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[86.156.84.164]) by smtp.googlemail.com with ESMTPSA id v9-20020a05600c444900b003f173be2ccfsm48948904wmn.2.2023.05.01.16.13.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 May 2023 16:13:59 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc: Jason Gunthorpe , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Christian Brauner , Richard Cochran , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Oleg Nesterov , Jason Gunthorpe , John Hubbard , Jan Kara , "Kirill A . Shutemov" , Pavel Begunkov , Mika Penttila , David Hildenbrand , Dave Chinner , Theodore Ts'o , Peter Xu , Lorenzo Stoakes Subject: [PATCH v6 1/3] mm/mmap: separate writenotify and dirty tracking logic Date: Tue, 2 May 2023 00:11:47 +0100 Message-Id: <72a90af5a9e4445a33ae44efa710f112c2694cb1.1682981880.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: MIME-Version: 1.0 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: vma_wants_writenotify() is specifically intended for setting PTE page table flags, accounting for existing PTE flag state and whether that might already be read-only while mixing this check with a check whether the filesystem performs dirty tracking. Separate out the notions of dirty tracking and a PTE write notify checking in order that we can invoke the dirty tracking check from elsewhere. Note that this change introduces a very small duplicate check of the separated out vm_ops_needs_writenotify(). This is necessary to avoid making vma_needs_dirty_tracking() needlessly complicated (e.g. passing a check_writenotify flag or having it assume this check was already performed). This is such a small check that it doesn't seem too egregious to do this. Signed-off-by: Lorenzo Stoakes Reviewed-by: John Hubbard Reviewed-by: Mika Penttilä Reviewed-by: Jan Kara Reviewed-by: Jason Gunthorpe --- include/linux/mm.h | 1 + mm/mmap.c | 36 +++++++++++++++++++++++++++--------- 2 files changed, 28 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 27ce77080c79..7b1d4e7393ef 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2422,6 +2422,7 @@ extern unsigned long move_page_tables(struct vm_area_struct *vma, #define MM_CP_UFFD_WP_ALL (MM_CP_UFFD_WP | \ MM_CP_UFFD_WP_RESOLVE) +bool vma_needs_dirty_tracking(struct vm_area_struct *vma); int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot); static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma) { diff --git a/mm/mmap.c b/mm/mmap.c index 5522130ae606..295c5f2e9bd9 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1475,6 +1475,31 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) } #endif /* __ARCH_WANT_SYS_OLD_MMAP */ +/* Do VMA operations imply write notify is required? */ +static bool vm_ops_needs_writenotify(const struct vm_operations_struct *vm_ops) +{ + return vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite); +} + +/* + * Does this VMA require the underlying folios to have their dirty state + * tracked? + */ +bool vma_needs_dirty_tracking(struct vm_area_struct *vma) +{ + /* Does the filesystem need to be notified? */ + if (vm_ops_needs_writenotify(vma->vm_ops)) + return true; + + /* Specialty mapping? */ + if (vma->vm_flags & VM_PFNMAP) + return false; + + /* Can the mapping track the dirty pages? */ + return vma->vm_file && vma->vm_file->f_mapping && + mapping_can_writeback(vma->vm_file->f_mapping); +} + /* * Some shared mappings will want the pages marked read-only * to track write events. If so, we'll downgrade vm_page_prot @@ -1484,14 +1509,13 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot) { vm_flags_t vm_flags = vma->vm_flags; - const struct vm_operations_struct *vm_ops = vma->vm_ops; /* If it was private or non-writable, the write bit is already clear */ if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED))) return 0; /* The backer wishes to know when pages are first written to? */ - if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite)) + if (vm_ops_needs_writenotify(vma->vm_ops)) return 1; /* The open routine did something to the protections that pgprot_modify @@ -1511,13 +1535,7 @@ int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot) if (userfaultfd_wp(vma)) return 1; - /* Specialty mapping? */ - if (vm_flags & VM_PFNMAP) - return 0; - - /* Can the mapping track the dirty pages? */ - return vma->vm_file && vma->vm_file->f_mapping && - mapping_can_writeback(vma->vm_file->f_mapping); + return vma_needs_dirty_tracking(vma); } /*