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Wed, 15 Jan 2025 04:17:29 -0800 (PST) Date: Wed, 15 Jan 2025 12:17:29 +0000 From: Wei Yang To: Suren Baghdasaryan Cc: Wei Yang , akpm@linux-foundation.org, peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v9 16/17] mm: make vma cache SLAB_TYPESAFE_BY_RCU Message-ID: <20250115121729.al7sxmpqutmhaxod@master> Reply-To: Wei Yang References: <20250111042604.3230628-1-surenb@google.com> <20250111042604.3230628-17-surenb@google.com> <20250115022703.hqbqdqawvqgrfgxb@master> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) On Tue, Jan 14, 2025 at 07:15:05PM -0800, Suren Baghdasaryan wrote: >On Tue, Jan 14, 2025 at 6:27 PM Wei Yang wrote: >> >> On Fri, Jan 10, 2025 at 08:26:03PM -0800, Suren Baghdasaryan wrote: >> >> >diff --git a/kernel/fork.c b/kernel/fork.c >> >index 9d9275783cf8..151b40627c14 100644 >> >--- a/kernel/fork.c >> >+++ b/kernel/fork.c >> >@@ -449,6 +449,42 @@ struct vm_area_struct *vm_area_alloc(struct mm_struct *mm) >> > return vma; >> > } >> > >> >+static void vm_area_init_from(const struct vm_area_struct *src, >> >+ struct vm_area_struct *dest) >> >+{ >> >+ dest->vm_mm = src->vm_mm; >> >+ dest->vm_ops = src->vm_ops; >> >+ dest->vm_start = src->vm_start; >> >+ dest->vm_end = src->vm_end; >> >+ dest->anon_vma = src->anon_vma; >> >+ dest->vm_pgoff = src->vm_pgoff; >> >+ dest->vm_file = src->vm_file; >> >+ dest->vm_private_data = src->vm_private_data; >> >+ vm_flags_init(dest, src->vm_flags); >> >+ memcpy(&dest->vm_page_prot, &src->vm_page_prot, >> >+ sizeof(dest->vm_page_prot)); >> >+ /* >> >+ * src->shared.rb may be modified concurrently when called from >> >+ * dup_mmap(), but the clone will reinitialize it. >> >+ */ >> >+ data_race(memcpy(&dest->shared, &src->shared, sizeof(dest->shared))); >> >+ memcpy(&dest->vm_userfaultfd_ctx, &src->vm_userfaultfd_ctx, >> >+ sizeof(dest->vm_userfaultfd_ctx)); >> >+#ifdef CONFIG_ANON_VMA_NAME >> >+ dest->anon_name = src->anon_name; >> >+#endif >> >+#ifdef CONFIG_SWAP >> >+ memcpy(&dest->swap_readahead_info, &src->swap_readahead_info, >> >+ sizeof(dest->swap_readahead_info)); >> >+#endif >> >+#ifndef CONFIG_MMU >> >+ dest->vm_region = src->vm_region; >> >+#endif >> >+#ifdef CONFIG_NUMA >> >+ dest->vm_policy = src->vm_policy; >> >+#endif >> >+} >> >> Would this be difficult to maintain? We should make sure not miss or overwrite >> anything. > >Yeah, it is less maintainable than a simple memcpy() but I did not >find a better alternative. I added a warning above the struct >vm_area_struct definition to update this function every time we change >that structure. Not sure if there is anything else I can do to help >with this. > For !PER_VMA_LOCK, maybe we can use memcpy() as usual. For PER_VMA_LOCK, I just come up the same idea with you:-) >> >> -- >> Wei Yang >> Help you, Help me -- Wei Yang Help you, Help me