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Howlett" , Mike Rapoport , Lorenzo Stoakes , Axel Rasmussen Subject: Re: [PATCH 4/4] mm: Apply vm_uffd_ops API to core mm Message-ID: References: <20250620190342.1780170-1-peterx@redhat.com> <20250620190342.1780170-5-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: RNOkAg7q_wSeJIrYdslhQ45ZEIjPScnq8hjN5E5q2oI_1750886482 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Stat-Signature: j4w91iokc3pfysirqwb35um4h9kd3e34 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: DC01C4000D X-Rspam-User: X-HE-Tag: 1750886484-292497 X-HE-Meta: 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 UUgBWTGH odr7V9wns6IXtD7Td85kibhKYqvy93drEnx1mYFIEatjwaGk9ra/C7z16E4gBUeJZ96/u+O5APlU88SE11Wacnf5ET5U5L42Mg3n40R0LPWpxBN1sP2vIxRuKR/UMPxxHtYtJOLzat9goRzh4XgapcneXc2/WBmyvBWxeVFrte0yQ6sGfXYgcqIRgKc4G9gDRkZA6cK/r1Zq1X3sN3nhe5iVjoMENbs6cmFhFxItpDm4b8rQHemLSIgXDT5q6GP8ZzXyr58OH+2pElhCf8QGZ4X706UQTf2oka/knKwdP1C58AgUbiOtvJ7U76gOQCZaukFUBylrRJxyx8XSX4z78Fny33A+SslupMuiPA84fTjSnvqb8k/aHqMCpX6OuHb6lIVhNyr0I6J+VszfsTePT5K2fvp1c+uWH4ARhdJ/4rF7dxxV6GLLeNftf1XfEhON/FZXxGeYDqc9VjB4= 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 Wed, Jun 25, 2025 at 01:31:49PM -0700, James Houghton wrote: > > -static inline bool vma_can_userfault(struct vm_area_struct *vma, > > - unsigned long vm_flags, > > - bool wp_async) > > +static inline const vm_uffd_ops *vma_get_uffd_ops(struct vm_area_struct *vma) > > { > > - vm_flags &= __VM_UFFD_FLAGS; > > - > > - if (vma->vm_flags & VM_DROPPABLE) > > - return false; > > - > > - if ((vm_flags & VM_UFFD_MINOR) && > > - (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma))) > > - return false; > > - > > - /* > > - * If wp async enabled, and WP is the only mode enabled, allow any > > - * memory type. > > - */ > > - if (wp_async && (vm_flags == VM_UFFD_WP)) > > - return true; > > - > > -#ifndef CONFIG_PTE_MARKER_UFFD_WP > > - /* > > - * If user requested uffd-wp but not enabled pte markers for > > - * uffd-wp, then shmem & hugetlbfs are not supported but only > > - * anonymous. > > - */ > > - if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma)) > > - return false; > > -#endif > > Hi Peter, > > Thanks for this cleanup! > > It looks like the above two checks, the wp-async one and the PTE > marker check, have been reordered in this patch. Does this result in a > functional difference? > > The rest of this series looks fine to me. :) Thanks for the very careful review, James! Yes that's a small tweak I did when moving. I don't expect to have any functional change. Maybe I should at least mention that in the commit log. Here I did the movement because fundamentally wp_async depends on the pte markers, so it may be slightly more intuitive to check pte markers first, rejecting any form of file wr-protect traps. Otherwise it may looks like we could return the true for wp_async==true too early. In reality IIUC it can't happen. For example, currently userfaultfd_api() has: #ifndef CONFIG_PTE_MARKER_UFFD_WP uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM; uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED; uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC; #endif So when wp_async can be true above, pte markers must be compiled.. IOW, above code clip should work identically with below lines: #ifdef CONFIG_PTE_MARKER_UFFD_WP if (wp_async && (vm_flags == VM_UFFD_WP)) return true; #endif #ifndef CONFIG_PTE_MARKER_UFFD_WP if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma)) return false; #endif Then it means both chunks of code cannot be compiled together. The order shouldn't matter. But maybe I should just move it back as before, to save the explain and confusions. Let me know if you have any preference. Thanks, -- Peter Xu