lv.qualcomm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 15.11.24 21:13, Elliot Berman wrote: > On Fri, Nov 15, 2024 at 11:58:59AM +0100, David Hildenbrand wrote: >> On 15.11.24 11:58, David Hildenbrand wrote: >>> On 13.11.24 23:34, Elliot Berman wrote: >>>> When guest_memfd becomes a library, a callback will need to be made to >>>> the owner (KVM SEV) to transition pages back to hypervisor-owned/shared >>>> state. This is currently being done as part of .free_folio() address >>>> space op, but this callback shouldn't assume that the mapping still >>>> exists. guest_memfd library will need the mapping to still exist to look >>>> up its operations table. >>> >>> I assume you mean, that the mapping is no longer set for the folio (it >>> sure still exists, because we are getting a callback from it :) )? >>> >>> Staring at filemap_remove_folio(), this is exactly what happens: >>> >>> We remember folio->mapping, call __filemap_remove_folio(), and then call >>> filemap_free_folio() where we zap folio->mapping via page_cache_delete(). >>> >>> Maybe it's easier+cleaner to also forward the mapping to the >>> free_folio() callback, just like we do with filemap_free_folio()? Would >>> that help? >>> >>> CCing Willy if that would be reasonable extension of the free_folio >>> callback. >>> > > I like this approach too. It would avoid the checks we have to do in the > invalidate_folio() callback and is cleaner. It really should be fairly simple Documentation/filesystems/locking.rst | 2 +- fs/nfs/dir.c | 9 +++++---- fs/orangefs/inode.c | 3 ++- include/linux/fs.h | 2 +- mm/filemap.c | 2 +- mm/secretmem.c | 3 ++- virt/kvm/guest_memfd.c | 3 ++- 7 files changed, 14 insertions(+), 10 deletions(-) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index f5e3676db954b..f1a20ad5edbee 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -258,7 +258,7 @@ prototypes:: sector_t (*bmap)(struct address_space *, sector_t); void (*invalidate_folio) (struct folio *, size_t start, size_t len); bool (*release_folio)(struct folio *, gfp_t); - void (*free_folio)(struct folio *); + void (*free_folio)(struct address_space *, struct folio *); int (*direct_IO)(struct kiocb *, struct iov_iter *iter); int (*migrate_folio)(struct address_space *, struct folio *dst, struct folio *src, enum migrate_mode); diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 492cffd9d3d84..f7da6d7496b06 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -218,7 +218,8 @@ static void nfs_readdir_folio_init_array(struct folio *folio, u64 last_cookie, /* * we are freeing strings created by nfs_add_to_readdir_array() */ -static void nfs_readdir_clear_array(struct folio *folio) +static void nfs_readdir_clear_array(struct address_space *mapping, + struct folio *folio) { struct nfs_cache_array *array; unsigned int i; @@ -233,7 +234,7 @@ static void nfs_readdir_clear_array(struct folio *folio) static void nfs_readdir_folio_reinit_array(struct folio *folio, u64 last_cookie, u64 change_attr) { - nfs_readdir_clear_array(folio); + nfs_readdir_clear_array(folio->mapping, folio); nfs_readdir_folio_init_array(folio, last_cookie, change_attr); } @@ -249,7 +250,7 @@ nfs_readdir_folio_array_alloc(u64 last_cookie, gfp_t gfp_flags) static void nfs_readdir_folio_array_free(struct folio *folio) { if (folio) { - nfs_readdir_clear_array(folio); + nfs_readdir_clear_array(folio->mapping, folio); folio_put(folio); } } @@ -391,7 +392,7 @@ static void nfs_readdir_folio_init_and_validate(struct folio *folio, u64 cookie, if (folio_test_uptodate(folio)) { if (nfs_readdir_folio_validate(folio, cookie, change_attr)) return; - nfs_readdir_clear_array(folio); + nfs_readdir_clear_array(folio->mapping, folio); } nfs_readdir_folio_init_array(folio, cookie, change_attr); folio_mark_uptodate(folio); diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c index aae6d2b8767df..d936694b8e91f 100644 --- a/fs/orangefs/inode.c +++ b/fs/orangefs/inode.c @@ -470,7 +470,8 @@ static bool orangefs_release_folio(struct folio *folio, gfp_t foo) return !folio_test_private(folio); } -static void orangefs_free_folio(struct folio *folio) +static void orangefs_free_folio(struct address_space *mapping, + struct folio *folio) { kfree(folio_detach_private(folio)); } diff --git a/include/linux/fs.h b/include/linux/fs.h index 3559446279c15..4dd4013541c1b 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -417,7 +417,7 @@ struct address_space_operations { sector_t (*bmap)(struct address_space *, sector_t); void (*invalidate_folio) (struct folio *, size_t offset, size_t len); bool (*release_folio)(struct folio *, gfp_t); - void (*free_folio)(struct folio *folio); + void (*free_folio)(struct address_space *, struct folio *folio); ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter); /* * migrate the contents of a folio to the specified target. If diff --git a/mm/filemap.c b/mm/filemap.c index e582a1545d2ae..86f975ba80746 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -239,7 +239,7 @@ void filemap_free_folio(struct address_space *mapping, struct folio *folio) free_folio = mapping->a_ops->free_folio; if (free_folio) - free_folio(folio); + free_folio(mapping, folio); if (folio_test_large(folio)) refs = folio_nr_pages(folio); diff --git a/mm/secretmem.c b/mm/secretmem.c index 399552814fd0f..1d2ed3391734d 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -152,7 +152,8 @@ static int secretmem_migrate_folio(struct address_space *mapping, return -EBUSY; } -static void secretmem_free_folio(struct folio *folio) +static void secretmem_free_folio(struct address_space *mapping, + struct folio *folio) { set_direct_map_default_noflush(&folio->page); folio_zero_segment(folio, 0, folio_size(folio)); diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 8f079a61a56db..573946c4fff51 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -353,7 +353,8 @@ static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *fol } #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE -static void kvm_gmem_free_folio(struct folio *folio) +static void kvm_gmem_free_folio(struct address_space *mapping, + struct folio *folio) { struct page *page = folio_page(folio, 0); kvm_pfn_t pfn = page_to_pfn(page); -- 2.47.0 -- Cheers, David / dhildenb